Medical Pharmacology: Chapter 41 — Anti-Inflammatory Drugs -- Module 4 — Corticosteroid Toxicity, Drug Interactions, and Gout Pharmacology

Chapter 41 — Anti-Inflammatory Drugs — Module 4 — Corticosteroid Toxicity, Drug Interactions, and Gout Pharmacology

1. A 61-year-old woman with systemic lupus erythematosus has been on prednisone 15 mg/day for two years. She takes calcium carbonate 1,000 mg/day and vitamin D 800 IU/day. Routine dual-energy X-ray absorptiometry (DEXA) bone density scan shows lumbar spine T-score of −2.8 and femoral neck T-score of −2.5. She has had no fractures. Her physician notes she was never started on a bisphosphonate. Which of the following is the most appropriate next step in managing her bone health?

A) Continue calcium and vitamin D supplementation at the current doses and repeat DEXA in 12 months; bisphosphonate therapy is not indicated until a fragility fracture has occurred because the FRAX (fracture risk assessment tool) score in patients with GIOP (glucocorticoid-induced osteoporosis) is unreliable without a fracture history.
B) Initiate a bisphosphonate — alendronate or risedronate as first-line oral agents — without further delay; the ACR (American College of Rheumatology) bisphosphonate prophylaxis threshold (prednisone ≥2.5 mg/day for ≥3 months) was met two years ago, and T-scores of −2.5 or below at any site meet the WHO (World Health Organization) definition of osteoporosis, confirming established bone loss that requires active anti-resorptive therapy.
C) Begin teriparatide (a recombinant parathyroid hormone analogue that stimulates bone formation) rather than a bisphosphonate because GIOP is primarily an anabolic defect from osteoblast suppression; bisphosphonates only target osteoclast-mediated resorption and are therefore pharmacologically mismatched to the dominant mechanism of GIOP.
D) Withhold bisphosphonate therapy because the patient is still premenopausal based on her age; bisphosphonates carry a teratogenic risk and are contraindicated in women of childbearing potential regardless of bone density findings.
E) Reduce prednisone immediately to below 2.5 mg/day to eliminate ongoing bone loss before any pharmacological bone protection is initiated; bisphosphonates added during ongoing corticosteroid use are ineffective because glucocorticoid receptor activation continuously overwhelms the anti-resorptive effect.

ANSWER: B

Rationale:

This patient has established glucocorticoid-induced osteoporosis with T-scores of −2.8 (lumbar spine) and −2.5 (femoral neck), both meeting the WHO diagnostic threshold for osteoporosis (T-score ≤ −2.5). She has been on prednisone 15 mg/day — well above the ACR prophylaxis threshold of ≥2.5 mg/day — for two years, meaning the indication for bisphosphonate initiation was established two years ago. That bisphosphonate therapy was never started represents a gap in care that should be corrected immediately. Calcium and vitamin D supplementation, while necessary and correct components of bone health management in all patients on systemic corticosteroids, are insufficient alone to prevent or treat established GIOP. Alendronate 70 mg weekly or risedronate 35 mg weekly (oral agents) are first-line, with zoledronic acid 5 mg IV annually as an alternative for patients unable to tolerate or adhere to oral bisphosphonates. Bisphosphonates have demonstrated efficacy in preventing fractures in patients on glucocorticoids in multiple randomized trials and are guideline-endorsed for this indication.

Option A: Option A is incorrect because bisphosphonate initiation in GIOP does not require a prior fracture; the ACR guidelines recommend prophylaxis based on corticosteroid dose and duration, and established osteoporosis on DEXA is an independent indication for treatment regardless of fracture history.
Option C: Option C is incorrect because while teriparatide has demonstrated efficacy in GIOP and is preferred over bisphosphonates in some high-risk patients (very severe bone loss, multiple fractures), the dominant mechanism of GIOP includes both osteoblast suppression and osteoclast promotion; bisphosphonates are effective at addressing the resorptive component and are the established first-line pharmacotherapy.
Option D: Option D is incorrect because at 61 years of age, this patient is most likely postmenopausal, and even if premenopausal, oral bisphosphonates are not absolutely contraindicated in women of childbearing potential — appropriate counseling about pregnancy avoidance is given; established osteoporosis with T-scores of −2.5 does not warrant withholding therapy on this basis.
Option E: Option E is incorrect because bisphosphonates are effective in attenuating GIOP even during ongoing corticosteroid use; multiple trials confirm fracture reduction and bone density improvement with bisphosphonate co-administration during corticosteroid therapy. Reducing prednisone below 2.5 mg/day may not be clinically possible for a patient with active SLE requiring immunosuppression.

2. A 54-year-old man with HIV (human immunodeficiency virus) infection on a ritonavir-boosted antiretroviral regimen receives a single intraarticular triamcinolone acetonide injection (40 mg) into his right knee for osteoarthritis pain. Six weeks later he presents with central adiposity, facial rounding, easy bruising, and profound fatigue. Laboratory evaluation reveals a morning serum cortisol of less than 1 µg/dL and a subnormal response to ACTH (adrenocorticotropic hormone) stimulation testing. Which of the following best explains this clinical presentation?

A) The triamcinolone injection triggered an autoimmune adrenalitis in this immunocompromised patient; direct glucocorticoid exposure to adrenocortical tissue via retroperitoneal lymphatic channels caused cytotoxic T-cell infiltration and destruction of the zona fasciculata, producing primary adrenal insufficiency.
B) HIV-associated adrenal insufficiency developed coincidentally after the triamcinolone injection; cytomegalovirus adrenalitis is a known complication of advanced HIV and produces primary adrenal insufficiency independent of any corticosteroid exposure, explaining both the cushingoid features (from prior untreated cortisol excess) and the current insufficiency.
C) Triamcinolone acetonide is uniquely absorbed systemically via the synovial membrane without undergoing first-pass metabolism; at 40 mg, it produces sustained supraphysiological plasma levels equivalent to oral prednisone 40 mg/day for 4 to 6 weeks, independent of any drug interaction, explaining HPA (hypothalamic-pituitary-adrenal) suppression in all patients who receive this dose.
D) Ritonavir is a potent CYP3A4 inhibitor; triamcinolone acetonide is a CYP3A4 substrate, and ritonavir's inhibition dramatically reduces its clearance — raising systemic triamcinolone exposure far beyond that expected from an intraarticular dose alone, producing iatrogenic Cushing syndrome with secondary HPA axis suppression and adrenal insufficiency once the depot is exhausted.
E) The ritonavir-boosted regimen contains tenofovir, which inhibits renal glucocorticoid-binding globulin (GBG) secretion; elevated free triamcinolone fraction in plasma caused by reduced GBG levels produces the supraphysiological free corticosteroid exposure responsible for Cushing syndrome and subsequent HPA suppression.

ANSWER: D

Rationale:

This case illustrates one of the most important drug interactions involving corticosteroids in clinical practice — and one that specifically affects patients on ritonavir-containing antiretroviral regimens who receive corticosteroids by any route, including intraarticular injection. Ritonavir is an exceptionally potent inhibitor of CYP3A4, originally developed as an antiretroviral but now used primarily at low doses to pharmacokinetically boost other protease inhibitors. Triamcinolone acetonide, like all synthetic corticosteroids, is a CYP3A4 substrate. Under normal circumstances, an intraarticular triamcinolone injection produces modest and transient systemic absorption with rapid hepatic CYP3A4-mediated clearance, limiting systemic exposure. In a patient on ritonavir, CYP3A4 is profoundly inhibited — triamcinolone clearance is markedly reduced, and the slowly released depot of triamcinolone from the joint acts as a sustained-release systemic corticosteroid source over weeks. The result is prolonged supraphysiological systemic corticosteroid exposure that produces iatrogenic Cushing syndrome (central adiposity, facial rounding, easy bruising) and secondary HPA axis suppression. When the depot is eventually exhausted, the patient is left with a suppressed HPA axis and no exogenous corticosteroid — producing the adrenal insufficiency now manifest as profound fatigue, undetectable cortisol, and subnormal ACTH stimulation response. This same interaction has been documented with inhaled fluticasone (up to 350-fold increase in systemic exposure) and with epidural, intranasal, and intrabursal corticosteroid formulations in ritonavir-treated patients.

Option A: Option A is incorrect because retroperitoneal lymphatic transport of intraarticular triamcinolone causing autoimmune adrenalitis is not a recognized pharmacological mechanism; autoimmune adrenalitis requires lymphocytic infiltration from systemic autoimmune disease, not from local corticosteroid exposure.
Option B: Option B is incorrect because CMV (cytomegalovirus) adrenalitis occurs in severely immunocompromised patients with very low CD4 counts and produces primary adrenal insufficiency, which would present with hyperkalemia, hyponatremia, and hyperpigmentation — not the cushingoid features described. The temporal relationship with triamcinolone injection in a ritonavir-treated patient makes a pharmacokinetic drug interaction the far more likely explanation.
Option C: Option C is incorrect because while intraarticular triamcinolone does produce more systemic absorption than intraarticular methylprednisolone, it does not routinely produce plasma levels equivalent to 40 mg/day oral prednisone for 4 to 6 weeks in patients without CYP3A4 inhibition; the described pharmacokinetics misrepresent the drug's normal systemic exposure profile.
Option E: Option E is incorrect because tenofovir does not inhibit glucocorticoid-binding globulin secretion; GBG is a hepatically produced protein unrelated to renal drug transporters, and tenofovir's nephrotoxicity targets the renal proximal tubule transporters, not hepatic protein synthesis. There is no established interaction between tenofovir and corticosteroid protein binding.

3. A 49-year-old woman with lupus nephritis is on prednisone 40 mg/day and mycophenolate mofetil (an immunosuppressant that inhibits purine synthesis in lymphocytes). Pre-treatment hepatitis B screening four months ago showed HBsAg (hepatitis B surface antigen) negative, anti-HBc total (antibody to hepatitis B core antigen) positive, and anti-HBs (antibody to hepatitis B surface antigen) positive at 38 IU/L. She was monitored without prophylaxis. She now presents with fatigue and right upper quadrant discomfort. ALT (alanine aminotransferase) is 182 U/L (reference <40 U/L), HBsAg is now positive, and HBV DNA (deoxyribonucleic acid) is 45,000 IU/mL. What is the diagnosis and the most appropriate immediate management?

A) This represents HBV (hepatitis B virus) reactivation — the emergence of active HBV replication in a patient with prior resolved infection under immunosuppression, confirmed by new HBsAg positivity and detectable HBV DNA. Antiviral therapy with entecavir 0.5 mg/day or tenofovir disoproxil fumarate should be initiated immediately, and immunosuppression should be continued carefully under close hepatological monitoring rather than abruptly discontinued.
B) This represents de novo HBV infection acquired during immunosuppression; it is pharmacologically unrelated to the prior serological status, and anti-HBV immunoglobulin plus vaccination booster is the appropriate management because this is a primary infection rather than reactivation.
C) The ALT elevation represents mycophenolate mofetil hepatotoxicity rather than HBV reactivation; mycophenolate inhibits inosine monophosphate dehydrogenase in hepatocytes at immunosuppressive doses and produces a characteristic pattern of hepatocellular injury with new HBsAg positivity as a false-positive finding caused by immune complex interference with the immunoassay.
D) The prior anti-HBs titer of 38 IU/L confirms protective immunity that precludes HBV reactivation; HBsAg positivity and HBV DNA represent a laboratory artifact from the immunosuppression-induced loss of anti-HBs causing unmasking of cross-reactive surface antigens from prior vaccination. No antiviral therapy is needed.
E) The findings are consistent with acute delta hepatitis (HDV superinfection) in a patient with unrecognized chronic HBV; the appropriate management is ribavirin 1,200 mg/day combined with pegylated interferon-alpha rather than a nucleotide analogue, because interferons are the only agents effective against HDV replication.

ANSWER: A

Rationale:

This case is a textbook presentation of hepatitis B reactivation (HBVr), a potentially life-threatening complication of immunosuppressive therapy that was predictable and preventable. HBVr is defined as an abrupt increase in HBV replication in a patient with prior resolved or chronic HBV infection, confirmed here by the transition from HBsAg-negative to HBsAg-positive status and the presence of detectable HBV DNA at 45,000 IU/mL with hepatocellular injury (ALT 182 U/L). The prior serological pattern — HBsAg-negative, anti-HBc-positive, anti-HBs-positive — represents resolved HBV infection with detectable surface antibody. This pattern carries reactivation risk under immunosuppression because hepatocytes retain cccDNA (covalently closed circular DNA) indefinitely; when immune surveillance is suppressed by corticosteroids and mycophenolate, cccDNA can be transcriptionally reactivated. Anti-HBs titers, even at 38 IU/L (above the 10 IU/L protective threshold), do not provide absolute protection against reactivation in profoundly immunosuppressed patients — B-cell function is impaired and antibody production is reduced. The correct response is immediate initiation of antiviral therapy with a high-barrier-to-resistance nucleotide analogue (entecavir or tenofovir). Abrupt discontinuation of immunosuppression is specifically avoided because withdrawal of immunosuppression after HBVr can trigger an immune reconstitution inflammatory syndrome with explosive hepatitis flare; careful continuation with hepatology co-management is required.

Option B: Option B is incorrect because the prior anti-HBc positivity indicates prior HBV exposure, not susceptibility to de novo infection; this is reactivation of pre-existing infection, not a new acquisition. Anti-HBV immunoglobulin is used for post-exposure prophylaxis, not for reactivation.
Option C: Option C is incorrect because mycophenolate mofetil does not cause HBsAg seroconversion from negative to positive; this is a specific serological marker of HBV surface antigen expression, and its positivity combined with detectable HBV DNA and hepatocellular injury is unambiguous evidence of viral replication.
Option D: Option D is incorrect because an anti-HBs titer of 38 IU/L does not guarantee protection against reactivation in profoundly immunosuppressed patients; the B-cell compartment responsible for maintaining anti-HBs production is functionally impaired by the combination of mycophenolate and corticosteroids. The described "unmasking of cross-reactive surface antigens" is not a recognized phenomenon.
Option E: Option E is incorrect because HDV superinfection requires existing active HBsAg positivity for viral replication (HDV is an obligate satellite of HBV), and this patient had negative HBsAg four months ago; the timeline and pattern are entirely consistent with HBV reactivation under immunosuppression, not acute delta hepatitis superinfection.

4. A 67-year-old man with recurrent gout has been on allopurinol 300 mg/day for 18 months with a current serum urate of 7.6 mg/dL despite reasonable medication adherence. His eGFR is 72 mL/min per 1.73 m², and 24-hour urinary uric acid collection returns at 520 mg/day (indicating he is an underexcreter). He takes no aspirin or NSAIDs and has no history of cardiovascular disease or nephrolithiasis. Which of the following best describes whether probenecid could be used in this patient and the pharmacological rationale?

A) Probenecid is contraindicated because his urinary uric acid of 520 mg/day exceeds the 450 mg/day safety threshold for uricosuric therapy; any urinary urate above this threshold is associated with a threefold increase in urate nephrolithiasis risk when probenecid is added.
B) Probenecid is inappropriate because allopurinol and probenecid are pharmacodynamic antagonists — allopurinol's reduction of uric acid production reduces the substrate available for probenecid's uricosuric mechanism, making probenecid ineffective when used concurrently with xanthine oxidase inhibitors.
C) Probenecid is appropriate in this patient; his 24-hour urinary uric acid of 520 mg/day confirms he is an underexcreter (not an overproducer), which is the indication for uricosuric therapy. He has no contraindications — eGFR is well above 30 mL/min, no aspirin use (which would block the uricosuric effect), and no history of nephrolithiasis. Probenecid can be added to allopurinol or used as an alternative to achieve the serum urate target.
D) Probenecid cannot be combined with allopurinol because probenecid inhibits the renal tubular secretion of oxypurinol (allopurinol's active metabolite), raising oxypurinol plasma levels to potentially toxic concentrations that increase the risk of allopurinol hypersensitivity syndrome when used together.
E) Probenecid is contraindicated because his eGFR of 72 mL/min per 1.73 m² falls below the threshold of 80 mL/min per 1.73 m² required for adequate uricosuric efficacy; probenecid requires high urine flow to prevent intratubular urate crystal formation and is only approved for patients with eGFR above 80 mL/min.

ANSWER: C

Rationale:

This patient is an ideal candidate for probenecid consideration. The clinical rationale unfolds through systematic assessment of both the indication and the contraindications. Regarding indication: a 24-hour urinary uric acid of 520 mg/day confirms that this patient is an underexcreter — he produces a normal amount of urate but reabsorbs too much from the renal tubule (the most common cause of primary gout, reflecting reduced URAT1/GLUT9 activity or increased reabsorption). Probenecid, by inhibiting URAT1 and GLUT9 transporters in the proximal tubule, directly addresses this mechanism and is pharmacologically well-matched to underexcreters. Regarding contraindications: (1) eGFR 72 mL/min per 1.73 m² — above the absolute threshold of approximately 30 mL/min required for adequate uricosuric efficacy; (2) no aspirin use — which is the critical check, since low-dose aspirin blocks probenecid's uricosuric effect at URAT1; (3) no nephrolithiasis history — urate overproducers (24h urine >800 mg/day) and patients with prior urate stones are at risk from increased urinary urate load; this patient's urine urate of 520 mg/day is well below the overproduction threshold. Probenecid can either be added to his current allopurinol (dual-mechanism approach) or substituted for it, depending on clinical preference.

Option A: Option A is incorrect because the contraindication threshold for probenecid relates to urate overproduction (24h urine >800 mg/day) and prior nephrolithiasis, not a 450 mg/day threshold; 520 mg/day is a normal excretion level consistent with underexcretion and does not represent overproduction.
Option B: Option B is incorrect because allopurinol and probenecid are not pharmacodynamic antagonists; they target different steps in urate metabolism (production vs. excretion) and can be used in combination. Reducing uric acid production with allopurinol while increasing its excretion with probenecid produces additive urate-lowering.
Option D: Option D is incorrect because while probenecid does inhibit renal tubular secretion of oxypurinol to some degree, this interaction does not produce clinically significant toxicity and is not a contraindication to co-administration; the combination is used in clinical practice.
Option E: Option E is incorrect because the absolute eGFR threshold for probenecid efficacy is approximately 30 mL/min, not 80 mL/min; an eGFR of 72 mL/min is well above the threshold at which uricosuric efficacy is maintained.

5. A 72-year-old woman with severe tophaceous gout is four months into a pegloticase infusion course with co-administered methotrexate 15 mg/week. Her pre-infusion serum urate has been consistently below 1 mg/dL, indicating excellent response. She develops persistent nausea attributable to methotrexate and asks to stop it. Her rheumatologist advises against discontinuing methotrexate at this point. Which of the following best explains the pharmacological risk of stopping methotrexate mid-course in this patient?

A) Stopping methotrexate will cause a rebound elevation in serum urate because methotrexate independently inhibits xanthine oxidase through its folate-antagonist mechanism; without methotrexate's additional urate-lowering effect, serum urate may rise back above 6 mg/dL and trigger a gout flare before the next pegloticase infusion.
B) Methotrexate prevents crystal shedding by stabilizing existing monosodium urate (MSU) crystal deposits through inhibition of the NLRP3 (NOD-like receptor family pyrin domain-containing protein 3) inflammasome; stopping it during active treatment will cause crystal destabilization and acute polyarticular attacks at all tophus sites simultaneously.
C) Methotrexate is used to prevent the nephrotoxicity of allantoin produced by pegloticase's uricase activity; without methotrexate's renal protective effects, rapid allantoin accumulation will cause renal tubular precipitation and acute kidney injury within days of discontinuation.
D) Discontinuing methotrexate will cause an immediate and complete loss of pegloticase efficacy because methotrexate is a required co-factor for pegloticase's enzymatic conversion of uric acid to allantoin; without methotrexate maintaining the reducing environment in which pegloticase functions optimally, the uricase reaction is thermodynamically unfavorable.
E) Methotrexate suppresses the adaptive immune response to pegloticase's foreign porcine uricase protein; stopping it mid-course removes ongoing immunosuppression, allowing the immune system to mount an antibody response against pegloticase. Anti-drug antibody (ADA) formation at this stage would accelerate drug clearance, abolish the uricase response (causing serum urate to rise), and dramatically increase the risk of anaphylaxis at the next scheduled infusion.

ANSWER: E

Rationale:

The rationale for co-administering methotrexate with pegloticase is entirely immunological: methotrexate suppresses the T-cell-dependent and B-cell-dependent adaptive immune response to pegloticase's foreign porcine uricase protein and polyethylene glycol (PEG) moiety, reducing the formation of anti-drug antibodies (ADA). This immunosuppression must be maintained throughout the course because the immune system is repeatedly exposed to pegloticase antigen at every biweekly infusion. Discontinuing methotrexate mid-course removes the immunological brake: without ongoing suppression of T-cell help and B-cell activation, the immune system can develop a primary or secondary antibody response against pegloticase. If ADA form, they bind pegloticase and accelerate its clearance, abolishing uricase activity and causing serum urate to rise — confirmed by a pre-infusion serum urate above 6 mg/dL. Critically, ADA-bearing patients who receive subsequent infusions are at dramatically elevated risk of serious infusion reactions including anaphylaxis because the ADA-antigen complexes can trigger complement activation and mast cell degranulation. The clinical protocol specifically monitors pre-infusion serum urate as the ADA surrogate; if it rises above 6 mg/dL, the infusion must be held — not given — to prevent anaphylaxis. The nausea from methotrexate should be managed (dose reduction, folate supplementation, switching to subcutaneous administration, or antiemetics) rather than by stopping the drug entirely during an active pegloticase course.

Option A: Option A is incorrect because methotrexate does not inhibit xanthine oxidase; it inhibits dihydrofolate reductase (DHFR). Methotrexate has no direct urate-lowering effect, and serum urate control in this patient is entirely attributable to pegloticase.
Option B: Option B is incorrect because methotrexate does not stabilize MSU crystal deposits or prevent crystal shedding; crystal dissolution is driven by the sustained low serum urate achieved by pegloticase, and methotrexate has no direct effect on crystal thermodynamics.
Option C: Option C is incorrect because allantoin is highly water-soluble and is efficiently cleared by the kidneys without nephrotoxic accumulation; allantoin nephrotoxicity is not a recognized clinical problem, and methotrexate has no renal protective role in pegloticase therapy.
Option D: Option D is incorrect because methotrexate is not a co-factor for pegloticase's enzymatic activity; pegloticase is a standalone enzyme that functions independently of methotrexate. Their co-administration is immunological, not biochemical.

6. A 45-year-old man with severe steroid-dependent asthma is maintained on high-dose inhaled fluticasone propionate 500 µg twice daily. He develops subacute invasive pulmonary aspergillosis and is started on itraconazole 200 mg twice daily. Three weeks later he presents with weight gain, facial puffiness, central adiposity, easy bruising, and a random plasma cortisol of 0.8 µg/dL. His asthma remains well-controlled. Which of the following best identifies the mechanism of this complication and the most appropriate management?

A) Itraconazole directly activates glucocorticoid receptors as a partial agonist because of structural similarity to corticosteroids; the Cushingoid features result from itraconazole's own glucocorticoid-like activity, and the management is to switch to voriconazole, which lacks this receptor cross-reactivity.
B) Itraconazole is a potent CYP3A4 inhibitor; fluticasone propionate is almost entirely dependent on CYP3A4 for its systemic clearance. Itraconazole dramatically reduces fluticasone metabolism, raising systemic fluticasone exposure to levels that produce iatrogenic Cushing syndrome and HPA (hypothalamic-pituitary-adrenal) axis suppression. Management includes reducing the fluticasone dose, switching to an inhaled corticosteroid less dependent on CYP3A4 such as beclomethasone dipropionate, or replacing itraconazole with an antifungal with lesser CYP3A4 inhibitory potency if clinically appropriate.
C) Itraconazole inhibits adrenal 11β-hydroxylase, reducing endogenous cortisol synthesis and causing secondary adrenal cortex hypertrophy and excessive ACTH-driven production of cortisol precursors with glucocorticoid activity; the management is to supplement with hydrocortisone to suppress ACTH and halt the precursor accumulation.
D) High-dose inhaled fluticasone produces systemic absorption equivalent to oral prednisone 15 mg/day in all patients regardless of concurrent medications; the three-week delay reflects the time required for the adrenal cortex to develop morphological changes visible on imaging; itraconazole is not the causative agent and does not need to be modified.
E) The combination of itraconazole and inhaled fluticasone produces a pharmacodynamic interaction at the airway glucocorticoid receptor — itraconazole sensitizes the receptor by inhibiting its natural desensitization kinase, producing amplified glucocorticoid signaling in both pulmonary tissue and systemically from the swallowed fraction of the inhaled dose.

ANSWER: B

Rationale:

This is a clinically important and well-documented drug interaction that is particularly dangerous because the route of corticosteroid administration — inhaled — gives a false sense of safety. Fluticasone propionate is an inhaled corticosteroid specifically designed to have minimal systemic bioavailability: its low lipid solubility limits gastrointestinal absorption, and the fraction that reaches the systemic circulation undergoes rapid and nearly complete first-pass CYP3A4-mediated hepatic and intestinal wall metabolism. This is the pharmacokinetic mechanism that normally confines fluticasone's effects to the lung. Itraconazole is one of the most potent CYP3A4 inhibitors in clinical use, and it dramatically reduces fluticasone clearance by inhibiting both hepatic CYP3A4 and intestinal wall CYP3A4. The consequence is that systemic fluticasone exposure increases dramatically — with CYP3A4 inhibitors of sufficient potency (ritonavir raises exposure up to 350-fold; itraconazole produces similar but somewhat less extreme increases). The resulting supraphysiological systemic fluticasone levels produce iatrogenic Cushing syndrome (the features described) with full HPA axis suppression (confirmed by the near-zero random cortisol). Management options include reducing the inhaled fluticasone dose to the lowest effective dose, switching to beclomethasone dipropionate (which is less dependent on CYP3A4 for its systemic metabolism and therefore less susceptible to this interaction), or — if antifungal selection permits — using an azole with less potent CYP3A4 inhibition such as fluconazole (though fluconazole is not first-line for aspergillosis).

Option A: Option A is incorrect because itraconazole does not activate glucocorticoid receptors; it is a triazole antifungal that acts on fungal CYP51 (lanosterol 14α-demethylase) to inhibit ergosterol synthesis. Its role in this interaction is entirely pharmacokinetic via CYP3A4 inhibition, not receptor-based. Voriconazole also inhibits CYP3A4 and would not eliminate the problem.
Option C: Option C is incorrect because itraconazole does not inhibit adrenal 11β-hydroxylase in the manner described; while metyrapone and ketoconazole can impair adrenal steroidogenesis, itraconazole's dominant clinical pharmacological effect relevant to this interaction is CYP3A4 inhibition of fluticasone metabolism.
Option D: Option D is incorrect because high-dose inhaled fluticasone does not routinely produce systemic levels equivalent to oral prednisone 15 mg/day in patients without CYP3A4 inhibition; the itraconazole is the critical precipitating factor in this case.
Option E: Option E is incorrect because itraconazole has no pharmacodynamic interaction at the glucocorticoid receptor and does not inhibit receptor desensitization kinases; the mechanism is entirely pharmacokinetic through CYP3A4 inhibition of fluticasone clearance.

7. A 58-year-old man presents to urgent care eight hours after the onset of acute, severe pain and swelling in his right first metatarsophalangeal joint (the large joint at the base of the big toe). He has a history of gout and is not on urate-lowering therapy. His medications are aspirin 81 mg/day (for primary cardiovascular prevention), lisinopril, and metformin. His creatinine clearance is estimated at 85 mL/min. His blood pressure is 138/86 mmHg and there is no history of peptic ulcer disease, heart failure, or prior GI bleeding. Which of the following best represents the most appropriate pharmacological management of this acute attack?

A) Initiate indomethacin 50 mg three times daily for five to seven days; indomethacin is the preferred NSAID for acute gout because it has the most robust trial evidence and superior anti-inflammatory potency compared to other NSAIDs, and his renal function is adequate for NSAID use.
B) Initiate prednisone 40 mg/day for five days; corticosteroids are the preferred first-line treatment for acute gout in patients on ACE (angiotensin-converting enzyme) inhibitors because NSAIDs reduce the antihypertensive efficacy of ACE inhibitors through prostaglandin-mediated renal vasoconstriction, and colchicine is contraindicated with metformin due to OCT2 transporter competition.
C) Initiate allopurinol 100 mg/day immediately to address the underlying hyperuricemia and provide anti-inflammatory benefit; supplementing with analgesic doses of ibuprofen 200 mg as needed is sufficient for pain control during the first 24 hours while allopurinol takes effect.
D) Initiate low-dose colchicine — 1.2 mg immediately followed by 0.6 mg one hour later; this regimen is within the 36-hour efficacy window, avoids the prostaglandin-dependent renal and cardiovascular concerns of NSAID use in a patient on lisinopril and aspirin, and is not contraindicated by any of his current medications or renal function.
E) Withhold all anti-inflammatory treatment and arrange aspiration of the joint for crystal confirmation before initiating pharmacological therapy; empirical treatment without synovial fluid analysis confirmation of MSU (monosodium urate) crystals risks masking an alternative diagnosis such as septic arthritis or pseudogout, and treatment delay of 24 to 48 hours does not affect outcomes.

ANSWER: D

Rationale:

This patient presents within eight hours of attack onset with a clinical picture highly consistent with gout and requires prompt anti-inflammatory therapy. The selection of acute treatment requires navigating several concurrent medication considerations. Low-dose colchicine (1.2 mg immediately followed by 0.6 mg one hour later, the AGREE trial-validated regimen) is the optimal choice for this patient for several reasons: (1) the attack began only eight hours ago, well within the 36-hour window required for maximal colchicine efficacy; (2) his creatinine clearance of 85 mL/min is well above the threshold at which colchicine is dose-adjusted (eGFR <30 mL/min) or contraindicated (eGFR <15 mL/min); (3) none of his medications — aspirin, lisinopril, metformin — are significant pharmacokinetic interactions with colchicine (metformin does not interact via OCT2 with colchicine in the clinically relevant sense); (4) colchicine avoids the prostaglandin-dependent renal effects of NSAIDs, which are more concerning in a patient on an ACE inhibitor (combined NSAID + ACE inhibitor use increases AKI risk through dual impairment of renal autoregulation) and aspirin (GI risk with NSAID combination). While naproxen or celecoxib could be reasonable alternatives given his adequate renal function, colchicine is the cleanest choice given his medication profile.

Option A: Option A is incorrect because while indomethacin is effective for acute gout, it carries the highest GI and CNS (headache, dizziness) adverse effect profile among NSAIDs and is not superior in efficacy to other NSAIDs or to colchicine; in a patient on aspirin and an ACE inhibitor, the dual prostaglandin inhibition risk with any NSAID makes colchicine a preferable choice.
Option B: Option B is incorrect because colchicine is not contraindicated with metformin — there is no clinically significant OCT2 interaction between colchicine and metformin at standard doses. Corticosteroids would worsen blood glucose control in a patient on antidiabetic therapy and are not the preferred first-line choice when colchicine is available and tolerable.
Option C: Option C is incorrect because allopurinol should not be initiated during an acute attack (crystal shedding mechanism would prolong or worsen the attack), has no acute anti-inflammatory properties, and analgesic-dose ibuprofen 200 mg is insufficient for the degree of inflammation in acute gout.
Option E: Option E is incorrect because a clinical diagnosis of gout — typical presentation, known history, classic joint — is sufficient to initiate empirical treatment in urgent care; delaying treatment for 24 to 48 hours to arrange joint aspiration is clinically inappropriate given that rapid treatment initiation improves outcomes and the clinical picture is highly characteristic. Joint aspiration is appropriate when there is genuine diagnostic uncertainty or concern for septic arthritis, which is not indicated here.

8. A 55-year-old woman with rheumatoid arthritis has been on methotrexate 20 mg/week and prednisone 10 mg/day for three years with good disease control. Over the past six weeks she develops progressive proximal muscle weakness affecting the hip flexors and shoulders, difficulty rising from chairs, and myalgia. Serum creatine kinase (CK) is 1,850 U/L (reference 30–200 U/L — approximately 9 times the upper limit of normal). Anti-CCP (anti-cyclic citrullinated peptide) antibodies remain elevated but stable. Which of the following is the most important next step and best explains why steroid myopathy alone cannot account for this presentation?

A) Steroid myopathy is excluded by the elevated CK; it does not cause muscle fiber necrosis and therefore does not produce CK elevation. The differential diagnosis includes methotrexate-induced myopathy, an inflammatory myopathy (polymyositis/dermatomyositis) unmasked or triggered in the rheumatoid arthritis patient, or statin-induced myopathy if a statin were present. Methotrexate should be held, further workup should include anti-Jo-1 and other myositis-specific antibodies, EMG, and consideration of muscle biopsy to establish the diagnosis before deciding on management.
B) The elevated CK confirms steroid myopathy in this patient because prednisone at 10 mg/day for three years causes mitochondrial dysfunction that eventually produces muscle fiber necrosis detectable as CK elevation; the management is to double the prednisone dose to overcome the mitochondrial toxicity threshold.
C) The elevated CK is consistent with steroid myopathy because glucocorticoids at high cumulative doses cause irreversible sarcolemmal damage in type II fibers; a CK of 1,850 U/L falls within the expected range for steroid myopathy from three years of prednisone, and no further workup is required before reducing the prednisone dose.
D) The presentation is consistent with rheumatoid arthritis flare causing synovitis of the hip and shoulder joints, which artificially elevates CK through increased mechanical stress on periarticular muscles; the next step is increasing methotrexate to 25 mg/week and adding hydroxychloroquine to control joint inflammation.
E) Methotrexate is the cause through folate depletion-induced mitochondrial respiratory chain dysfunction; supplementing with folinic acid 5 mg/day will correct the metabolic defect and resolve the myopathy within two weeks without requiring methotrexate dose reduction or muscle biopsy.

ANSWER: A

Rationale:

The most critical pharmacological reasoning in this question is the CK result: steroid myopathy does not cause muscle fiber necrosis. The mechanism of steroid myopathy is selective type II fiber atrophy through glucocorticoid receptor-mediated suppression of muscle protein synthesis and promotion of ubiquitin-proteasome degradation — a process of fiber atrophy without membrane disruption. Creatine kinase is released into the bloodstream when muscle fiber membranes are disrupted (necrosis or severe membrane permeability change), which does not occur in steroid myopathy. A CK of 1,850 U/L (approximately 9 times the upper limit of normal) definitively rules out steroid myopathy as the sole explanation and demands investigation for an alternative myopathic process. In this patient on both methotrexate and prednisone, the differential includes: (1) methotrexate-induced myopathy, which can produce CK elevation through mechanisms related to folate pathway disruption and mitochondrial effects; (2) an inflammatory myopathy (polymyositis) that has developed independently or been unmasked by the RA treatment context — myositis-specific antibodies (anti-Jo-1, anti-Mi-2, anti-MDA5, etc.) should be sent; (3) drug-induced myopathy from another agent not listed. The appropriate immediate step is to hold methotrexate and pursue a structured myopathy workup: myositis-specific autoantibodies, aldolase, EMG, and probable muscle biopsy to distinguish drug-induced from autoimmune inflammatory myopathy.

Option B: Option B is incorrect because steroid myopathy does not produce CK elevation through mitochondrial dysfunction or necrosis at any dose; doubling the prednisone in a patient with an elevated CK of unexplained cause would be potentially harmful.
Option C: Option C is incorrect because a CK of 1,850 U/L is not within the expected range for steroid myopathy — steroid myopathy characteristically produces normal or minimally elevated CK, not values 9 times the upper limit of normal; this finding cannot be attributed to cumulative steroid exposure.
Option D: Option D is incorrect because RA synovitis does not produce CK elevations of this magnitude through mechanical stress on periarticular muscles; CK at 1,850 U/L indicates primary muscle pathology, not secondary periarticular mechanical effects.
Option E: Option E is incorrect because while methotrexate-induced myopathy is in the differential, the mechanism described (folinic acid-reversible mitochondrial respiratory chain dysfunction) oversimplifies the potential etiology and the claim that folinic acid alone will resolve the myopathy within two weeks is not established; the appropriate approach is to hold the methotrexate and investigate, not to empirically supplement and wait.

9. A 66-year-old man with gout and a history of coronary artery bypass graft surgery three years ago has been on allopurinol 400 mg/day for two years. His most recent serum urate is 7.8 mg/dL, and he has had two gout attacks in the past year. His eGFR is 65 mL/min per 1.73 m². His cardiologist asks the rheumatologist whether switching to febuxostat would achieve better urate control. Which of the following best describes the appropriate response?

A) Switching to febuxostat is appropriate because it is a more potent xanthine oxidase inhibitor than allopurinol at all doses, and at 80 mg/day febuxostat reliably achieves serum urate below 6 mg/dL in over 90% of patients regardless of renal function; the cardiovascular risk data apply only to patients with active unstable coronary artery disease, not to stable post-surgical patients.
B) Switching to febuxostat is appropriate and is specifically safer than allopurinol in post-CABG patients because allopurinol's active metabolite oxypurinol has direct cardiotoxic effects on myocardial mitochondria that are avoided with febuxostat; post-CABG patients represent the one population for which febuxostat is preferred over allopurinol as first-line ULT.
C) Febuxostat should not be used as a next step in this patient; a randomized controlled cardiovascular outcomes trial found higher all-cause and cardiovascular mortality with febuxostat compared to allopurinol specifically in patients with established cardiovascular disease, and this patient's prior CABG places him squarely in that category. The appropriate next step is to further titrate allopurinol — doses of 600 to 800 mg/day are safe in his renal function range and frequently achieve the serum urate target in patients who remain above target at 400 mg/day.
D) Febuxostat is appropriate because the cardiovascular mortality signal was observed only in patients who had experienced both prior MI (myocardial infarction) and stroke; a history of CABG without documented MI or stroke does not meet the high-risk definition used in the cardiovascular outcomes trial, and febuxostat can be used safely in this patient.
E) Switching to febuxostat is not appropriate because febuxostat carries an FDA black-box warning prohibiting its use in any patient who has undergone cardiac surgery; the mechanical cardiac manipulation during CABG permanently sensitizes the myocardium to febuxostat's direct cardiotoxic mechanisms, a finding that led to the surgical exclusion in the FDA label.

ANSWER: C

Rationale:

This question requires applying the findings from the CARES (Cardiovascular Safety of Febuxostat and Allopurinol in Patients with Gout and Cardiovascular Morbidities) trial to a specific patient. The CARES trial enrolled patients with gout and established cardiovascular disease and demonstrated higher all-cause mortality and cardiovascular-specific mortality with febuxostat compared to allopurinol. A history of coronary artery bypass graft surgery is unambiguous evidence of established, serious coronary artery disease — the patient clearly meets the high-risk cardiovascular disease definition. In response, the FDA issued a safety communication specifying that febuxostat should be reserved for patients who have failed or are intolerant of allopurinol. This patient has not been dose-optimized: he is on allopurinol 400 mg/day with an eGFR of 65 mL/min per 1.73 m², and the maximum approved dose is 800 mg/day. With an eGFR of 65, the creatinine clearance (approximately 50 to 60 mL/min) supports titrating to 500 or 600 mg/day with careful monitoring; many patients achieve the serum urate target of <6 mg/dL with doses of 400 to 600 mg/day. Febuxostat should only be considered after allopurinol has been optimized at the maximum tolerated dose and still fails to achieve the serum urate target.

Option A: Option A is incorrect because the cardiovascular safety data from the CARES trial apply to patients with established CVD broadly, including stable post-surgical patients — not only those with active unstable coronary disease; the post-CABG cardiovascular risk is well-established and cannot be dismissed based on clinical stability.
Option B: Option B is incorrect because oxypurinol does not have direct cardiotoxic effects on myocardial mitochondria; this is a fabricated mechanism with no pharmacological basis, and post-CABG patients are not a population for which febuxostat is specifically preferred.
Option D: Option D is incorrect because the CARES trial enrolled patients with established CVD broadly — including prior MI, stroke, unstable angina, and coronary revascularization. Post-CABG status represents established coronary disease and falls within the high-risk definition; the trial did not restrict its cardiovascular mortality finding to patients with combined MI plus stroke.
Option E: Option E is incorrect because febuxostat does not carry a black-box warning specifically prohibiting use in post-cardiac-surgery patients; the FDA action was a safety communication recommending reservation for allopurinol failure, not a categorical black-box contraindication based on cardiac surgery history.

10. A 43-year-old renal transplant recipient is on cyclosporine (a calcineurin inhibitor and potent CYP3A4/P-glycoprotein inhibitor) and mycophenolate for immunosuppression. His creatinine clearance is 55 mL/min per 1.73 m² and he has no history of peptic ulcer disease or GI bleeding. He presents with an acute painful swollen right ankle, confirmed as acute gout on clinical grounds. His physician reviews his medication list before selecting acute gout therapy. Which of the following best describes the most appropriate acute treatment in this patient?

A) Indomethacin 50 mg three times daily for five days is the preferred treatment; NSAIDs are safe in renal transplant recipients at creatinine clearances above 50 mL/min per 1.73 m², and indomethacin's prostaglandin inhibition is the preferred mechanism for acute gout in this population because cyclosporine sensitizes the joint to prostaglandin-mediated pain amplification.
B) Low-dose colchicine (1.2 mg + 0.6 mg) is the preferred treatment; while cyclosporine inhibits P-glycoprotein, this interaction is clinically insignificant at the low-dose colchicine regimen because the total dose of 1.8 mg is below the threshold at which P-gp inhibition produces toxic colchicine plasma levels.
C) Allopurinol 100 mg/day should be initiated immediately to lower serum urate and terminate the acute attack; in renal transplant recipients, the anti-inflammatory benefit of acute urate lowering outweighs the risk of crystal shedding because cyclosporine-associated gout is driven by urate overproduction rather than the crystal shedding mechanism.
D) Febuxostat 80 mg/day is the appropriate immediate treatment because it has direct anti-inflammatory properties in addition to xanthine oxidase inhibition, and it does not interact with cyclosporine through any pharmacokinetic pathway relevant to renal transplant management.
E) Systemic corticosteroids — oral prednisone 30 to 40 mg/day for five days, or intraarticular triamcinolone if the attack is monoarticular and accessible — are the preferred treatment; NSAIDs are relatively contraindicated given the reduced renal function and risk of nephrotoxicity in a cyclosporine-treated kidney transplant, and colchicine is generally contraindicated with cyclosporine because cyclosporine's dual CYP3A4 and P-gp inhibition dramatically raises colchicine plasma levels to potentially life-threatening concentrations.

ANSWER: E

Rationale:

Managing acute gout in a renal transplant recipient on cyclosporine requires navigating contraindications to the three standard first-line agents. NSAIDs are relatively to absolutely contraindicated in this patient: renal transplant recipients have a tenuous renal hemodynamic balance dependent on prostaglandin-mediated afferent arteriolar tone, and NSAIDs — by inhibiting COX and reducing intrarenal prostaglandin synthesis — constrict the afferent arteriole and reduce glomerular filtration pressure, risking acute kidney injury and graft dysfunction. This risk is amplified by cyclosporine, which independently causes renal vasoconstriction. A creatinine clearance of 55 mL/min in a transplanted kidney represents a vulnerable organ, not a safe threshold for NSAID use. Colchicine is generally contraindicated with cyclosporine: cyclosporine is a potent inhibitor of both CYP3A4 and P-glycoprotein, the two primary elimination pathways for colchicine. Their concurrent inhibition dramatically raises colchicine plasma concentrations; fatal colchicine toxicity (neuromyopathy, cytopenias, multi-organ failure) has been reported in transplant recipients on cyclosporine. Systemic corticosteroids are therefore the appropriate choice — prednisone 30 to 40 mg/day for five days (noting the physician must balance adding corticosteroid to an already immunosuppressed patient, but the short course is generally well-tolerated), or intraarticular triamcinolone for accessible monoarticular attacks, which avoids systemic effects. IL-1 inhibitors (anakinra) are a further option if corticosteroids are also problematic.

Option A: Option A is incorrect because NSAIDs are relatively to absolutely contraindicated in renal transplant recipients on cyclosporine; the combination of reduced renal reserve and cyclosporine-induced vasoconstriction makes prostaglandin inhibition hazardous to graft function.
Option B: Option B is incorrect because the cyclosporine-colchicine interaction is clinically significant even at the low-dose colchicine regimen; there is no established safe dose threshold for colchicine use with cyclosporine, and life-threatening toxicity has been reported with doses comparable to or below the 1.8 mg regimen in patients on cyclosporine.
Option C: Option C is incorrect because allopurinol should not be initiated during an acute attack — crystal shedding during ULT initiation will worsen the ongoing attack regardless of whether the gout is cyclosporine-associated or idiopathic. Additionally, allopurinol has no acute anti-inflammatory properties.
Option D: Option D is incorrect because febuxostat has no direct anti-inflammatory properties and is a urate-lowering agent, not an acute gout treatment; initiating any ULT during an acute attack exacerbates the inflammation through crystal shedding.

11. A 52-year-old woman with polymyalgia rheumatica (an inflammatory condition of proximal muscles and joints) completed a 10-month course of prednisone 7.5 mg/day, which was recently discontinued without a formal slow taper. Three weeks after stopping, she presents with persistent fatigue, nausea, postural dizziness, and mild diffuse myalgia. Her inflammatory markers are normal (ESR 8 mm/hr, CRP <0.5 mg/L). An 8 AM serum cortisol is 2.1 µg/dL. Her PMR symptoms have not recurred. Which of the following best describes the diagnosis and management?

A) This presentation is consistent with polymyalgia rheumatica relapse despite normal inflammatory markers; ESR and CRP can normalize transiently during immunosuppression and their current normality reflects residual anti-inflammatory drug effect from the recent prednisone course. Prednisone should be restarted at 15 mg/day and tapered over 12 months.
B) The 8 AM serum cortisol of 2.1 µg/dL is below the threshold strongly suggestive of adrenal insufficiency (approximately 3 µg/dL), confirming HPA (hypothalamic-pituitary-adrenal) axis suppression from the prior corticosteroid course; normal inflammatory markers and absence of PMR symptoms exclude disease relapse. Management includes restarting low-dose hydrocortisone (15 to 20 mg/day in divided doses to mimic the cortisol diurnal rhythm), providing sick-day rules for stress dosing during illness or surgery, and planning a very gradual taper over months as adrenal recovery is confirmed.
C) An 8 AM cortisol of 2.1 µg/dL is within the normal range for patients recently withdrawn from corticosteroids; the expected post-taper cortisol nadir is 2 to 5 µg/dL, and this value confirms normal adrenal recovery. No treatment is needed — the symptoms represent corticosteroid withdrawal syndrome and will resolve within two weeks with reassurance and NSAIDs for myalgia.
D) The diagnosis is secondary adrenal insufficiency from HPA axis suppression; primary adrenal insufficiency must be excluded first by measuring plasma ACTH level before initiating hydrocortisone. An ACTH level above 500 pg/mL would confirm Addison disease (primary adrenal insufficiency), which requires both hydrocortisone and fludrocortisone for mineralocorticoid replacement.
E) The symptoms and cortisol value are consistent with adrenocortical carcinoma precipitated by suppression-and-rebound following the prednisone course; urgent adrenal CT imaging and 24-hour urinary cortisol measurement are required before any hormonal replacement is initiated.

ANSWER: B

Rationale:

The clinical picture is diagnostic of secondary adrenal insufficiency from HPA axis suppression following a 10-month course of prednisone 7.5 mg/day that was abruptly discontinued. The 8 AM cortisol of 2.1 µg/dL is below the threshold of approximately 3 µg/dL below which adrenal insufficiency is strongly confirmed without further testing — values below 3 µg/dL on a morning cortisol generally do not require ACTH stimulation testing for diagnosis. The clinical features are fully consistent: postural dizziness (hypotension from mineralocorticoid-deficient states is less prominent in secondary AI but volume depletion occurs), fatigue, nausea, and myalgia are classic secondary adrenal insufficiency symptoms. Critically, the normal inflammatory markers and absent PMR symptoms exclude disease relapse as the cause of her symptoms. The pathophysiology is straightforward: prednisone at 7.5 mg/day — even at this relatively low dose — suppresses endogenous ACTH secretion during chronic administration; after 10 months of continuous suppression, the pituitary-adrenal axis has lost its ability to produce adequate cortisol when the exogenous steroid is removed. Abrupt cessation (rather than a slow structured taper over weeks to months) did not allow the axis time to recover. Management: restart physiological-dose hydrocortisone (not prednisone — hydrocortisone allows more precise physiological dosing at 15 to 20 mg/day in divided doses), educate about sick-day rules (double or triple the dose during intercurrent illness to prevent adrenal crisis), and plan a very slow taper guided by morning cortisol measurements over the next several months as recovery occurs.

Option A: Option A is incorrect because normal ESR and CRP are not consistent with active PMR — these inflammatory markers are highly sensitive for PMR activity and are not routinely normalized by recent prednisone at 7.5 mg/day for only three weeks post-discontinuation. The presentation is adrenal insufficiency, not disease relapse.
Option C: Option C is incorrect because an 8 AM cortisol of 2.1 µg/dL is not within the normal range; values below approximately 3 µg/dL indicate impaired adrenal reserve and require intervention. Calling 2.1 µg/dL "the expected nadir" misrepresents established cortisol reference ranges for the morning sampling.
Option D: Option D is incorrect because this presentation is clearly secondary adrenal insufficiency from exogenous corticosteroid-induced HPA suppression; in secondary AI, ACTH is low (because the pituitary is suppressed), not high. A plasma ACTH above 500 pg/mL would indicate primary adrenal insufficiency (Addison disease), which has a completely different etiology and is not suggested here. Secondary AI from iatrogenic HPA suppression does not cause mineralocorticoid deficiency because the zona glomerulosa remains responsive to RAAS signals and fludrocortisone is not required.
Option E: Option E is incorrect because adrenocortical carcinoma does not present with symptoms of cortisol deficiency following corticosteroid withdrawal; it presents with cortisol excess (Cushing syndrome) from autonomous cortisol production. This clinical scenario has no features suggestive of adrenal malignancy, and urgent CT imaging is not indicated.