Adrenocorticosteroid Pharmacology

Correct Answer

C — Eplerenone

Rationale

Eplerenone is classified as a steroidal mineralocorticoid receptor antagonist with high selectivity — it has no off-target activity at androgen, progesterone, or glucocorticoid receptors. This selectivity profile eliminates the gynecomastia, sexual side effects in men, and menstrual irregularities that result from spironolactone's androgen receptor antagonism. Spironolactone is steroidal but has significant off-target receptor activity. Finerenone is a non-steroidal mineralocorticoid receptor antagonist. Fludrocortisone is a mineralocorticoid receptor agonist used for replacement therapy.

Correct Answer

A — Mifepristone

Rationale

Mifepristone is classified as a competitive glucocorticoid receptor and progesterone receptor antagonist. In Cushing syndrome, it is approved for controlling hyperglycemia in adults with type 2 diabetes or impaired glucose tolerance who are not surgical candidates. Pasireotide is a somatostatin receptor analog that suppresses adrenocorticotropic hormone secretion. Metyrapone and osilodrostat are both CYP11B1 (11-beta-hydroxylase) inhibitors that reduce cortisol synthesis — they act at the enzyme level, not at the receptor.

Correct Answer

D — Osilodrostat

Rationale

Osilodrostat is classified as a potent, selective CYP11B1 (11-beta-hydroxylase) inhibitor approved for Cushing disease not amenable to surgery or with persistent disease after pituitary surgery. It has higher potency and selectivity than metyrapone and was approved in 2020. Mitotane is an adrenocorticolytic agent used primarily for adrenocortical carcinoma. Mifepristone is a glucocorticoid receptor antagonist. Pasireotide is a somatostatin receptor analog that reduces adrenocorticotropic hormone secretion from pituitary adenoma cells.

Correct Answer

B — Pasireotide

Rationale

Pasireotide is classified as a somatostatin receptor analog with preferential binding to subtypes 1, 2, 3, and 5. Its broad somatostatin receptor binding profile — including subtype 5, expressed at high density on corticotroph adenoma cells — allows it to directly suppress adrenocorticotropic hormone secretion from the pituitary adenoma. Mifepristone blocks the glucocorticoid receptor. Osilodrostat inhibits CYP11B1 at the adrenal level. Mitotane produces adrenocortical cytotoxicity and broad steroidogenic enzyme inhibition, primarily for adrenocortical carcinoma.

Correct Answer

C — Etomidate

Rationale

Etomidate is the only parenteral steroidogenesis inhibitor available. At sub-anesthetic intravenous infusion doses (0.03 to 0.1 mg per kilogram per hour), it inhibits CYP11B1, allowing rapid and titratable cortisol suppression in patients with severe Cushing syndrome who are unable to take oral medications — typically those in intensive care unit settings with hypercortisolism from ectopic adrenocorticotropic hormone syndrome awaiting surgery. Metyrapone, osilodrostat, and ketoconazole are all oral agents. Etomidate's parenteral availability and rapid onset make it the only option in this acute setting.

Correct Answer

A — Mitotane

Rationale

Mitotane is classified as an adrenocorticolytic agent — a derivative of the insecticide DDT — used primarily for adrenocortical carcinoma. It produces selective cytotoxic damage to adrenocortical mitochondria and inhibits multiple steroidogenic enzymes, creating dual antitumor and cortisol-lowering effects. Its extremely long half-life (18 to 159 days from adipose accumulation) requires months to reach steady state and months to clear after discontinuation. Etomidate is a parenteral CYP11B1 inhibitor used for acute cortisol suppression. Osilodrostat is a selective CYP11B1 inhibitor for Cushing disease. Metyrapone inhibits CYP11B1 used for Cushing syndrome management and diagnostic testing.

Correct Answer

B — Spironolactone's steroidal structure gives it off-target antagonist activity at androgen receptors, blocking testosterone action in breast tissue and impairing sexual function

Rationale

Spironolactone's steroidal structure produces off-target antagonism at androgen receptors in addition to its intended mineralocorticoid receptor blockade. In breast tissue, androgen receptor antagonism removes the anti-estrogenic counterbalance to estrogen, producing gynecomastia. The same androgen receptor blockade impairs testosterone signaling in tissues governing libido and erectile function. This effect emerges at doses above 50 to 100 mg per day and is the primary reason for switching to eplerenone (selective steroidal antagonist with no androgen receptor activity) or finerenone (non-steroidal) in men who cannot tolerate these effects. Spironolactone does not inhibit CYP17A1, does not block dopamine receptors, and does not cause hypokalemia under therapeutic conditions.

Correct Answer

D — Finerenone's non-steroidal structure provides balanced heart and kidney tissue distribution, no androgen receptor off-target effects, and a shorter half-life that may reduce hyperkalemia risk compared with spironolactone

Rationale

Finerenone's non-steroidal structure confers several pharmacological advantages in diabetic kidney disease. Its tissue distribution is balanced between heart and kidney — unlike spironolactone, which concentrates predominantly in the kidney — providing cardiorenal protection at both sites simultaneously. Its short half-life of 2 to 3 hours reduces sustained mineralocorticoid receptor blockade between doses and may reduce the risk of hyperkalemia relative to longer-acting agents. The absence of off-target androgen receptor activity eliminates gynecomastia and sexual side effects. Finerenone is actually less potent at the mineralocorticoid receptor than spironolactone (spironolactone is approximately 60-fold more potent), and it does not have a monthly dosing interval.

Correct Answer

A — Mineralocorticoid receptor activation in cardiac fibroblasts, vascular endothelial cells, and glomerular mesangial cells promotes fibrosis, endothelial dysfunction, and glomerular inflammation — effects that mineralocorticoid receptor antagonists prevent independently of blood pressure lowering

Rationale

The mineralocorticoid receptor is expressed not only in the distal nephron but also in the heart, vasculature, and kidney mesangial cells and podocytes. In the heart, mineralocorticoid receptor activation promotes cardiac fibrosis through collagen synthesis upregulation and macrophage-driven inflammation. In the vasculature, it reduces nitric oxide bioavailability, impairing endothelial function. In glomerular cells, it drives inflammation and proteinuria independently of blood pressure. Blocking these non-epithelial mineralocorticoid receptor effects provides organ protection beyond diuresis and blood pressure reduction — which is why mineralocorticoid receptor antagonists improve outcomes in heart failure and diabetic kidney disease even in patients already on renin-angiotensin-aldosterone system blockade.

Correct Answer

C — Administer hydrocortisone 100 mg intravenous bolus immediately, then 200 mg per day by infusion, with aggressive normal saline resuscitation — treatment must not be delayed for laboratory results

Rationale

This patient is in adrenal crisis precipitated by the physiological stress of infection. Adrenal crisis is a medical emergency requiring immediate hydrocortisone 100 mg intravenous bolus, followed by 200 mg per day by continuous infusion or 50 mg intravenously every 6 hours, plus aggressive normal saline resuscitation for volume depletion. Treatment must never be delayed for laboratory confirmation in a patient with known adrenal insufficiency and the clinical presentation of crisis. Hemodynamic improvement within 30 to 60 minutes of hydrocortisone confirms the diagnosis. Fludrocortisone is not used acutely because high-dose hydrocortisone has sufficient mineralocorticoid activity. Doubling oral medication is the sick-day rule for mild illness, not for a patient in hemodynamic compromise who may be unable to absorb oral medication.

Correct Answer

B — Metyrapone blocks CYP11B1, causing accumulation of deoxycorticosterone (with mineralocorticoid activity, causing hypertension and edema) and shunting of adrenocorticotropic hormone-stimulated precursors into androgen synthesis (causing acne and hirsutism)

Rationale

Metyrapone inhibits CYP11B1 (11-beta-hydroxylase), blocking conversion of 11-deoxycortisol to cortisol and of deoxycorticosterone to corticosterone. Cortisol deficiency stimulates adrenocorticotropic hormone hypersecretion, driving substrate accumulation proximal to the block. Deoxycorticosterone accumulates and has intrinsic mineralocorticoid activity — activating renal mineralocorticoid receptors to cause sodium retention, hypertension, and edema. Simultaneously, adrenocorticotropic hormone drives excess substrate through CYP17A1 into androgen precursors (dehydroepiandrosterone, androstenedione), causing androgen excess with acne and hirsutism in women. These adverse effects are the direct pharmacological consequence of blocking the biosynthetic pathway at this step and can be used to confirm drug effect biochemically.

Correct Answer

D — Mifepristone blocks glucocorticoid receptor-mediated negative feedback at the pituitary and hypothalamus, causing adrenocorticotropic hormone and cortisol to rise substantially — so elevated urinary free cortisol is an expected pharmacological effect, not a sign of inefficacy

Rationale

Mifepristone blocks glucocorticoid receptors throughout the body, including in the hypothalamus and pituitary where cortisol normally exerts negative feedback on corticotropin-releasing hormone and adrenocorticotropic hormone secretion. With that feedback interrupted, adrenocorticotropic hormone rises substantially, driving increased cortisol synthesis. Urinary free cortisol reflects circulating cortisol concentration — which rises as expected during mifepristone therapy. This makes urinary free cortisol and late-night salivary cortisol unreliable monitoring endpoints. Clinical improvement (resolution of hyperglycemia, weight loss, improved blood pressure) and glycemic parameters are the appropriate efficacy endpoints during mifepristone therapy.

Correct Answer

A — Somatostatin receptor activation in pancreatic islets suppresses both insulin secretion from beta cells and incretin hormone secretion, impairing postprandial glucose disposal through two complementary pathways

Rationale

Pasireotide's broad somatostatin receptor binding profile includes receptors expressed on pancreatic islet cells. Somatostatin receptor activation in the islets suppresses insulin secretion from beta cells, reducing the primary glucose-lowering hormone. It also suppresses incretin hormone secretion (glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide), removing an important amplification signal for postprandial insulin release. The combination of impaired direct insulin secretion and lost incretin potentiation produces hyperglycemia in approximately 70% of patients — often requiring initiation or intensification of antidiabetic therapy. Glucagon-like peptide-1 receptor agonists have been used to partially counteract this effect because they restore the incretin pathway downstream of the somatostatin receptor block.

Correct Answer

C — Hydrocortisone's short plasma half-life of approximately 1.5 hours allows divided dosing that mimics the physiological diurnal cortisol rhythm without prolonged hypothalamic-pituitary-adrenal suppression between doses

Rationale

Hydrocortisone is preferred for adrenal insufficiency replacement because it is structurally identical to endogenous cortisol and its short plasma half-life of approximately 1.5 hours allows a three-times-daily divided dosing regimen (largest dose on waking, smaller doses at mid-morning and early afternoon) that approximates the physiological diurnal cortisol pattern. This avoids the prolonged hypothalamic-pituitary-adrenal suppression from continuous glucocorticoid exposure that longer-acting agents like dexamethasone would produce. Dexamethasone's 36 to 54 hour biologic half-life provides convenient once-daily dosing but eliminates the physiological diurnal variation that divided hydrocortisone dosing preserves. Hydrocortisone does have some mineralocorticoid activity but is insufficient at replacement doses to replace fludrocortisone in primary adrenal insufficiency.

Correct Answer

B — Spironolactone, to block mineralocorticoid receptors and reverse the epithelial sodium channel-mediated sodium retention and potassium wasting driving her hypertension and hypokalemia

Rationale

This patient has primary hyperaldosteronism — excess aldosterone from bilateral adrenal hyperplasia is activating mineralocorticoid receptors in the distal nephron, upregulating epithelial sodium channels, driving sodium and water retention (hypertension) and obligate potassium secretion (hypokalemia). Spironolactone is the drug of choice for medical management of primary hyperaldosteronism: it blocks mineralocorticoid receptors directly, reversing both the sodium retention and potassium wasting independently of aldosterone levels. Because this patient has bilateral disease (not a unilateral adenoma), she will likely require long-term medical management rather than surgery. Eplerenone, while avoiding androgen receptor off-target effects, is pharmacologically correct but 60-fold less potent at the mineralocorticoid receptor — spironolactone remains the standard first-choice for primary hyperaldosteronism medical management.

Correct Answer

D — Hydrocortisone's short half-life requires three divided daily doses that create adrenocorticotropic hormone suppression without continuously elevated glucocorticoid levels, preserving the nocturnal growth hormone surge and linear bone growth that dexamethasone's long half-life would suppress

Rationale

In children with congenital adrenal hyperplasia, the primary concern beyond adrenocorticotropic hormone suppression is preserving normal linear growth. Dexamethasone's long biologic half-life of 36 to 54 hours produces sustained glucocorticoid receptor activation throughout the night, suppressing the nocturnal growth hormone surge that drives skeletal growth. Hydrocortisone's short plasma half-life of approximately 1.5 hours, given in three divided daytime doses, provides adrenocorticotropic hormone suppression during the day while allowing glucocorticoid levels to fall during the night — preserving the nocturnal growth hormone secretion pattern. Dexamethasone is reserved for adults or for children inadequately controlled on hydrocortisone, where the growth concern is no longer the primary limiting factor.

Correct Answer

A — Mifepristone blocks glucocorticoid receptor negative feedback, causing adrenocorticotropic hormone and cortisol to rise substantially; the markedly elevated cortisol then overwhelms 11-beta-hydroxysteroid dehydrogenase type 2 and activates mineralocorticoid receptors, driving renal potassium wasting

Rationale

Mifepristone produces a two-step mechanism leading to hypokalemia. First, by blocking glucocorticoid receptors throughout the body including in the hypothalamus and pituitary, it removes negative feedback on adrenocorticotropic hormone secretion, causing adrenocorticotropic hormone and cortisol to rise substantially during therapy. Second, the markedly elevated circulating cortisol concentrations exceed the capacity of 11-beta-hydroxysteroid dehydrogenase type 2 to convert cortisol to inactive cortisone in the distal nephron — the same enzyme saturation mechanism seen with pharmacological glucocorticoid doses. Cortisol then activates renal mineralocorticoid receptors, driving sodium retention and potassium secretion. This is noted in the module as an expected adverse effect of mifepristone therapy, treated with potassium supplementation and sometimes eplerenone.

Correct Answer

C — Finerenone, because non-steroidal mineralocorticoid receptor antagonism in podocytes and mesangial cells reduces glomerular inflammation and proteinuria independently of blood pressure

Rationale

Finerenone is the only mineralocorticoid receptor antagonist with regulatory approval specifically for cardiorenal protection in diabetic kidney disease (FIDELIO-DKD and FIGARO-DKD trials). In podocytes and mesangial cells, mineralocorticoid receptor activation drives glomerular inflammation, fibrosis, and proteinuria independently of blood pressure — a non-epithelial effect that persists even when renin-angiotensin-aldosterone system blockade is maximized. Finerenone's non-steroidal structure provides balanced heart and kidney tissue distribution, and its evidence base is specifically in the combination of type 2 diabetes, elevated albuminuria, and maximum renin-angiotensin-aldosterone system blockade — exactly this patient's clinical situation. Finerenone is the first mineralocorticoid receptor antagonist with an approved indication in this specific setting, reflecting the trial evidence for its cardiorenal protective effects in diabetic kidney disease beyond what renin-angiotensin-aldosterone system blockade alone provides.