Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 401: Lactation is suppressed by which of the following medications?

A. Metaclopramide
B. Opioids
C. Apomorphine (Correct Answer)
D. Haloperidol

Explanation: ### Explanation The regulation of prolactin secretion is primarily under the inhibitory control of **Dopamine**, which acts on **D2 receptors** in the anterior pituitary. Dopamine is often referred to as the Prolactin Inhibiting Hormone (PIH). **Why Apomorphine is Correct:** Apomorphine is a potent **Dopamine agonist**. By stimulating D2 receptors, it mimics the action of endogenous dopamine, thereby inhibiting the release of prolactin from the lactotrophs. Reduced prolactin levels lead to the suppression of lactation. While Bromocriptine and Cabergoline are more commonly used clinically for this purpose, Apomorphine functions via the same pharmacological mechanism. **Analysis of Incorrect Options:** * **Metoclopramide (A) & Haloperidol (D):** Both are **D2 receptor antagonists**. By blocking the inhibitory effect of dopamine, they cause a rise in prolactin levels (hyperprolactinemia), which can lead to galactorrhea (inappropriate milk production) rather than suppression. * **Opioids (B):** Opioids inhibit the release of dopamine from the hypothalamus. By decreasing the "inhibitory brake," they indirectly increase prolactin secretion. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** **Cabergoline** is currently the drug of choice for suppressing lactation and treating prolactinomas due to its higher efficacy and longer half-life compared to Bromocriptine. * **Physiological Inhibitor:** Dopamine is the only major hormone that is primarily regulated by inhibition rather than stimulation. * **Antipsychotic Side Effect:** Hyperprolactinemia is a common side effect of typical antipsychotics (like Haloperidol) and can cause gynecomastia in males and amenorrhea in females.

Question 402: Which of the following drugs halts both macrovascular and microvascular effects of diabetes mellitus?

A. Acarbose
B. Biguanides (Correct Answer)
C. Meglitinide
D. Algaliptin

Explanation: **Explanation:** **Biguanides (Metformin)** are the first-line agents in Type 2 Diabetes Mellitus because they are uniquely cardioprotective. Unlike many other antidiabetics, Metformin reduces **macrovascular complications** (Myocardial Infarction, Stroke) and **microvascular complications** (Retinopathy, Nephropathy, Neuropathy). This is primarily due to its ability to improve insulin sensitivity, reduce LDL/VLDL levels, and decrease plasminogen activator inhibitor-1 (PAI-1), which provides a fibrinolytic benefit. The landmark UKPDS study confirmed Metformin’s role in reducing cardiovascular mortality. **Analysis of Incorrect Options:** * **Acarbose (Alpha-glucosidase inhibitor):** Primarily reduces postprandial hyperglycemia. While it may have some benefit in reducing cardiovascular events (STOP-NIDDM trial), its evidence for halting long-term microvascular complications is significantly weaker than Metformin. * **Meglitinides (Repaglinide):** These are short-acting insulin secretagogues. They effectively control glucose spikes but have not demonstrated a definitive reduction in macrovascular outcomes or long-term mortality. * **Alogliptin (DPP-4 Inhibitor):** While "cardiovascularly safe" (EXAMINE trial), DPP-4 inhibitors generally show a neutral effect on macrovascular outcomes rather than a significant reduction in mortality compared to Metformin or SGLT2 inhibitors. **NEET-PG High-Yield Pearls:** * **Mechanism:** Activates AMP-activated protein kinase (AMPK), leading to decreased hepatic gluconeogenesis. * **Side Effects:** Most common is GI upset; most serious is **Lactic Acidosis** (avoid if Creatinine >1.5 mg/dL). * **Weight Neutrality:** Metformin is often associated with modest weight loss, unlike Sulfonylureas or Insulin which cause weight gain. * **Vitamin Deficiency:** Long-term use can lead to **Vitamin B12 deficiency**.

Question 403: Male gynaecomastia is seen with which of the following?

A. Clomiphene
B. Testosterone
C. Spironolactone (Correct Answer)
D. Tamoxifen

Explanation: **Explanation:** **Spironolactone** is a potassium-sparing diuretic and aldosterone antagonist. It is a notorious cause of drug-induced gynaecomastia due to its multi-modal anti-androgenic effects: 1. **Androgen Receptor Blockade:** It competitively inhibits the binding of dihydrotestosterone (DHT) to its receptors. 2. **Inhibition of Steroidogenesis:** It reduces testosterone synthesis by inhibiting the enzyme 17α-hydroxylase. 3. **Increased Peripheral Conversion:** It enhances the peripheral conversion of testosterone to estradiol. **Analysis of Incorrect Options:** * **Clomiphene:** This is a Selective Estrogen Receptor Modulator (SERM) used to induce ovulation. In males, it is sometimes used off-label to *treat* gynaecomastia or infertility by increasing gonadotropin secretion. * **Testosterone:** While exogenous testosterone can aromatize into estrogen, it is generally used to treat hypogonadism. In the context of NEET-PG, Spironolactone is the classic "textbook" cause of gynaecomastia. * **Tamoxifen:** This is a SERM that acts as an estrogen antagonist in breast tissue. It is actually a primary pharmacological **treatment** for painful gynaecomastia. **Clinical Pearls for NEET-PG:** * **Mnemonic for Gynaecomastia (DISCO):** **D**igoxin, **I**soniazid, **S**pironolactone, **C**imetidine, **O**estrogens/Ketoconazole. * **Eplerenone:** This is a selective aldosterone antagonist that does *not* cause gynaecomastia, making it the preferred alternative if this side effect occurs. * **Cimetidine:** Another high-yield cause; it acts by inhibiting androgen binding and increasing prolactin levels.

Question 404: What is the most potent anti-inflammatory corticosteroid?

A. Hydrocortisone
B. Prednisolone
C. Triamcinolone
D. Dexamethasone (Correct Answer)

Explanation: **Explanation:** The potency of corticosteroids is determined by their affinity for the glucocorticoid receptor and their duration of action. Corticosteroids are generally classified based on their anti-inflammatory (glucocorticoid) potency relative to hydrocortisone. **1. Why Dexamethasone is correct:** Dexamethasone is a long-acting glucocorticoid with the highest anti-inflammatory potency among the options provided. It is approximately **25–30 times more potent** than hydrocortisone. Crucially, it has **zero mineralocorticoid (salt-retaining) activity**, making it ideal for conditions where fluid retention must be avoided, such as cerebral edema. **2. Analysis of Incorrect Options:** * **Hydrocortisone (Option A):** This is the pharmaceutical form of endogenous cortisol. It is the standard reference (potency = 1) but is the **least potent** of the group. It possesses significant mineralocorticoid activity. * **Prednisolone (Option B):** An intermediate-acting steroid. It is approximately **4 times** more potent than hydrocortisone. * **Triamcinolone (Option C):** Also an intermediate-acting steroid. It is slightly more potent than prednisolone (approx. **5 times** more potent than hydrocortisone) but significantly less than dexamethasone. **3. NEET-PG High-Yield Pearls:** * **Potency Hierarchy:** Dexamethasone = Betamethasone (25-30) > Triamcinolone (5) > Prednisolone (4) > Hydrocortisone (1). * **Betamethasone** is the drug of choice for accelerating fetal lung maturity in preterm labor because it has low protein binding, allowing it to cross the placenta efficiently. * **Drug of choice for replacement therapy** in Addison’s disease is Hydrocortisone (due to its balanced glucocorticoid and mineralocorticoid effects). * **Longest acting steroids:** Dexamethasone and Betamethasone (Biological half-life: 36–72 hours).

Question 405: Which of the following is an oxytocin antagonist?

A. Ritodrine
B. Atosiban (Correct Answer)
C. Isoxsuprine
D. Methergine

Explanation: **Explanation:** **Atosiban** is the correct answer because it is a competitive **oxytocin receptor antagonist**. It works by blocking oxytocin receptors in the myometrium, thereby inhibiting uterine contractions. Clinically, it is used as a **tocolytic** agent to delay imminent preterm birth in pregnant women, providing a window to administer corticosteroids for fetal lung maturity. **Analysis of Incorrect Options:** * **Ritodrine & Isoxsuprine (Options A & C):** These are **$\beta_2$-adrenergic agonists**. While they are also used as tocolytics, their mechanism involves stimulating $\beta_2$ receptors to increase intracellular cAMP, leading to uterine relaxation. They are not oxytocin antagonists. * **Methergine (Methylergometrine) (Option D):** This is an **ergot alkaloid**. Unlike Atosiban, it is an **oxytocic** agent (uterine stimulant). It causes intense, prolonged uterine contractions and is used primarily to prevent or treat Postpartum Hemorrhage (PPH). It is strictly contraindicated in pregnancy before delivery. **High-Yield NEET-PG Pearls:** * **Atosiban's Advantage:** It has a more favorable side-effect profile compared to $\beta$-agonists (which cause tachycardia, tremors, and hyperglycemia). * **Drug of Choice (DOC):** Currently, **Nifedipine** (a Calcium Channel Blocker) is often preferred over Atosiban and Ritodrine as a first-line tocolytic due to its oral efficacy and safety profile. * **Contraindication:** Do not use Methergine in patients with **hypertension** or Preeclampsia, as it can cause a dangerous rise in blood pressure.

Question 406: Which of the following is NOT caused by glucocorticoids?

A. Osteoporosis
B. Hypoglycemia (Correct Answer)
C. Peptic ulceration
D. Cataracts

Explanation: Glucocorticoids (like cortisol) are essential metabolic hormones, but their chronic use or excess leads to a distinct pattern of adverse effects. ### **Why Hypoglycemia is the Correct Answer** Glucocorticoids are **diabetogenic**. They **increase blood glucose levels** (Hyperglycemia) through three primary mechanisms: 1. **Increased Gluconeogenesis:** Stimulating the liver to produce glucose from non-carbohydrate sources. 2. **Increased Glycogenolysis:** Breakdown of stored glycogen. 3. **Peripheral Insulin Resistance:** Decreasing glucose uptake by peripheral tissues (muscle and fat). Therefore, they cause **hyperglycemia**, not hypoglycemia. Steroid-induced diabetes is a common clinical complication. ### **Explanation of Incorrect Options** * **A. Osteoporosis:** Glucocorticoids inhibit osteoblast activity, stimulate osteoclasts, and decrease intestinal calcium absorption. This makes osteoporosis the most common drug-induced bone disease. * **C. Peptic Ulceration:** They reduce protective prostaglandin synthesis in the gastric mucosa and can mask the symptoms of a perforation. The risk is significantly higher when combined with NSAIDs. * **D. Cataracts:** Chronic use is a well-known cause of **posterior subcapsular cataracts** and can also increase intraocular pressure (glaucoma). ### **High-Yield NEET-PG Pearls** * **Mnemonic for Side Effects:** "CUSHINGOID" (Cataracts, Ulcers, Skin thinning, Hypertension/Hirsutism, Immunosuppression, Necrosis of femoral head, Glucose elevation, Osteoporosis, Impaired wound healing, Depression/Psychosis). * **Electrolyte Changes:** Glucocorticoids cause **Hypokalemia** and **Hypernatremia** (due to mild mineralocorticoid activity). * **Hematological Effects:** They cause **Lymphopenia** and **Eosinopenia**, but **Neutrophilia** (due to demargination of neutrophils from blood vessel walls).

Question 407: Which of the following is an absolute contraindication to adrenal steroid therapy?

A. Severe hypertension
B. Osteoporosis
C. Diabetes mellitus
D. Cushing's syndrome (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Cushing's syndrome** The fundamental principle of steroid therapy is to avoid exogenous administration when there is already an endogenous excess. **Cushing’s syndrome** is characterized by chronic hypercortisolism. Administering exogenous corticosteroids in this state would exacerbate the clinical manifestations (e.g., central obesity, muscle wasting, skin thinning) and significantly increase the risk of life-threatening complications like hypertensive crisis or severe metabolic derangement. Therefore, it is considered an **absolute contraindication**. **Analysis of Incorrect Options:** * **A, B, and C (Hypertension, Osteoporosis, Diabetes mellitus):** These are **relative contraindications**. While steroids can worsen these conditions (by causing sodium retention, increasing bone resorption, and inducing hyperglycemia), they are not strictly prohibited. If a patient with these comorbidities has a life-threatening or severe inflammatory condition (e.g., Status Asthmaticus or Pemphigus Vulgaris), steroids may still be administered under close monitoring and pharmacological control of the underlying comorbidity. **High-Yield Clinical Pearls for NEET-PG:** * **Other Absolute Contraindications:** Systemic fungal infections (steroids mask symptoms and allow dissemination) and Herpes Simplex Keratitis (risk of corneal perforation). * **Withdrawal:** Long-term steroid therapy must never be stopped abruptly due to **HPA-axis suppression**; doing so can precipitate an acute adrenal crisis. * **Steroid-Induced Myopathy:** Characterized by proximal muscle weakness; notably, the heart muscle is spared. * **Glucocorticoid of choice in pregnancy:** **Prednisolone** (it is inactivated by placental 11β-HSD2, protecting the fetus). If fetal lung maturity is the goal, use **Betamethasone** or **Dexamethasone** as they cross the placenta.

Question 408: All of the following are natural estrogens EXCEPT:

A. Estradiol
B. Ethinylestradiol (Correct Answer)
C. Estriol
D. Estrone

Explanation: **Explanation:** The distinction between natural and synthetic estrogens is a high-yield concept in endocrine pharmacology. **1. Why Ethinylestradiol is the correct answer:** Ethinylestradiol is a **synthetic derivative** of estradiol. It is created by adding an ethinyl group at the C17 position of the steroid nucleus. This structural modification makes the molecule resistant to first-pass metabolism in the liver, significantly increasing its oral bioavailability and potency compared to natural estrogens. This is why it is the most common estrogenic component used in Combined Oral Contraceptive Pills (COCPs). **2. Why the other options are incorrect:** The body naturally produces three major estrogens, often referred to as E1, E2, and E3: * **Estradiol (E2):** The most potent and primary estrogen produced by the ovaries in premenopausal women. * **Estrone (E1):** A weaker estrogen; it is the primary circulating estrogen after menopause, largely derived from the peripheral conversion of androstenedione in adipose tissue. * **Estriol (E3):** The least potent natural estrogen; it is produced in large quantities by the placenta during pregnancy and serves as a marker of fetal well-being. **Clinical Pearls for NEET-PG:** * **Potency Order:** Estradiol (E2) > Estrone (E1) > Estriol (E3). * **Mestranol:** Another synthetic estrogen (a prodrug converted to ethinylestradiol). * **Diethylstilbestrol (DES):** A non-steroidal synthetic estrogen historically linked to clear cell adenocarcinoma of the vagina in daughters of treated women. * **Metabolism:** Natural estrogens have low oral bioavailability due to rapid hepatic metabolism, whereas synthetic estrogens like ethinylestradiol are orally active.

Question 409: Which of the following drugs does not lead to gynecomastia in males?

A. Spironolactone
B. Cimetidine
C. Levodopa (Correct Answer)
D. Clomiphene

Explanation: **Explanation:** Gynecomastia (enlargement of male breast tissue) is a common side effect of drugs that either decrease testosterone levels, block androgen receptors, or increase estrogenic activity. **Why Levodopa is the correct answer:** Levodopa is a precursor to **Dopamine**. Dopamine acts as a Prolactin-Inhibiting Factor (PIF) in the tuberoinfundibular pathway. By increasing dopamine levels, Levodopa **suppresses prolactin secretion**. Since hyperprolactinemia is a cause of gynecomastia, a drug that lowers prolactin (like Levodopa or Bromocriptine) will not cause it. In fact, dopamine agonists are sometimes used to treat certain types of gynecomastia. **Analysis of Incorrect Options:** * **Spironolactone:** A potassium-sparing diuretic that is a notorious cause of gynecomastia. It acts by blocking androgen receptors and inhibiting testosterone synthesis. * **Cimetidine:** An H2-receptor blocker that has anti-androgenic effects (blocks androgen receptors) and increases serum prolactin levels. * **Clomiphene:** An anti-estrogen used for ovulation induction. In males, it can lead to an increase in the LH/FSH ratio, which paradoxically increases peripheral aromatization of androgens to estrogens, leading to gynecomastia. **High-Yield Clinical Pearls for NEET-PG:** To remember the drugs causing gynecomastia, use the mnemonic **"DISCO"**: * **D:** Digoxin * **I:** Isoniazid * **S:** Spironolactone * **C:** Cimetidine / Calcium Channel Blockers * **O:** Oestrogens *Other notable causes:* Ketoconazole (inhibits steroid synthesis), Finasteride, and Marijuana.

Question 410: Progestogens are used for all of the following conditions except:

A. Anovulatory cycles
B. Pubertal menorrhagia
C. Endometrial carcinoma
D. Inhibition of lactation (Correct Answer)

Explanation: **Explanation:** Progestogens are synthetic derivatives of progesterone used primarily to regulate the menstrual cycle, protect the endometrium, and maintain pregnancy. **Why "Inhibition of Lactation" is the correct answer:** Lactation is primarily inhibited by **Dopamine agonists** (e.g., **Cabergoline**, Bromocriptine) which suppress prolactin release from the anterior pituitary. While high doses of Estrogen were historically used to suppress lactation, Progestogens do not have a significant inhibitory effect on milk production. In fact, Progestogen-only pills (POPs) are the preferred hormonal contraceptive during breastfeeding because they do not interfere with the quantity or quality of breast milk, unlike combined pills. **Analysis of other options:** * **Anovulatory cycles:** Progestogens are used to induce "withdrawal bleeding" and regulate cycles in patients with PCOS or other causes of anovulation. * **Pubertal menorrhagia:** Heavy menstrual bleeding in adolescents is often due to an immature hypothalamic-pituitary-ovarian axis leading to anovulation. Progestogens help stabilize the estrogen-primed endometrium and control bleeding. * **Endometrial carcinoma:** High-dose progestogens (e.g., Medroxyprogesterone acetate) are used as palliative therapy in advanced or recurrent endometrial cancer because they antagonize the proliferative effects of estrogen on the endometrium. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of choice for lactation suppression:** Cabergoline (more effective and fewer side effects than Bromocriptine). * **Lactational Amenorrhea Method (LAM):** Effective only if the mother is exclusively breastfeeding and remains amenorrheic (usually up to 6 months). * **Progestogen of choice for Endometriosis:** Dienogest. * **Progestogen used in HRT to prevent endometrial hyperplasia:** Micronized progesterone or Medroxyprogesterone.

Practice by Chapter

Hypothalamic and Pituitary Hormones

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Thyroid Drugs and Antithyroid Agents

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Insulin and Oral Hypoglycemic Agents

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Adrenocorticosteroids

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Sex Hormones: Estrogens and Progestins

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Androgens and Anabolic Steroids

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Hormonal Contraceptives

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Drugs Affecting Calcium Metabolism

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Drugs for Osteoporosis

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Pharmacological Management of Obesity

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