Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 241: Which of the following is a serious and characteristic adverse effect of Metformin?

A. Lactic acidosis (Correct Answer)
B. Weight gain
C. Hypoglycemia
D. Dilutional hyponatremia

Explanation: **Explanation:** **Metformin**, a Biguanide, is the first-line drug for Type 2 Diabetes Mellitus. Its most serious, though rare, adverse effect is **Lactic Acidosis**. 1. **Why Lactic Acidosis is correct:** Metformin inhibits mitochondrial glycerophosphate dehydrogenase and complex I of the mitochondrial respiratory chain. This leads to an increase in anaerobic metabolism and a decrease in hepatic gluconeogenesis from lactate. Consequently, lactate levels rise. While rare, it is life-threatening and occurs primarily in patients with pre-existing renal impairment, as the drug is excreted unchanged by the kidneys. 2. **Why other options are incorrect:** * **Weight gain:** Unlike Sulfonylureas or Insulin, Metformin is **weight neutral** or often causes modest **weight loss**, making it ideal for obese diabetics. * **Hypoglycemia:** Metformin is an "euglycemic" agent. It does not stimulate insulin release; therefore, it does not cause hypoglycemia when used as monotherapy. * **Dilutional hyponatremia:** This is a characteristic side effect of **Chlorpropamide** (a first-generation sulfonylurea) and sometimes Carbamazepine, due to the SIADH-like effect. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Activates **AMP-activated protein kinase (AMPK)**, leading to decreased hepatic glucose production and improved peripheral insulin sensitivity. * **Contraindication:** Avoid if GFR < 30 mL/min due to the high risk of lactic acidosis. * **Common Side Effect:** Gastrointestinal upset (diarrhea, abdominal cramps) is the most common reason for non-compliance. * **Long-term use:** Can lead to **Vitamin B12 deficiency** due to interference with its absorption in the terminal ileum.

Question 242: Which of the following drugs has visual field defects as an adverse effect?

A. Cabergoline
B. Bromocriptine
C. Pegvisomant (Correct Answer)
D. Leuprolide

Explanation: **Explanation:** **Correct Option: C. Pegvisomant** Pegvisomant is a **Growth Hormone (GH) receptor antagonist** used in the treatment of acromegaly. It works by blocking the peripheral action of GH, thereby reducing the production of Insulin-like Growth Factor-1 (IGF-1). The mechanism behind **visual field defects** with Pegvisomant is unique: because it effectively lowers IGF-1 levels, it removes the negative feedback inhibition on the pituitary gland. This can lead to a compensatory **increase in GH secretion** and, more importantly, potential **growth of the underlying pituitary adenoma**. As the tumor expands (adenoma progression), it can compress the **optic chiasm**, resulting in bitemporal hemianopia or other visual field defects. Regular MRI monitoring of the pituitary is mandatory during therapy. **Incorrect Options:** * **A & B (Cabergoline & Bromocriptine):** These are Dopamine (D2) agonists used to treat prolactinomas and acromegaly. They typically cause **tumor shrinkage**, which helps *improve* visual field defects rather than causing them. * **D (Leuprolide):** This is a GnRH analog used for prostate cancer and precocious puberty. Its side effects are primarily related to hypoestrogenism/hypoandrogenism (e.g., hot flashes, bone loss), not visual field changes. **High-Yield Clinical Pearls for NEET-PG:** * **Pegvisomant:** Most potent drug for normalizing IGF-1 levels in acromegaly. * **Monitoring:** Liver Function Tests (LFTs) must be monitored as it can cause asymptomatic elevation of liver enzymes. * **Acromegaly Treatment Hierarchy:** Surgery is the first line; Somatostatin analogs (Octreotide) are the first-line medical therapy; Pegvisomant is used for resistant cases.

Question 243: A young female presents with a history of intercourse 5 hours prior. Select the drug that can act as a single-dose postcoital contraceptive.

A. Clomiphene citrate
B. Mifepristone (Correct Answer)
C. Danazol
D. Medroxyprogesterone acetate

Explanation: **Explanation:** **Mifepristone (Option B)** is a potent competitive antagonist at progesterone receptors. In the context of emergency contraception, it acts by delaying or inhibiting ovulation (if taken pre-ovulatory) and altering the endometrium to prevent implantation (if taken post-ovulatory). A single dose of **10–25 mg** is highly effective as a postcoital contraceptive and is often preferred due to fewer side effects (like nausea/vomiting) compared to the Yuzpe regimen. **Analysis of Incorrect Options:** * **Clomiphene citrate (A):** A Selective Estrogen Receptor Modulator (SERM) used primarily for **ovulation induction** in infertility; it would be counterproductive in this scenario. * **Danazol (C):** An androgen derivative used in endometriosis and hereditary angioedema. While it was historically used for emergency contraception, it requires multiple doses and is far less effective and more toxic than modern options. * **Medroxyprogesterone acetate (D):** A progestin used for long-term contraception (DMPA injections) or menstrual cycle regulation. It is not used as a single-dose emergency contraceptive. **High-Yield NEET-PG Pearls:** * **Levonorgestrel (LNG):** The most common single-dose emergency contraceptive (1.5 mg) used within 72 hours. * **Ulipristal Acetate:** A Selective Progesterone Receptor Modulator (SPRM) effective up to **120 hours (5 days)** post-intercourse. * **Copper T (IUCD):** The **most effective** emergency contraceptive method if inserted within 5 days. * **Mifepristone Dosing:** 10–25 mg for emergency contraception; 200 mg (combined with Misoprostol) for medical abortion.

Question 244: The clinical use of leuprolide includes all of the following EXCEPT:

A. Endometriosis
B. Osteoporosis (Correct Answer)
C. Prostate cancer
D. Precocious puberty

Explanation: **Explanation:** **Leuprolide** is a synthetic **GnRH (Gonadotropin-Releasing Hormone) analog**. Its clinical effect depends on the mode of administration: * **Pulsatile administration:** Stimulates FSH/LH release (used for infertility) [2][3]. * **Continuous (Long-acting) administration:** Causes initial "flare" followed by down-regulation and desensitization of GnRH receptors in the pituitary [2][3]. This leads to a state of **hypogonadotropic hypogonadism** (decreased estrogen in females and testosterone in males). **Why Osteoporosis is the Correct Answer:** Osteoporosis is a **major side effect** of leuprolide, not a clinical use. By inducing a hypoestrogenic state (similar to menopause), leuprolide decreases bone mineral density. In fact, when used for more than six months, "add-back therapy" (low-dose estrogen/progestin) is often required to prevent bone loss. **Analysis of Incorrect Options:** * **Endometriosis:** Leuprolide suppresses the estrogen that fuels ectopic endometrial tissue growth, providing symptomatic relief. * **Prostate Cancer:** Continuous leuprolide causes "chemical castration" by reducing testosterone levels, which is a mainstay in treating androgen-dependent prostate carcinoma [1]. * **Precocious Puberty:** By suppressing the premature activation of the hypothalamic-pituitary-gonadal axis, leuprolide halts early pubertal development. **Clinical Pearls for NEET-PG:** 1. **Initial Flare:** In prostate cancer, leuprolide causes a transient rise in testosterone [3]. To prevent a "tumor flare" (which can cause spinal cord compression), it is co-administered with **Flutamide** (an androgen receptor blocker) [1]. 2. **Other Uses:** Uterine fibroids (to shrink them before surgery) and advanced breast cancer [1]. 3. **Route:** Usually administered as a long-acting depot injection.

Question 245: Which of the following are androgen receptor antagonists?

A. Cyproterone
B. Spironolactone
C. Flutamide
D. All of these (Correct Answer)

Explanation: **Explanation:** Androgen receptor antagonists (anti-androgens) work by competitively inhibiting the binding of endogenous androgens, like testosterone and dihydrotestosterone (DHT), to their specific nuclear receptors. * **Flutamide:** A pure, non-steroidal anti-androgen. It is primarily used in the management of prostatic carcinoma. Bicalutamide and Nilutamide are newer analogs with longer half-lives. * **Cyproterone Acetate:** A steroid derivative that possesses both anti-androgenic and progestational activity. It inhibits the action of androgens at the receptor level and also suppresses gonadotropin secretion via negative feedback. It is used for precocious puberty, severe acne, and hirsutism in women. * **Spironolactone:** Primarily known as a potassium-sparing diuretic (aldosterone antagonist), it also has significant off-target effects as a weak androgen receptor antagonist and an inhibitor of testosterone synthesis. It is frequently used clinically to treat hirsutism and acne in females. Since all three drugs act by blocking the androgen receptor, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** 1. **Flutamide Side Effect:** Can cause hepatotoxicity; monitoring of LFTs is essential. It also frequently causes gynecomastia. 2. **Finasteride vs. Flutamide:** Do not confuse them. Finasteride is a **5-alpha reductase inhibitor** (blocks conversion of Testosterone to DHT), whereas Flutamide is a **receptor antagonist**. 3. **Enzalutamide:** A second-generation androgen receptor signaling inhibitor used in castration-resistant prostate cancer. 4. **Abiraterone:** Inhibits **CYP17**, blocking the synthesis of androgens in the testes, adrenals, and tumor tissue.

Question 246: All of the following are adverse effects of long-term corticosteroid use EXCEPT?

A. Hypoglycaemia (Correct Answer)
B. Psychosis
C. Peptic ulcers
D. Osteoporosis

Explanation: **Explanation:** **Corticosteroids** are potent metabolic and anti-inflammatory agents. The correct answer is **Hypoglycaemia** because corticosteroids actually cause **Hyperglycaemia**. 1. **Why Hypoglycaemia is the correct answer:** Glucocorticoids (like Prednisolone or Dexamethasone) are "counter-regulatory" hormones. They increase blood glucose levels by stimulating **gluconeogenesis** in the liver and decreasing peripheral glucose uptake in muscles and adipose tissue (anti-insulin effect). Long-term use can lead to "Steroid-induced Diabetes." Therefore, hypoglycaemia is not an adverse effect. 2. **Analysis of Incorrect Options:** * **Psychosis (Option B):** Corticosteroids affect the CNS, leading to "Steroid Psychosis," mood swings, euphoria, or depression. * **Peptic Ulcers (Option C):** They increase gastric acid secretion and decrease protective mucus production, especially when used concurrently with NSAIDs. * **Osteoporosis (Option D):** This is a hallmark side effect. Steroids inhibit osteoblast activity, stimulate osteoclasts, and decrease intestinal calcium absorption, leading to bone loss and pathological fractures. **High-Yield Clinical Pearls for NEET-PG:** * **Cushingoid Features:** Long-term use leads to moon facies, buffalo hump, and truncal obesity. * **Ocular Effects:** Steroids are notorious for causing **Posterior Subcapsular Cataracts** and **Glaucoma** (due to increased intraocular pressure). * **Wound Healing:** They delay healing by inhibiting fibroblast proliferation and collagen synthesis. * **Withdrawal:** Abrupt cessation after long-term use can cause **Acute Adrenal Insufficiency** (Addisonian crisis) due to HPA axis suppression. Always taper the dose.

Question 247: Metyrosine is indicated in which of the following conditions?

A. Malignant pheochromocytoma (Correct Answer)
B. Addison's disease
C. Depression
D. Hypertensive emergency

Explanation: **Explanation:** **Metyrosine (α-methyl-L-tyrosine)** is a competitive inhibitor of the enzyme **Tyrosine Hydroxylase**, which catalyzes the conversion of Tyrosine to DOPA. Since this is the **rate-limiting step** in catecholamine biosynthesis, Metyrosine effectively reduces the production of epinephrine and norepinephrine. **Why Option A is Correct:** In **Malignant Pheochromocytoma**, there is a massive, uncontrolled production of catecholamines. While surgical resection is the primary treatment for benign tumors, malignant or metastatic cases may not be fully resectable. Metyrosine is indicated for the **long-term management** of these patients to decrease catecholamine synthesis, thereby controlling symptoms like severe hypertension and palpitations. It is also used pre-operatively to stabilize patients. **Why Other Options are Incorrect:** * **B. Addison’s Disease:** This is primary adrenocortical insufficiency (deficiency of cortisol/aldosterone). Treatment involves steroid replacement (Hydrocortisone/Fludrocortisone), not inhibition of catecholamines. * **C. Depression:** Metyrosine can actually *cause* or worsen depression as a side effect because it depletes CNS dopamine and norepinephrine. * **D. Hypertensive Emergency:** While Metyrosine lowers blood pressure, it takes time to deplete catecholamine stores. For emergencies, rapid-acting intravenous agents like Labetalol, Nicardipine, or Sodium Nitroprusside are preferred. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Inhibits Tyrosine Hydroxylase (Rate-limiting step). * **Key Side Effects:** Extrapyramidal symptoms (due to dopamine depletion), sedation, and crystalluria (patients must maintain high fluid intake). * **Pheochromocytoma Protocol:** Traditionally, patients are prepared with **Alpha-blockers first** (e.g., Phenoxybenzamine), followed by Beta-blockers to avoid a hypertensive crisis (unopposed alpha stimulation). Metyrosine is added if these are insufficient.

Question 248: Which of the following is NOT a therapeutic use of progesterone?

A. Postponement of menstruation
B. Post-coital pill
C. Treatment of breast tumors (Correct Answer)
D. Treatment of abnormal uterine bleeding

Explanation: **Explanation:** The correct answer is **C. Treatment of breast tumors**. Progesterone and its derivatives (progestins) are generally contraindicated or not used in the treatment of breast tumors because many breast cancers are **progesterone-receptor positive**. Progestins can potentially stimulate the proliferation of these malignant cells. In fact, antiprogestins (like Mifepristone) or hormonal antagonists (like Tamoxifen) are more relevant in breast cancer management. **Analysis of other options:** * **A. Postponement of menstruation:** Administering progestins during the luteal phase maintains the endometrial lining, preventing the withdrawal bleed. Menstruation occurs only after the drug is discontinued. * **B. Post-coital pill:** High-dose progestins (e.g., Levonorgestrel 1.5mg) act as emergency contraception by delaying ovulation and altering cervical mucus to prevent fertilization. * **C. Treatment of abnormal uterine bleeding (AUB):** Progestins are the mainstay for treating AUB caused by "unopposed estrogen" (e.g., PCOS or anovulatory cycles). They stabilize the endometrium and ensure a controlled, synchronized shedding. **High-Yield Clinical Pearls for NEET-PG:** * **Luteal Phase Support:** Progesterone is essential in IVF cycles to support embryo implantation. * **Endometrial Protection:** In Hormone Replacement Therapy (HRT), progestins are added to estrogen to prevent endometrial hyperplasia and carcinoma. * **Diagnostic Use:** The "Progestin Withdrawal Test" is used to evaluate secondary amenorrhea; a positive bleed indicates adequate endogenous estrogen and a functional outflow tract. * **Endometrial Cancer:** While not used for breast cancer, high-dose progestins (Medroxyprogesterone acetate) are used in the palliative treatment of endometrial carcinoma.

Question 249: Both decreased bone resorption and increased bone formation are caused by which of the following agents?

A. Strontium ranelate (Correct Answer)
B. Ibandronate
C. Teriparatide
D. Calcitonin

Explanation: **Explanation:** The correct answer is **Strontium ranelate**. This agent is unique in the management of osteoporosis because it possesses a **dual mechanism of action**. It acts as a "Dual Acting Bone Agent" (DABA) by: 1. **Increasing bone formation:** It stimulates the proliferation of osteoblasts and increases collagen synthesis. 2. **Decreasing bone resorption:** It inhibits osteoclast differentiation and activity while promoting osteoclast apoptosis. This "uncoupling" of bone remodeling—where formation is stimulated while resorption is suppressed—distinguishes it from other drugs that typically only affect one side of the process. **Analysis of Incorrect Options:** * **B. Ibandronate:** This is a **Bisphosphonate**. Bisphosphonates are purely **anti-resorptive** agents; they inhibit osteoclasts but do not stimulate new bone formation. * **C. Teriparatide:** This is a recombinant human PTH analogue. It is a purely **anabolic** agent (at intermittent low doses) that stimulates bone formation. It does not decrease resorption; in fact, long-term use can eventually increase resorption. * **D. Calcitonin:** This is an **anti-resorptive** hormone that directly inhibits osteoclast activity. It has no bone-forming (anabolic) properties. **NEET-PG High-Yield Pearls:** * **Strontium Ranelate Side Effects:** It is associated with an increased risk of **cardiovascular events** (myocardial infarction) and **DRESS syndrome** (Drug Reaction with Eosinophilia and Systemic Symptoms). Due to cardiac risks, its use is now strictly restricted. * **Teriparatide Limit:** Due to the theoretical risk of **osteosarcoma** (seen in rat studies), clinical use is generally limited to a maximum of 24 months. * **Bisphosphonates:** The drug of choice for most osteoporosis cases; watch for **osteonecrosis of the jaw (ONJ)** and atypical subtrochanteric fractures.

Question 250: What is the action of oxytocin in small doses when used as an intravenous infusion in a full-term uterus?

A. Relaxes uterus
B. Induces uterine contractions (Correct Answer)
C. Causes cervical dilatation
D. All of the above

Explanation: **Explanation:** **Correct Answer: B. Induces uterine contractions** Oxytocin is a peptide hormone synthesized in the hypothalamus and released by the posterior pituitary. Its primary pharmacological action on the full-term uterus is the stimulation of rhythmic contractions. * **Mechanism:** Oxytocin acts via G-protein coupled receptors (Gq) to increase intracellular calcium in the myometrium. At **small doses (low-dose IV infusion)**, it increases the frequency and force of uterine contractions, mimicking natural labor. These contractions are followed by complete relaxation, ensuring fetal oxygenation is maintained. **Why other options are incorrect:** * **A. Relaxes uterus:** This is physiologically incorrect. Oxytocin is an oxytocic (stimulant); it never relaxes the myometrium. Drugs that relax the uterus are called tocolytics (e.g., Ritodrine, Nifedipine). * **C. Causes cervical dilatation:** Oxytocin does not have a direct biochemical effect on the cervix. Cervical dilatation is a **secondary result** of the mechanical pressure exerted by the fetal head during oxytocin-induced uterine contractions. For direct cervical ripening, Prostaglandins (PGE2 - Dinoprostone) are used. **High-Yield NEET-PG Pearls:** 1. **Sensitivity:** The uterus is most sensitive to oxytocin at full term due to a massive increase in oxytocin receptor expression. 2. **High Dose Risks:** At high doses, oxytocin can cause **tetanic contractions** (sustained contraction without relaxation), leading to fetal distress or uterine rupture. 3. **ADH-like effect:** Because it is structurally similar to Vasopressin, high-dose oxytocin can cause **water intoxication** and hyponatremia. 4. **Drug of Choice:** Oxytocin is the drug of choice for both **Induction of Labor** and the prevention/treatment of **Postpartum Hemorrhage (PPH)**.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

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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