Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 271: What is the mechanism of action of Exenatide?

A. SGLT inhibitor
B. GLP-1 Analogue (Correct Answer)
C. DPP4 inhibitor
D. AMP kinase inhibitor

Explanation: **Exenatide** is a synthetic version of exendin-4, a peptide originally found in the saliva of the Gila monster [2]. It functions as a **GLP-1 (Glucagon-Like Peptide-1) Receptor Agonist (Analogue)** [1, 2]. GLP-1 is an "incretin" hormone that stimulates glucose-dependent insulin secretion from pancreatic beta cells, suppresses inappropriate glucagon secretion, slows gastric emptying, and increases satiety [1, 2]. **Analysis of Options:** * **A. SGLT-2 Inhibitors:** These drugs (e.g., Dapagliflozin, Empagliflozin) act on the proximal convoluted tubule of the kidney to inhibit glucose reabsorption, leading to glucosuria. * **C. DPP-4 Inhibitors:** These drugs (e.g., Sitagliptin, Vildagliptin) prevent the breakdown of *endogenous* GLP-1 by inhibiting the enzyme Dipeptidyl Peptidase-4. While they share the incretin pathway, they are oral drugs, whereas Exenatide is an injectable analogue [1]. * **D. AMP Kinase Inhibitors:** This is the primary mechanism of **Metformin** (a Biguanide), which activates AMP-activated protein kinase (AMPK) to reduce hepatic gluconeogenesis and improve peripheral insulin sensitivity. **High-Yield Clinical Pearls for NEET-PG:** * **Weight Loss:** Unlike sulfonylureas and insulin, GLP-1 analogues cause significant weight loss, making them ideal for obese diabetic patients [2]. * **Route:** Exenatide is administered **subcutaneously** [1, 2]. * **Adverse Effects:** The most common side effect is nausea/vomiting. A rare but serious association is **acute pancreatitis** [2]. It is contraindicated in patients with a history of Medullary Thyroid Carcinoma (MTC) or MEN-2 syndrome. * **Cardiovascular Benefit:** Liraglutide (another GLP-1 analogue) is specifically noted for reducing major adverse cardiovascular events (MACE).

Question 272: All of the following can cause hyperprolactinemia, except?

A. Bromocriptine (Correct Answer)
B. Phenothiazine
C. Methyldopa
D. Metoclopramide

Explanation: ### Explanation **Concept:** Prolactin secretion is under tonic inhibitory control by **Dopamine** (Prolactin Inhibiting Factor) via **D_2 receptors** in the anterior pituitary. Therefore, any drug that increases dopamine activity will decrease prolactin, while drugs that block dopamine or deplete it will cause hyperprolactinemia. **1. Why Bromocriptine is the correct answer:** Bromocriptine is a **Dopamine (D_2) agonist**. By stimulating dopamine receptors, it mimics the inhibitory effect of natural dopamine on lactotrophs, thereby **decreasing** prolactin levels. It is a primary treatment for prolactinomas and galactorrhea. **2. Analysis of Incorrect Options (Causes of Hyperprolactinemia):** * **Phenothiazines (e.g., Chlorpromazine):** These are typical antipsychotics that act as **D_2 receptor antagonists**. By blocking the inhibitory effect of dopamine, they lead to a rise in prolactin. * **Methyldopa:** This centrally acting antihypertensive acts as a **false neurotransmitter** and depletes presynaptic dopamine stores. Reduced dopamine availability leads to disinhibition of prolactin secretion. * **Metoclopramide:** This is a potent **central D_2 receptor antagonist** used as an antiemetic/prokinetic. It frequently causes hyperprolactinemia as a side effect. **Clinical Pearls for NEET-PG:** * **Drug-induced hyperprolactinemia** is a common cause of secondary amenorrhea, galactorrhea, and gynecomastia. * **Other drugs causing hyperprolactinemia:** Reserpine (depletes dopamine), Haloperidol, Risperidone (highest risk among atypicals), and Verapamil. * **Cabergoline** is currently the preferred D_2 agonist over Bromocriptine due to its higher affinity, longer half-life (twice-weekly dosing), and better side-effect profile. * **Physiological causes** to rule out: Pregnancy, lactation, and stress.

Question 273: A patient with benign prostatic hyperplasia is to be treated. Which of the following drugs would be most useful in this condition?

A. Cyproterone acetate
B. Danazol
C. Bicalutamide
D. Finasteride (Correct Answer)

Explanation: **Explanation:** **Finasteride** is the correct answer because it is a selective **5-alpha reductase inhibitor**. In the prostate, this enzyme converts testosterone into **Dihydrotestosterone (DHT)**, which is the primary androgen responsible for prostatic cell proliferation. By inhibiting this conversion, Finasteride reduces the size of the prostate gland (mechanical obstruction), improves urinary flow, and decreases the risk of acute urinary retention. **Analysis of Incorrect Options:** * **Cyproterone acetate:** A steroid with anti-androgenic and progestogenic activity. It blocks androgen receptors and inhibits gonadotropin secretion. It is primarily used for prostate cancer and hirsutism, but its side effect profile (hepatotoxicity) makes it unsuitable for BPH. * **Danazol:** A synthetic steroid that inhibits gonadotropin release. It is used in endometriosis and hereditary angioedema. It has weak androgenic properties, which would be counterproductive in BPH. * **Bicalutamide:** A potent non-steroidal pure androgen receptor antagonist. While it blocks DHT action, it is reserved for the treatment of **Metastatic Prostate Cancer** rather than BPH. **NEET-PG High-Yield Pearls:** * **Finasteride vs. Dutasteride:** Finasteride inhibits Type II 5-alpha reductase, while Dutasteride inhibits both Type I and Type II. * **Clinical Lag:** Unlike alpha-blockers (e.g., Tamsulosin), which work within days, 5-alpha reductase inhibitors take **6–12 months** to significantly reduce prostate volume. * **Other Uses:** Finasteride is also FDA-approved for **Male Pattern Baldness (Androgenetic Alopecia)** at lower doses (1mg). * **PSA Levels:** These drugs can decrease serum PSA levels by approximately 50%; this must be accounted for when screening for prostate cancer.

Question 274: Which of the following is used for medical adrenalectomy?

A. Metyrapone
B. Ketoconazole
C. Aminoglutethimide
D. All of the above (Correct Answer)

Explanation: **Explanation:** The term **"Medical Adrenalectomy"** refers to the use of pharmacological agents to inhibit the synthesis of adrenal steroids (cortisol, aldosterone, and androgens) as an alternative to surgical removal of the gland. This is typically indicated in Cushing’s syndrome (pre-operatively or in inoperable cases) and certain adrenal carcinomas. **Why "All of the above" is correct:** All three listed drugs act as **adrenocortical inhibitors** by blocking specific enzymes in the steroidogenesis pathway: * **Aminoglutethimide:** It inhibits the enzyme **cholesterol side-chain cleavage (CYP11A1)**, which converts cholesterol to pregnenolone. By blocking the very first step of steroid synthesis, it effectively shuts down the production of all adrenal steroids. * **Ketoconazole:** At high doses, this antifungal inhibits several enzymes, primarily **17α-hydroxylase** and **11β-hydroxylase**. It is often the first-line medical treatment for Cushing’s syndrome due to its efficacy. * **Metyrapone:** It is a selective inhibitor of **11β-hydroxylase**, the final step in cortisol synthesis. It is unique because it can be used to test pituitary ACTH reserve. **High-Yield Clinical Pearls for NEET-PG:** 1. **Metyrapone** is the only adrenal inhibitor that can be used during **pregnancy**. 2. **Ketoconazole** is known for causing **hepatotoxicity** and inhibiting androgen synthesis (leading to gynecomastia in males). 3. **Mitotane** is another agent used for medical adrenalectomy; it is specifically **adrenolytic** (causes permanent destruction of adrenocortical cells) and is used primarily in adrenal carcinoma. 4. **Etomidate** (an IV anesthetic) can also inhibit 11β-hydroxylase and is used in severe, acute hypercortisolemia.

Question 275: Which of the following anti-diabetic drugs acts by inhibiting PPAR-gamma?

A. Sulfonylureas
B. Biguanides
C. Thiazolidinediones (Correct Answer)
D. Acarbose

Explanation: **Explanation:** **1. Why Thiazolidinediones (TZDs) are correct:** Thiazolidinediones (e.g., Pioglitazone, Rosiglitazone) are selective agonists for the **Peroxisome Proliferator-Activated Receptor-gamma (PPAR-γ)**, a nuclear receptor found primarily in adipose tissue, muscle, and liver. Activation of PPAR-γ regulates the transcription of genes involved in glucose and lipid metabolism. This leads to increased synthesis of GLUT-4 transporters and decreased free fatty acids, effectively **decreasing insulin resistance** (insulin sensitizers). **2. Why the other options are incorrect:** * **Sulfonylureas (e.g., Glipizide):** These act by blocking **ATP-sensitive K+ channels** on the pancreatic beta-cell membrane, leading to depolarization, calcium influx, and insulin exocytosis. They are insulin secretagogues, not PPAR-γ ligands. * **Biguanides (e.g., Metformin):** The primary mechanism is the activation of **AMP-activated protein kinase (AMPK)**, which inhibits hepatic gluconeogenesis and improves peripheral glucose uptake. * **Acarbose:** This is an **alpha-glucosidase inhibitor** that acts locally in the intestinal brush border to delay the digestion and absorption of carbohydrates, thereby reducing postprandial hyperglycemia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Site of Action:** TZDs primarily act on **Adipose tissue** (different from Metformin, which primarily acts on the Liver). * **Side Effects:** Weight gain, **fluid retention/edema** (contraindicated in NYHA Class III/IV Heart Failure), and increased risk of bone fractures. * **Pioglitazone specific:** It also has some PPAR-alpha activity (improves lipid profile) but has been under scrutiny for a potential (though debated) risk of bladder cancer. * **Lag period:** The clinical effect of TZDs takes **6–12 weeks** to reach maximum potential because they work via gene transcription.

Question 276: What is the primary drug of choice for the treatment of Addison's disease?

A. Hydrocortisone (Correct Answer)
B. Betamethasone
C. Prednisolone
D. Deoxycorticosterone acetate (DOCA)

Explanation: **Explanation:** **Addison’s disease** (Primary Adrenocortical Insufficiency) is characterized by the deficiency of both glucocorticoids and mineralocorticoids. **Why Hydrocortisone is the Correct Answer:** Hydrocortisone (Cortisol) is the drug of choice because it is the **bio-equivalent of endogenous cortisol**. It possesses both glucocorticoid and significant mineralocorticoid activity (potency ratio 1:1). Its short duration of action allows for a "split-dose" regimen (e.g., 2/3rd in the morning and 1/3rd in the evening), which closely mimics the natural **circadian rhythm** of cortisol secretion. **Analysis of Incorrect Options:** * **Betamethasone:** This is a long-acting, highly potent glucocorticoid with **zero mineralocorticoid activity**. It is unsuitable for replacement therapy in Addison’s as it would not address the aldosterone deficiency and can cause severe suppression of the HPA axis. * **Prednisolone:** While it has some mineralocorticoid activity, it is primarily an intermediate-acting glucocorticoid. It is more commonly used for chronic inflammatory conditions rather than physiological replacement in Addison's. * **Deoxycorticosterone acetate (DOCA):** This is a pure mineralocorticoid. While it helps with salt retention, it lacks the glucocorticoid activity essential for glucose metabolism and stress response. **High-Yield Clinical Pearls for NEET-PG:** * **Fludrocortisone:** If hydrocortisone alone does not sufficiently manage electrolyte balance (hyponatremia/hyperkalemia), **Fludrocortisone** (a potent oral mineralocorticoid) is added to the regimen. * **Stress Dosing:** In patients with Addison’s, the dose of hydrocortisone must be **doubled or tripled** during periods of minor stress (fever, infection) and increased up to 10-fold during major surgery to prevent an **Addisonian Crisis**. * **Diagnosis:** The gold standard for diagnosis is the **ACTH Stimulation Test** (Cosyntropin test).

Question 277: Which of the following dopamine agonists can be used to treat diabetes mellitus?

A. Bromocriptine (Correct Answer)
B. Ropinirole
C. Cabergoline
D. Selegiline

Explanation: **Explanation:** **Bromocriptine** is a dopamine (D2) receptor agonist traditionally used for prolactinomas and Parkinson’s disease. However, a specific **quick-release (QR) formulation** of Bromocriptine is FDA-approved for the treatment of **Type 2 Diabetes Mellitus**. **Mechanism in Diabetes:** The underlying concept involves the **circadian rhythm**. Patients with insulin resistance often have low hypothalamic dopaminergic tone in the morning. Administering Bromocriptine QR within two hours of waking resets the dopaminergic clock, leading to a reduction in hepatic glucose production, decreased free fatty acid levels, and improved insulin sensitivity without increasing insulin levels. **Analysis of Incorrect Options:** * **B. Ropinirole:** A non-ergot dopamine agonist used primarily for Parkinson’s disease and Restless Leg Syndrome. It has no clinical role in glycemic control. * **C. Cabergoline:** While it is a more potent and longer-acting D2 agonist than Bromocriptine (preferred for prolactinomas), it is not approved or used for treating diabetes. * **D. Selegiline:** This is a selective **MAO-B inhibitor** used in Parkinson’s disease to prevent dopamine breakdown; it is not a direct dopamine agonist. **High-Yield Clinical Pearls for NEET-PG:** * **Bromocriptine QR** is the only dopamine agonist approved for T2DM. * **Benefit:** It does not cause hypoglycemia or weight gain (weight neutral). * **Side Effects:** Nausea, dizziness, and orthostatic hypotension are common during initiation. * **Contraindication:** It should be avoided in patients with syncopal migraines or those taking antipsychotic medications (dopamine antagonists).

Question 278: Which among the following is not a SERM?

A. Flutamide (Correct Answer)
B. Ormeloxifene
C. Tamoxifen
D. Raloxifene

Explanation: ### Explanation **Correct Answer: A. Flutamide** **1. Why Flutamide is the correct answer:** **Flutamide** is a non-steroidal **pure anti-androgen**, not a Selective Estrogen Receptor Modulator (SERM) [2]. It works by competitively inhibiting the binding of dihydrotestosterone (DHT) to androgen receptors. It is primarily used in the management of **prostate cancer** to block the effects of testosterone. **2. Analysis of Incorrect Options (SERMs):** SERMs are compounds that act as estrogen receptor agonists in some tissues (e.g., bone, liver) while acting as antagonists in others (e.g., breast, endometrium) [1]. * **B. Ormeloxifene (Centchroman):** A non-steroidal SERM developed in India (CDRI, Lucknow). It is used as a **once-a-week oral contraceptive** (Saheli) and for dysfunctional uterine bleeding. It has potent anti-estrogenic action on the uterus. * **C. Tamoxifen:** The "gold standard" SERM used in the treatment and prophylaxis of **ER-positive breast cancer** [1]. It acts as an antagonist in the breast but as an **agonist in the bone and endometrium** (increasing the risk of endometrial carcinoma) [1], [3]. * **D. Raloxifene:** A second-generation SERM used primarily for **postmenopausal osteoporosis** [1]. It acts as an agonist in the bone but, unlike tamoxifen, it is an **antagonist in the endometrium**, thus carrying no risk of uterine cancer [1]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Clomiphene Citrate** is another SERM used for **ovulation induction** by inhibiting negative feedback at the hypothalamus [1]. * **Bazedoxifene** is a newer SERM used in combination with conjugated estrogens for menopausal symptoms. * **Toremifene** is a tamoxifen analogue with a similar profile used for metastatic breast cancer [1]. * **Mnemonic for Flutamide:** Remember "Flu-**T**-amide" for **T**estosterone/Androgen blockade.

Question 279: A young female presented with amenorrhea, infertility, and galactorrhea. She was treated with a drug that successfully restored ovulation and menstruation. The drug was administered orally. Which of the following drugs was most likely used to treat this patient?

A. Bromocriptine (Correct Answer)
B. Desmopressin
C. Human gonadotropin hormone
D. Leuprolide

Explanation: ### Explanation **1. Why Bromocriptine is Correct:** The patient presents with the classic triad of **Hyperprolactinemia**: amenorrhea, infertility, and galactorrhea. High levels of prolactin inhibit the pulsatile release of GnRH (Gonadotropin-Releasing Hormone), leading to decreased FSH and LH, which results in anovulation and amenorrhea. **Bromocriptine** is a potent **Dopamine (D2) receptor agonist**. Since dopamine is the natural "prolactin-inhibiting factor," Bromocriptine suppresses prolactin secretion from the anterior pituitary. This restores the GnRH pulse generator, thereby normalizing the menstrual cycle and restoring fertility. It is effective when administered orally. **2. Why the Other Options are Incorrect:** * **Desmopressin (B):** An ADH analogue used primarily for Diabetes Insipidus and nocturnal enuresis. It has no effect on the prolactin or reproductive axis. * **Human Gonadotropin Hormone (C):** While hCG/hMG can induce ovulation, they do not treat the underlying galactorrhea or the cause of hyperprolactinemia. Furthermore, they are typically administered via injection, not orally. * **Leuprolide (D):** A GnRH agonist. Continuous administration causes downregulation of GnRH receptors, leading to a "medical oophorectomy" state. This would worsen amenorrhea and infertility rather than treat it. **3. Clinical Pearls for NEET-PG:** * **Drug of Choice:** While Bromocriptine is a classic answer, **Cabergoline** is now the preferred first-line agent for prolactinomas due to its higher efficacy, longer half-life (twice-weekly dosing), and better side-effect profile. * **Side Effects:** Bromocriptine often causes nausea, vomiting, and orthostatic hypotension (start with low doses at bedtime). * **Ergot Derivative:** Both Bromocriptine and Cabergoline are ergot derivatives. A non-ergot alternative is Quinagolide. * **Visual Fields:** Always check for bitemporal hemianopia in these patients to rule out a pituitary macroadenoma compressing the optic chiasm.

Question 280: A child has been diagnosed with vitamin D dependent rickets. What is the most appropriate vitamin D preparation for this condition?

A. Calciferol
B. Cholecalciferol
C. Calcifediol
D. Calcitriol (Correct Answer)

Explanation: **Explanation:** **Vitamin D Dependent Rickets (VDDR)** is a genetic disorder that interferes with the activation of Vitamin D. There are two primary types: * **Type I:** Deficiency of the enzyme **1-alpha-hydroxylase** in the kidney, which converts calcifediol to the active form [1]. * **Type II:** Resistance to the action of Vitamin D due to **mutations in the Vitamin D receptor (VDR)** [1]. **Why Calcitriol is the Correct Answer:** In both types of VDDR, the body cannot effectively produce or utilize the active metabolite of Vitamin D. **Calcitriol (1,25-dihydroxyvitamin D3)** is the active form of Vitamin D [1]. By administering Calcitriol, we bypass the need for renal 1-alpha-hydroxylation (essential for Type I) and provide high doses of the active ligand to overcome receptor resistance (in Type II) [1]. **Analysis of Incorrect Options:** * **A & B (Calciferol/Cholecalciferol):** These are inactive precursors (Vitamin D2/D3). They require both hepatic and renal hydroxylation to become active. * **C (Calcifediol):** This is 25-hydroxyvitamin D3. While it has undergone hepatic hydroxylation, it still requires the 1-alpha-hydroxylase enzyme in the kidney to become Calcitriol. **High-Yield Clinical Pearls for NEET-PG:** * **Active Form:** Calcitriol is the preferred preparation in **Chronic Kidney Disease (CKD)** and **Hypoparathyroidism** because these conditions also lack 1-alpha-hydroxylase activity [1]. * **Storage Form:** 25-OH Vitamin D (Calcifediol) is the major circulating form and the best indicator of a patient's Vitamin D status [2]. * **Nutritional Rickets:** Treated with Cholecalciferol (D3), as the metabolic machinery is intact [2].

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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