Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 411: All of the following conditions require administration of GnRH agonist in a non-pulsatile manner except?

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

Explanation: ### Explanation The physiological action of **Gonadotropin-Releasing Hormone (GnRH)** depends entirely on its **mode of administration**. This concept is a high-yield favorite for NEET-PG. **1. Why Male Infertility is the Correct Answer:** In **Male Infertility** (specifically due to hypogonadotropic hypogonadism), the goal is to stimulate the pituitary to release FSH and LH. To achieve this, GnRH must be administered in a **pulsatile manner** (mimicking the natural rhythm). * **Non-pulsatile (continuous)** administration causes **down-regulation and desensitization** of GnRH receptors on pituitary gonadotrophs. This leads to a "medical castration" effect, which would worsen infertility. **2. Why the other options are incorrect:** In the following conditions, we want to **suppress** the Pituitary-Gonadal axis. Therefore, **non-pulsatile (continuous)** GnRH agonists (e.g., Leuprolide, Goserelin, Nafarelin) are used: * **Prostate Cancer:** Continuous administration inhibits LH, reducing testosterone levels to castrate levels, which starves the tumor. * **Endometriosis:** By suppressing FSH/LH, it creates a hypoestrogenic state, leading to the atrophy of ectopic endometrial tissue. * **Precocious Puberty:** Continuous GnRH agonists suppress the premature activation of the hypothalamic-pituitary-gonadal axis, delaying bone age advancement and puberty. ### Clinical Pearls for NEET-PG: * **Pulsatile GnRH:** Used for **Infertility** (Male/Female) and **Delayed Puberty**. * **Continuous GnRH:** Used for **Prostate Cancer, Endometriosis, Precocious Puberty, Uterine Fibroids,** and **PCOS**. * **Flare Phenomenon:** Initial continuous administration causes a transient rise in hormones before suppression occurs. This is prevented by co-administering Flutamide in prostate cancer patients.

Question 412: Regarding the action of Raloxifene, which of the following statements is true?

A. Agonist on bone and breast
B. Agonist on bone, antagonist on lipids
C. Agonist on bone, antagonist on endometrium (Correct Answer)
D. Agonist on bone and endometrium

Explanation: Raloxifene is a **Selective Estrogen Receptor Modulator (SERM)** [2,3]. The hallmark of SERMs is their tissue-specific action: they act as estrogen agonists in some tissues and antagonists in others, depending on the recruitment of co-activators or co-repressors to the estrogen receptor [2,3]. 1. **Why Option C is Correct:** * **Bone (Agonist):** Raloxifene mimics estrogen in bone, inhibiting osteoclast activity and increasing bone mineral density. It is FDA-approved for the prevention and treatment of postmenopausal osteoporosis [1,2,3]. * **Endometrium (Antagonist):** Unlike Tamoxifen, Raloxifene acts as an **antagonist** in the uterus. Therefore, it does not increase the risk of endometrial carcinoma, making it safer for the uterine lining [2,3]. 2. **Why Other Options are Incorrect:** * **Option A & B:** Raloxifene is an **antagonist in the breast**, which reduces the risk of invasive breast cancer. Regarding lipids, it acts as an **agonist**, lowering LDL cholesterol (though it does not increase HDL or reduce cardiovascular risk) [1,2,3]. * **Option D:** This describes the profile of **Tamoxifen**, which acts as a partial agonist on the endometrium, leading to a high-yield side effect: an increased risk of endometrial hyperplasia and cancer [3]. **High-Yield Clinical Pearls for NEET-PG:** * **Key Advantage:** Raloxifene = Bone (+) | Breast (-) | Endometrium (-) [2,3]. * **Side Effects:** Most common are **hot flashes** (due to anti-estrogen effect in the CNS) and leg cramps [3]. * **Serious Risk:** Like all SERMs, it increases the risk of **Venous Thromboembolism (VTE)** and deep vein thrombosis. * **Comparison:** Tamoxifen is used primarily for breast cancer; Raloxifene is preferred for osteoporosis in women with a high risk of breast cancer [1,3].

Question 413: Dinoprostone is -

A. PG El
B. PGE2 (Correct Answer)
C. PGF2 alpha
D. PG 12

Explanation: **Explanation:** **Dinoprostone** is the naturally occurring form of **Prostaglandin E2 (PGE2)**. In obstetric practice, it is primarily used for **cervical ripening** and the induction of labor. It works by stimulating the collagenase enzyme in the cervix, which leads to the breakdown of collagen and softening of the cervical tissue, while simultaneously stimulating uterine contractions. **Analysis of Options:** * **Option A (PGE1):** This is **Alprostadil** (used for maintaining ductus arteriosus patency) or **Misoprostol** (a synthetic PGE1 analog used for medical abortion and NSAID-induced ulcer prevention). * **Option B (PGE2):** **Correct.** Dinoprostone is the pharmacological preparation of PGE2. * **Option C (PGF2α):** This refers to **Dinoprost**. Its synthetic analog is **Carboprost** (15-methyl PGF2α), which is a second-line agent for Postpartum Hemorrhage (PPH). * **Option D (PGI2):** This is **Epoprostenol** (Prostacyclin), which acts as a potent vasodilator and inhibitor of platelet aggregation, used primarily in pulmonary hypertension. **High-Yield Clinical Pearls for NEET-PG:** * **Dinoprostone (PGE2):** Available as vaginal gels or inserts. It is the drug of choice for cervical ripening when the Bishop score is unfavorable. * **Contraindication:** It should be avoided in patients with a history of asthma (can cause bronchospasm) or previous Cesarean section (risk of uterine rupture). * **Storage:** Dinoprostone gel requires refrigeration (2-8°C), whereas Misoprostol is stable at room temperature, making Misoprostol more practical in resource-limited settings. * **Latanoprost:** A PGF2α analog used topically for glaucoma.

Question 414: Hypercalcemia is decreased by all of the following EXCEPT:

A. Etidronate
B. Calcitonin
C. Lithium (Correct Answer)
D. Glucocorticoids

Explanation: **Explanation:** The correct answer is **Lithium** because it is a known cause of **hypercalcemia**, rather than a treatment for it. Lithium shifts the set-point of the calcium-sensing receptor (CaSR) in the parathyroid gland, requiring higher serum calcium levels to suppress Parathyroid Hormone (PTH) release. Additionally, it reduces renal calcium excretion. This combination often leads to lithium-induced hyperparathyroidism. **Analysis of Options:** * **Etidronate (Option A):** This is a first-generation bisphosphonate. Bisphosphonates inhibit osteoclast-mediated bone resorption, effectively lowering serum calcium levels. They are a mainstay in treating hypercalcemia of malignancy. * **Calcitonin (Option B):** Produced by the parafollicular C-cells of the thyroid, calcitonin directly inhibits osteoclasts and increases renal calcium excretion. It is used for the rapid (though short-term) reduction of calcium in emergency settings. * **Glucocorticoids (Option D):** Steroids (like Prednisone) decrease intestinal calcium absorption and inhibit cytokine-mediated bone resorption. They are particularly effective in hypercalcemia caused by sarcoidosis, Vitamin D toxicity, or certain lymphomas. **NEET-PG High-Yield Pearls:** * **Lithium Side Effects:** Remember the mnemonic **LITH:** **L**eukocytosis, **I**nsipidus (Nephrogenic Diabetes Insipidus), **T**remors/Teratogenicity (Ebstein's Anomaly), **H**yperparathyroidism/Hypothyroidism. * **Drug of Choice:** For acute severe hypercalcemia, the initial management is vigorous **intravenous hydration with normal saline**, followed by loop diuretics (Furosemide) once hydrated. * **Bisphosphonates:** Zoledronic acid is the most potent bisphosphonate used for hypercalcemia of malignancy.

Question 415: Which vitamin D preparation would be the most appropriate in a patient with poor renal function?

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

Explanation: ### Explanation The correct answer is **Calcitriol (Option B)**. **Underlying Medical Concept:** Vitamin D undergoes a two-step activation process in the body to become biologically active: 1. **First Hydroxylation:** Occurs in the **liver** via the enzyme 25-hydroxylase to form 25-hydroxyvitamin D (Calcifediol). 2. **Second Hydroxylation:** Occurs in the **kidneys** via the enzyme **1-alpha-hydroxylase** to form 1,25-dihydroxyvitamin D (**Calcitriol**). In patients with **poor renal function** (Chronic Kidney Disease), the kidneys cannot perform this second hydroxylation step. Therefore, these patients cannot convert precursor forms of Vitamin D into the active hormone. **Calcitriol**, being the pre-activated form (1,25-(OH)₂D₃), bypasses the need for renal activation and is the treatment of choice. **Analysis of Incorrect Options:** * **Cholecalciferol (A) & Ergocalciferol (C):** These are Vitamin D3 and D2, respectively. They are inactive precursors that require both hepatic and renal hydroxylation. In renal failure, they remain inactive. * **Calcifediol (D):** This is 25-hydroxyvitamin D. While it bypasses the liver, it still requires the renal 1-alpha-hydroxylase enzyme to become active. **NEET-PG High-Yield Pearls:** * **Alfacalcidol:** A synthetic analogue (1-alpha-OH-D3) that requires only hepatic hydroxylation. It is also useful in renal failure because it bypasses the kidney. * **Drug of choice for Vitamin D deficiency in Liver Cirrhosis:** Calcifediol (bypasses the liver). * **Drug of choice for Vitamin D deficiency in Renal Failure:** Calcitriol or Alfacalcidol. * **Paricalcitol:** A calcitriol analogue used specifically to reduce Parathyroid Hormone (PTH) levels in secondary hyperparathyroidism of CKD with less risk of hypercalcemia.

Question 416: Calcitonin is not indicated in which of the following conditions?

A. Paget's disease
B. Thyrotoxicosis (Correct Answer)
C. Hyperparathyroidism
D. Hypervitaminosis D

Explanation: **Explanation:** Calcitonin is a hormone secreted by the parafollicular (C-cells) of the thyroid gland. Its primary physiological role is to lower serum calcium levels by inhibiting osteoclast-mediated bone resorption and increasing renal calcium excretion. **Why Thyrotoxicosis is the Correct Answer:** Thyrotoxicosis (excess thyroid hormone) is not an indication for calcitonin. While severe hyperthyroidism can occasionally cause mild hypercalcemia due to increased bone turnover, the treatment focuses on anti-thyroid drugs (e.g., Carbimazole), beta-blockers, and radioactive iodine. Calcitonin has no role in managing the underlying pathophysiology of thyrotoxicosis. **Analysis of Other Options:** * **Paget’s Disease:** Calcitonin is a second-line treatment (after bisphosphonates). It effectively reduces bone pain and suppresses high bone turnover by inhibiting overactive osteoclasts. * **Hyperparathyroidism & Hypervitaminosis D:** Both conditions result in significant **hypercalcemia**. Calcitonin is indicated for the emergency management of hypercalcemic crises because it provides a rapid (though short-lived) reduction in serum calcium levels. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Acts via GPCRs to inhibit osteoclasts. * **Tachyphylaxis:** A key limitation of calcitonin is the rapid development of tolerance (tachyphylaxis) due to the downregulation of receptors, making it unsuitable for long-term hypercalcemia management. * **Salmon Calcitonin:** Used clinically because it is more potent and has a longer half-life than human calcitonin. * **Route:** Administered parenterally or via nasal spray (common for postmenopausal osteoporosis). * **Tumor Marker:** Serum calcitonin levels are used to monitor **Medullary Carcinoma of the Thyroid**.

Question 417: Which is the fastest-acting antithyroid medication?

A. Potassium iodide (Correct Answer)
B. Propylthiouracil
C. Carbimazole
D. Methimazole

Explanation: **Explanation:** The correct answer is **Potassium Iodide (A)**. **Why it is the fastest-acting:** Potassium iodide (and other iodides like Lugol’s iodine) works via the **Wolff-Chaikoff effect**, where high concentrations of iodine acutely inhibit the organification of iodine and the synthesis of thyroid hormones. More importantly, iodides uniquely **inhibit the release of pre-formed thyroid hormones** from the colloid into the circulation. This effect is rapid, occurring within 24–48 hours, making it the fastest-acting agent to lower serum T3/T4 levels. **Why the other options are incorrect:** * **Propylthiouracil (PTU), Carbimazole, and Methimazole (B, C, D):** These are thioamides. They work by inhibiting the enzyme **thyroid peroxidase (TPO)**, which prevents the synthesis of *new* thyroid hormones. However, they do not block the release of hormones already stored in the thyroid follicle. Consequently, their clinical effect is delayed (usually 1–3 weeks) until the pre-formed hormone stores are depleted. **High-Yield Clinical Pearls for NEET-PG:** * **Thyroid Storm:** Potassium iodide is used in thyroid storm due to its rapid action, but it must be administered **1 hour after** the first dose of thioamides to prevent the "Jod-Basedow" effect (where the iodine is used as fuel for more hormone synthesis). * **Pre-operative use:** Iodides are given 10 days before thyroidectomy because they decrease the **size and vascularity** of the thyroid gland, making surgery safer. * **Escape Phenomenon:** The effect of iodides is transient; the thyroid "escapes" from the Wolff-Chaikoff effect after 10–14 days, leading to a rebound of thyrotoxicosis if used alone. * **PTU vs. Methimazole:** PTU is preferred in the **1st trimester** of pregnancy and thyroid storm (as it also inhibits peripheral conversion of T4 to T3), while Methimazole is the drug of choice for most other cases of hyperthyroidism.

Question 418: Which of the following hormones is administered as pulsatile therapy?

A. Gonadotropin-releasing hormone (GnRH) (Correct Answer)
B. Growth hormone (GH)
C. Follicle-stimulating hormone (FSH)
D. Estrogen

Explanation: **Explanation:** The correct answer is **Gonadotropin-releasing hormone (GnRH)**. The physiological action of GnRH is uniquely dependent on its **mode of administration**. 1. **Why GnRH is the correct answer:** GnRH is naturally released from the hypothalamus in a **pulsatile manner** (every 60–90 minutes). This pulsatility is essential to stimulate the anterior pituitary to secrete LH and FSH. * **Pulsatile administration** (using a portable infusion pump) is used clinically to **induce ovulation** in hypothalamic amenorrhea or to treat **infertility** in Kallmann syndrome. * Conversely, **continuous (non-pulsatile) administration** of GnRH or its long-acting analogs (e.g., Leuprolide, Goserelin) causes **downregulation/desensitization** of GnRH receptors, leading to a "medical castration" effect. This is used in treating prostate cancer, endometriosis, and precocious puberty. 2. **Why other options are incorrect:** * **Growth Hormone (GH):** Administered as a daily subcutaneous injection (usually at night) to mimic the natural nocturnal surge, but not via a pulsatile pump. * **FSH:** Administered as daily injections (e.g., Menotropins or Recombinant FSH) during controlled ovarian stimulation; it does not require pulsatile delivery to be effective. * **Estrogen:** Administered orally, transdermally, or via injection in a cyclical or continuous manner for hormone replacement therapy or contraception. **High-Yield Clinical Pearls for NEET-PG:** * **The "Flare" Phenomenon:** Continuous GnRH therapy initially causes a transient rise in LH/FSH (flare) before downregulation occurs. * **GnRH Analogs:** Leuprolide, Goserelin, Nafarelin, Buserelin. * **GnRH Antagonists:** Cetrorelix, Ganirelix (these cause immediate suppression without the initial flare).

Question 419: Tadalafil acts on Phosphodiesterase 5 and causes accumulation of?

A. cAMP
B. cGMP (Correct Answer)
C. PAF
D. IL 10

Explanation: ### Explanation **Mechanism of Action (Why B is correct):** Tadalafil is a selective inhibitor of **Phosphodiesterase-5 (PDE-5)**. In the corpus cavernosum and pulmonary vasculature, Nitric Oxide (NO) stimulates the enzyme guanylyl cyclase, which converts GTP into **cyclic Guanosine Monophosphate (cGMP)**. cGMP causes smooth muscle relaxation and vasodilation by decreasing intracellular calcium. Normally, PDE-5 breaks down cGMP to terminate this signal. By inhibiting PDE-5, Tadalafil prevents the degradation of cGMP, leading to its **accumulation**. This results in prolonged smooth muscle relaxation, increased blood flow to the penis (treating erectile dysfunction), and reduced pulmonary arterial pressure. **Why other options are incorrect:** * **A. cAMP:** Cyclic Adenosine Monophosphate is the second messenger for PDE-3 and PDE-4 inhibitors (e.g., Milrinone, Cilostazol, or Roflumilast). Tadalafil is specific to PDE-5 and does not significantly affect cAMP levels. * **C. PAF:** Platelet Activating Factor is a phospholipid mediator of inflammation and platelet aggregation; it is not regulated by PDE-5. * **D. IL-10:** Interleukin-10 is an anti-inflammatory cytokine. While some PDE inhibitors have minor immunomodulatory effects, the primary and direct mechanism of Tadalafil is not related to IL-10. **High-Yield Clinical Pearls for NEET-PG:** * **Duration:** Tadalafil has the longest half-life (~17.5 hours) among PDE-5 inhibitors, earning it the nickname **"The Weekend Pill."** * **Other Indications:** Besides Erectile Dysfunction, it is FDA-approved for **Pulmonary Arterial Hypertension (PAH)** and **Benign Prostatic Hyperplasia (BPH)**. * **Contraindication:** Never co-administer with **Nitrates** (e.g., Nitroglycerin) as it can cause life-threatening hypotension due to synergistic increases in cGMP. * **Side Effects:** Headache, dyspepsia, and back pain/myalgia (due to PDE-11 inhibition). Unlike Sildenafil, it has less risk of "blue vision" (cyanopsia) because it has higher selectivity for PDE-5 over PDE-6.

Question 420: Weight loss is seen with all of the following drug classes except?

A. GLP-1 Agonists
B. SGLT-2 Inhibitors
C. Pramlintide
D. DPP-4 inhibitors (Correct Answer)

Explanation: **Explanation:**The core concept behind this question is the metabolic impact of various anti-diabetic drug classes on body weight. **DPP-4 Inhibitors (e.g., Sitagliptin, Vildagliptin):** These drugs work by inhibiting the enzyme dipeptidyl peptidase-4, which degrades endogenous GLP-1. While they increase insulin secretion and decrease glucagon, the physiological levels of GLP-1 achieved are not high enough to significantly delay gastric emptying or induce satiety. Therefore, DPP-4 inhibitors are clinically classified as **weight-neutral**.**Why other options are incorrect:** * **GLP-1 Agonists (e.g., Liraglutide, Semaglutide):** These are potent weight-loss agents [2]. They achieve pharmacological levels of GLP-1, which slows gastric emptying and acts on the hypothalamus to increase satiety [1, 4]. * **SGLT-2 Inhibitors (e.g., Dapagliflozin, Empagliflozin):** These induce weight loss primarily through **caloric loss** (glucosuria) and mild osmotic diuresis. * **Pramlintide:** An amylin analogue used in both Type 1 and Type 2 DM. It reduces weight by slowing gastric emptying and suppressing appetite.**High-Yield Clinical Pearls for NEET-PG:** * **Weight Gainers:** Insulin, Sulfonylureas [3], Thiazolidinediones (TZDs), and Meglitinides. * **Weight Losers:** GLP-1 Agonists (Maximum weight loss) [1, 2, 4], SGLT-2 Inhibitors, and Pramlintide. * **Weight Neutral:** Metformin (though often associated with mild loss) and DPP-4 Inhibitors. * **Drug of choice** for obese diabetics: GLP-1 Agonists [1] or SGLT-2 Inhibitors.

Practice by Chapter

Hypothalamic and Pituitary Hormones

Practice Questions

Thyroid Drugs and Antithyroid Agents

Practice Questions

Insulin and Oral Hypoglycemic Agents

Practice Questions

Adrenocorticosteroids

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Sex Hormones: Estrogens and Progestins

Practice Questions

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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