Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 131: All of the following are risk factors for increased lactic acidosis in patients on metformin therapy except?

A. Advanced age
B. Liver dysfunction
C. Renal dysfunction
D. Smoking (Correct Answer)

Explanation: **Explanation:** Metformin, a biguanide, is the first-line treatment for Type 2 Diabetes Mellitus. Its most serious, though rare, side effect is **Metformin-Associated Lactic Acidosis (MALA)**. This occurs because metformin inhibits mitochondrial glycerophosphate dehydrogenase and complex I of the electron transport chain, leading to decreased gluconeogenesis from lactate and a subsequent shift toward anaerobic metabolism. **Why Smoking is the Correct Answer:** Smoking is not a risk factor for lactic acidosis. While smoking increases cardiovascular risk in diabetics, it does not interfere with the metabolic clearance of metformin or the production/clearance of lactate. **Why the other options are incorrect:** * **Renal Dysfunction (Option C):** This is the **most significant** risk factor. Metformin is excreted unchanged by the kidneys. Impaired renal function (typically eGFR <30 ml/min) leads to drug accumulation and toxic levels, precipitating lactic acidosis. * **Liver Dysfunction (Option B):** The liver is the primary organ responsible for lactate clearance (via the Cori cycle). Hepatic impairment reduces the body's ability to utilize lactate, increasing the risk of accumulation. * **Advanced Age (Option A):** Elderly patients often have a physiological decline in GFR and are more prone to episodes of dehydration or heart failure, indirectly increasing the risk of metformin accumulation and tissue hypoxia. **High-Yield Clinical Pearls for NEET-PG:** 1. **Mechanism:** Activates AMP-activated protein kinase (AMPK), decreasing hepatic glucose production. 2. **Contraindication:** Metformin should be withheld before major surgery or IV contrast studies (due to risk of contrast-induced nephropathy). 3. **Vitamin Deficiency:** Long-term use is associated with **Vitamin B12 deficiency** (megaloblastic anemia). 4. **Weight Effect:** It is weight-neutral or causes modest weight loss, unlike sulfonylureas or insulin.

Question 132: Which of the following is NOT caused by oestrogen?

A. Weight gain
B. Fluid and water retention
C. Disappearance of comedones
D. None of the above (Correct Answer)

Explanation: The correct answer is **None of the above** because all three listed effects (weight gain, fluid retention, and the disappearance of comedones) are well-documented physiological or pharmacological actions of oestrogen. **1. Weight Gain and Fluid/Water Retention (Options A & B):** Oestrogens promote salt and water retention by the kidneys. This occurs through the stimulation of the **Renin-Angiotensin-Aldosterone System (RAAS)** and a direct effect on renal tubules [1]. This fluid retention often manifests as cyclical edema or breast tenderness and contributes significantly to the weight gain observed in patients on Oral Contraceptive Pills (OCPs) or Hormone Replacement Therapy (HRT) [2]. Additionally, oestrogen has mild anabolic effects that can increase subcutaneous fat deposition. **2. Disappearance of Comedones (Option C):** Oestrogens are effectively "anti-acne" agents. They suppress the production of **androgens** from the ovaries and increase **Sex Hormone Binding Globulin (SHBG)** levels [1]. Higher SHBG binds free testosterone, reducing its availability at the sebaceous glands. This leads to decreased sebum production and the disappearance of comedones (acne). This is why certain OCPs (e.g., those containing Cyproterone acetate or Drospirenone) are FDA-approved for treating acne. **Clinical Pearls for NEET-PG:** * **Metabolic Impact:** Oestrogens increase plasma triglycerides and HDL ("good" cholesterol) while decreasing LDL [1]. * **Coagulation:** Oestrogens increase the synthesis of clotting factors (II, VII, IX, X) and decrease Anti-thrombin III, increasing the risk of **Thromboembolism**. * **Biliary Effect:** Oestrogens increase cholesterol secretion into bile, raising the risk of **gallstones** (cholelithiasis). * **Bone:** They promote the closure of epiphyses but protect bone density by inhibiting osteoclast activity.

Question 133: Danazol is a/an:

A. Anabolic steroid
B. Androgen agonist (Correct Answer)
C. Anti-androgen
D. 5-alpha-reductase inhibitor

Explanation: ### Explanation **Correct Option: B (Androgen agonist)** Danazol is a synthetic ethisterone derivative that acts as a **weak androgen agonist**. Its primary mechanism of action involves binding to androgen, progesterone, and glucocorticoid receptors. In the context of the hypothalamic-pituitary-ovarian axis, it suppresses the mid-cycle surge of LH and FSH (gonadotropin inhibition), leading to a state of "pseudomenopause." This makes it effective in treating endometriosis and fibrocystic breast disease. Additionally, it increases the levels of C1 esterase inhibitor, making it the drug of choice for prophylaxis in hereditary angioedema. **Why other options are incorrect:** * **A. Anabolic steroid:** While Danazol has weak androgenic properties, it is not classified as a primary anabolic steroid (like Stanozolol or Oxandrolone) used for muscle wasting or weight gain. * **C. Anti-androgen:** Danazol exerts androgenic effects rather than blocking them. Examples of anti-androgens include Flutamide or Spironolactone. * **D. 5-alpha-reductase inhibitor:** These drugs (e.g., Finasteride, Dutasteride) inhibit the conversion of testosterone to dihydrotestosterone (DHT). Danazol does not interfere with this enzyme. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Prophylaxis of **Hereditary Angioedema** (increases C1 esterase inhibitor levels). * **Side Effects:** Weight gain, acne, hirsutism, and deepening of voice (due to its androgenic nature). * **Contraindication:** Pregnancy (Category X) due to the risk of virilization of a female fetus. * **Other uses:** Endometriosis, Menorrhagia, and Immune Thrombocytopenic Purpura (ITP).

Question 134: Which of the following is NOT used in the management of thyroid storm?

A. Potassium iodide
B. Reserpine (Correct Answer)
C. Propranolol
D. Calcium channel blockers

Explanation: Explanation: Thyroid storm is a life-threatening medical emergency characterized by severe thyrotoxicosis. The management focuses on four pillars: inhibiting hormone synthesis, blocking hormone release, preventing peripheral conversion of T4 to T3, and controlling sympathetic overactivity. **Why Reserpine is the Correct Answer:** Historically, **Reserpine** (and Guanethidine) were used to manage the sympathetic symptoms of thyrotoxicosis by depleting catecholamine stores. However, they are **no longer used** in modern clinical practice due to their slow onset of action and significant side effects (severe depression, sedation, and hypotension). In the context of current NEET-PG standards, they are considered obsolete for this indication. **Analysis of Other Options:** * **Potassium Iodide (Option A):** Used to inhibit the release of preformed thyroid hormones from the gland (the **Wolff-Chaikoff effect**) [2]. It is typically administered at least one hour after starting antithyroid drugs [1]. * **Propranolol (Option C):** The drug of choice for immediate symptomatic relief [3]. It controls tachycardia and tremors while also inhibiting the peripheral conversion of T4 to T3 at high doses [3]. * **Calcium Channel Blockers (Option D):** Non-dihydropyridines like **Diltiazem** are used as second-line agents for heart rate control in patients where Beta-blockers are contraindicated (e.g., severe asthma). **High-Yield Clinical Pearls for NEET-PG:** 1. **Propylthiouracil (PTU)** is preferred over Methimazole in thyroid storm because it additionally inhibits peripheral T4 to T3 conversion. 2. **Glucocorticoids (Dexamethasone/Hydrocortisone)** are used to treat potential adrenal insufficiency and further inhibit peripheral T3 conversion. 3. **Bile acid sequestrants (Cholestyramine)** can be used in refractory cases to decrease the enterohepatic circulation of thyroid hormones.

Question 135: Which of the following insulins has the longest duration of action?

A. Global zinc suspension
B. Insulin-zinc suspension
C. Neutral protamine Hagedorn (NPH) insulin
D. Protamine-zinc insulin (Correct Answer)

Explanation: **Explanation:** The duration of action of insulin preparations is primarily determined by their rate of absorption from the subcutaneous site, which is influenced by the physical state (crystalline vs. amorphous) and the addition of retarding agents like zinc or protamine. **Why Protamine-Zinc Insulin (PZI) is correct:** PZI is a **long-acting (ultralente)** insulin. It contains a high concentration of both protamine and zinc, which leads to the formation of large, poorly soluble complexes. These complexes dissociate very slowly at the injection site, resulting in a prolonged duration of action, typically exceeding **24 to 36 hours**. Among the options provided, it has the slowest onset and the longest duration. **Analysis of Incorrect Options:** * **Neutral Protamine Hagedorn (NPH):** Also known as Isophane insulin, this is an **intermediate-acting** insulin. It contains stoichiometric amounts of protamine and has a duration of approximately 12–18 hours. * **Insulin-Zinc Suspension (Lente):** This is a mixture of 70% crystalline (ultralente) and 30% amorphous (semilente) insulin. It is **intermediate-acting** with a duration of 18–24 hours. * **Global Zinc Suspension:** This is a less common term, but zinc suspensions generally fall into intermediate or long-acting categories depending on the crystal size; however, they do not exceed the duration provided by the protamine-zinc combination. **High-Yield NEET-PG Pearls:** * **Ultra-Short Acting (Rapid):** Lispro, Aspart, Glulisine (Mnemonic: **L**ispro **A**spart **G**lulisine = **LAG**). * **Longest Acting (Modern Analogues):** **Degludec** (>42 hours) is currently the longest-acting insulin analogue, followed by Glargine (U-300). * **Protamine Caution:** Protamine-containing insulins (NPH, PZI) should **never** be given intravenously; they are for subcutaneous use only. * **Glargine:** Known as "peakless" insulin because it provides a steady basal level.

Question 136: Which of the following drugs does NOT cause gynecomastia?

A. Cimetidine
B. Spironolactone
C. Pyrazinamide (Correct Answer)
D. Ketoconazole

Explanation: **Explanation:** Gynecomastia (enlargement of male breast tissue) is a high-yield side effect in pharmacology, typically caused by drugs that either decrease testosterone synthesis, block androgen receptors, or increase estrogen levels. **Why Pyrazinamide is the correct answer:** Pyrazinamide is a first-line antitubercular drug. Its primary significant metabolic side effect is **hyperuricemia** (due to inhibition of uric acid excretion), which can precipitate gout. It also carries a risk of hepatotoxicity. However, it has no known effect on the hypothalamic-pituitary-gonadal axis or steroid hormone receptors and, therefore, **does not cause gynecomastia.** **Analysis of Incorrect Options:** * **Cimetidine:** An H2-receptor blocker that causes gynecomastia via two mechanisms: it acts as a mild anti-androgen (blocking androgen receptors) and inhibits the cytochrome P450 enzymes responsible for estradiol metabolism. * **Spironolactone:** A potassium-sparing diuretic and aldosterone antagonist. It is a notorious cause of gynecomastia because it inhibits testosterone synthesis and competes with dihydrotestosterone (DHT) for androgen receptors. (Note: Eplerenone is a more selective alternative that avoids this). * **Ketoconazole:** An antifungal that inhibits the enzyme **17,20-desmolase** (and CYP17), which is essential for steroid synthesis. This leads to decreased testosterone production. **NEET-PG High-Yield Pearls:** To remember the common drugs causing gynecomastia, use the mnemonic **"DISCO"**: * **D**igoxin (estrogenic effect) * **I**soniazid (INH - though rare, it is the TB drug that *can* cause it, unlike Pyrazinamide) * **S**pironolactone * **C**imetidine * **O**estrogens / **K**etoconazole (the 'K' sound) *Other notable mentions: Finasteride, Risperidone (via hyperprolactinemia), and Marijuana.*

Question 137: Raloxifene is used in which of the following conditions?

A. Osteoporosis (Correct Answer)
B. Cervical cancer
C. Osteopetrosis
D. Fibroadenoma

Explanation: **Explanation:** **Raloxifene** is a second-generation **Selective Estrogen Receptor Modulator (SERM)**. Its therapeutic utility stems from its unique ability to act as an estrogen **agonist** in some tissues while acting as an **antagonist** in others. 1. **Why Osteoporosis is correct:** Raloxifene acts as an **estrogen agonist on bone**. It inhibits osteoclast activity and reduces bone resorption, thereby increasing bone mineral density. It is specifically FDA-approved for the prevention and treatment of **postmenopausal osteoporosis**. 2. **Why other options are incorrect:** * **Cervical cancer:** Raloxifene has no role here. It is, however, used to reduce the risk of invasive **breast cancer** due to its estrogen antagonist effect on breast tissue. * **Osteopetrosis:** This is a genetic disorder characterized by increased bone density (marble bone disease) due to defective osteoclasts. Raloxifene, which further inhibits osteoclasts, would be contraindicated or irrelevant. * **Fibroadenoma:** While Raloxifene affects breast tissue, it is not a standard treatment for benign fibroadenomas. **High-Yield Clinical Pearls for NEET-PG:** * **Tissue Specificity:** Agonist on **Bone** and **Lipids** (lowers LDL); Antagonist on **Breast** and **Endometrium**. * **Key Advantage:** Unlike Tamoxifen, Raloxifene is an antagonist at the endometrium; therefore, it **does not increase the risk of endometrial cancer**. * **Adverse Effects:** Most common are **hot flashes** and leg cramps. The most serious risk is **Venous Thromboembolism (VTE)**. * **Contraindication:** History of venous thromboembolic events or prolonged immobilization.

Question 138: Which phosphodiesterase inhibitor is used for erectile dysfunction?

A. Sildenafil (Correct Answer)
B. Amrinone
C. Milrinone
D. Tamoxifen

Explanation: **Explanation:** **Sildenafil** is the correct answer because it is a selective inhibitor of **Phosphodiesterase-5 (PDE-5)**. In the corpus cavernosum of the penis, sexual stimulation leads to the release of Nitric Oxide (NO), which activates guanylyl cyclase to produce **cyclic GMP (cGMP)**. cGMP causes smooth muscle relaxation and increased blood flow, leading to an erection. PDE-5 is the enzyme responsible for the degradation of cGMP. By inhibiting PDE-5, Sildenafil prevents the breakdown of cGMP, thereby enhancing and prolonging the erectile response. **Analysis of Incorrect Options:** * **Amrinone & Milrinone:** These are **PDE-3 inhibitors**. They increase cAMP levels in cardiac myocytes and vascular smooth muscle. They are used as inotropic agents in the short-term management of acute heart failure, not for erectile dysfunction. * **Tamoxifen:** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as an antagonist in breast tissue and is used in the treatment and prevention of breast cancer. It has no effect on phosphodiesterase enzymes. **High-Yield Clinical Pearls for NEET-PG:** * **Contraindication:** Sildenafil must **never** be co-administered with **Nitrates** (e.g., Nitroglycerin) as it can lead to life-threatening hypotension due to synergistic increases in cGMP. * **Side Effects:** Common side effects include headache, flushing, and **cyanopsia** (blue-tinted vision) due to cross-inhibition of PDE-6 in the retina. * **Other PDE-5 Inhibitors:** Tadalafil (longer half-life, "the weekend pill") and Vardenafil. * **Other Indications:** Sildenafil is also FDA-approved for the treatment of **Pulmonary Arterial Hypertension (PAH)**.

Question 139: Medical castration is effected by which of the following?

A. Diethylstilbesterol
B. LH RH analogues (Correct Answer)
C. Gossypol
D. Hanovan

Explanation: **Explanation:** **Medical castration** refers to the use of drugs to reduce serum testosterone levels to castrate levels (typically <50 ng/dL), achieving the same hormonal effect as a bilateral orchiectomy (surgical castration). **Why LH-RH Analogues are correct:** LH-RH (GnRH) analogues like **Leuprolide, Goserelin, and Nafarelin** are the mainstay for medical castration. * **Mechanism:** Initially, they cause a transient "flare" of LH and FSH. However, continuous administration leads to the **downregulation and desensitization of GnRH receptors** in the pituitary gland. * **Result:** This suppresses the secretion of LH and FSH, leading to a profound drop in testosterone production by the Leydig cells in the testes. **Analysis of Incorrect Options:** * **A. Diethylstilbesterol (DES):** A synthetic estrogen formerly used for prostate cancer. While it suppresses the hypothalamic-pituitary-gonadal axis, it is no longer the preferred method for medical castration due to significant cardiovascular toxicity and thromboembolic risks. * **C. Gossypol:** A polyphenolic compound derived from cottonseed. It is studied as a **male contraceptive** because it inhibits sperm production (spermatogenesis) and motility, but it does not achieve castrate levels of testosterone. * **D. Hanovan:** This is not a standard pharmacological agent used in endocrine therapy or medical castration. **High-Yield Clinical Pearls for NEET-PG:** * **Flare Phenomenon:** To prevent the initial testosterone surge (flare) caused by GnRH agonists, they are often co-administered with **Flutamide** (an androgen receptor antagonist) for the first few weeks of therapy. * **GnRH Antagonists:** Drugs like **Degarelix and Abarelix** achieve medical castration more rapidly than agonists without causing a testosterone flare. * **Indications:** Medical castration is primarily used in the management of **Advanced Prostate Cancer**.

Question 140: SIADH is caused by all of the following drugs except:

A. Vincristine
B. Vinblastine
C. Actinomycin D (Correct Answer)
D. Cyclophosphamide

Explanation: **Explanation:** The Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is a common paraneoplastic syndrome, but it is also a well-documented side effect of several chemotherapeutic agents. **Why Actinomycin D is the correct answer:** Actinomycin D (Dactinomycin) is an antitumor antibiotic used primarily in pediatric tumors like Wilms' tumor and Ewing sarcoma. Unlike the other options listed, it is **not** associated with the induction of SIADH. Its primary dose-limiting toxicities are bone marrow suppression and gastrointestinal mucosal damage. **Analysis of incorrect options:** * **Vincristine & Vinblastine (Vinca Alkaloids):** These are classic causes of drug-induced SIADH. They are thought to exert a direct toxic effect on the neurohypophysis or the hypothalamic-neurohypophyseal tract, leading to the unregulated release of ADH. * **Cyclophosphamide:** This alkylating agent is a high-yield cause of SIADH, particularly when administered in high doses. It enhances the effect of ADH on the renal tubules. **Clinical Note:** This is particularly dangerous because patients receiving cyclophosphamide are often aggressively hydrated to prevent hemorrhagic cystitis, increasing the risk of severe hyponatremia. **NEET-PG High-Yield Pearls:** 1. **Common Drugs causing SIADH (Mnemonic: "S-S-C-V"):** **S**SRIs (Fluoxetine), **S**ulfonylureas (Chlorpropamide), **C**arbamazepine/Cyclophosphamide, and **V**inca Alkaloids. 2. **Management:** The mainstay of treatment for drug-induced SIADH is the discontinuation of the offending agent and fluid restriction. In chronic cases, **Demeclocycline** (an ADH antagonist) or **Tolvaptan** (V2 receptor antagonist) may be used. 3. **Diagnosis:** Look for hyponatremia, low serum osmolality, and inappropriately high urine osmolality in a normovolemic patient.

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

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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