Endocrine Pharmacology — MCQs

Endocrine Pharmacology Indian Medical PG Practice Questions and MCQs

Question 341: Which of the following is NOT an established use of lanreotide?

A. Insulinoma
B. Carcinoid syndrome
C. Glioma (Correct Answer)
D. Glucagonoma

Explanation: **Explanation:** **Lanreotide** is a synthetic long-acting analogue of **Somatostatin**. It works by binding to somatostatin receptors (primarily SSTR-2 and SSTR-5), leading to the inhibition of various endocrine and exocrine secretions, including Growth Hormone (GH), insulin, glucagon, and serotonin. 1. **Why Glioma is the correct answer:** Gliomas are primary tumors of the glial cells in the brain. While some research has explored somatostatin receptors in neuro-oncology, lanreotide has **no established clinical role** or FDA approval for the treatment of gliomas. Its primary therapeutic utility is confined to neuroendocrine tumors and acromegaly. 2. **Analysis of Incorrect Options:** * **Carcinoid Syndrome:** Lanreotide is a mainstay treatment for managing symptoms (like flushing and diarrhea) associated with carcinoid syndrome by inhibiting the release of serotonin and other vasoactive peptides. * **Insulinoma & Glucagonoma:** These are functional Pancreatic Neuroendocrine Tumors (pNETs). Lanreotide is indicated to control the hormonal hypersecretion and provide tumor growth control (anti-proliferative effect) in these conditions. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Longer half-life than natural somatostatin; available as a sustained-release formulation (Autogel). * **Indications:** Acromegaly (when surgery/radiotherapy is inadequate), Gastroenteropancreatic Neuroendocrine Tumors (GEP-NETs), and symptomatic relief of functional endocrine tumors. * **Side Effects:** Biliary sludge or **cholelithiasis** (due to inhibition of cholecystokinin and gallbladder contractility), steatorrhea, and glucose intolerance. * **Comparison:** Octreotide is the other common analogue; Lanreotide is often preferred for its longer dosing interval (once every 4 weeks).

Question 342: A 22-year-old female presents with diarrhea, palpitations, anxiety, and abdominal pain, reporting weight loss. She mentions taking an unknown medication prescribed to someone else. Which of the following drugs is most likely responsible for her presentation?

A. Propylthiouracil (PTU)
B. Iodide
C. Methimazole
D. Levothyroxine (Correct Answer)

Explanation: ### **Explanation** **Correct Option: D. Levothyroxine** The patient is presenting with classic signs of **thyrotoxicosis** (hyperthyroidism): palpitations, anxiety, weight loss, and diarrhea. The history of taking an "unknown medication prescribed to someone else" points toward **Factitious Thyrotoxicosis** (exogenous ingestion of thyroid hormone). Levothyroxine (T4) is a synthetic thyroid hormone used for hypothyroidism; when taken by a euthyroid individual, it induces a hypermetabolic state mimicking Graves' disease, but notably without goiter or exophthalmos. **Why Incorrect Options are Wrong:** * **A & C (Propylthiouracil & Methimazole):** These are **anti-thyroid drugs (Thionamides)**. They inhibit thyroid hormone synthesis by blocking thyroid peroxidase. Overdose or misuse of these drugs would lead to **hypothyroidism** (bradycardia, weight gain, constipation), the exact opposite of this patient's presentation. * **B (Iodide):** High doses of Iodide (Lugol’s iodine) generally cause a transient inhibition of thyroid hormone release (the **Wolff-Chaikoff effect**). While it can rarely cause hyperthyroidism in patients with underlying nodules (Jod-Basedow phenomenon), it is not a common medication "prescribed to someone else" that would typically cause this acute presentation in a young female. **NEET-PG High-Yield Pearls:** * **Factitious Thyrotoxicosis:** Characterized by high T4/T3 levels, low TSH, and **suppressed (low) serum thyroglobulin** levels. * **Radioactive Iodine Uptake (RAIU):** In exogenous ingestion (Levothyroxine), the RAIU will be **low/absent** because the thyroid gland is suppressed. * **Propylthiouracil (PTU):** Preferred in the **1st trimester** of pregnancy and thyroid storm (inhibits peripheral conversion of T4 to T3). * **Methimazole:** Preferred in the 2nd and 3rd trimesters; associated with **Aplasia Cutis** if used in the 1st trimester.

Question 343: Long-term steroid therapy can lead to suppression of the hypothalamic-pituitary-adrenal axis. This can be overcome by using alternate-day therapy with corticosteroids. Which of the following steroids are unsuitable for alternate-day therapy for this purpose?

A. Cortisol
B. Prednisolone
C. Betamethasone (Correct Answer)
D. Hydrocortisone

Explanation: **Explanation:** The goal of **alternate-day therapy (ADT)** is to provide the anti-inflammatory benefits of corticosteroids while allowing the Hypothalamic-Pituitary-Adrenal (HPA) axis to recover on the "off" day. To achieve this, a steroid must have a **short-to-intermediate duration of action**. **1. Why Betamethasone is the correct answer:** Betamethasone (and Dexamethasone) are **long-acting glucocorticoids** with a biological half-life exceeding **36–72 hours**. Because their effects last significantly longer than 24 hours, they continue to suppress the HPA axis even on the "off" day. This prevents the pituitary from secreting ACTH, defeating the purpose of ADT. Therefore, long-acting steroids are unsuitable for this regimen. **2. Why the other options are incorrect:** * **Cortisol & Hydrocortisone (Option A & D):** These are **short-acting** steroids (8–12 hours). While they allow HPA recovery, they are often too short-lived to maintain adequate disease control for a full 48-hour cycle in ADT. * **Prednisolone (Option B):** This is an **intermediate-acting** steroid (18–36 hours). It is the **drug of choice** for ADT because its anti-inflammatory effect lasts long enough to control symptoms, but its suppressive effect on the HPA axis wears off in time for the "off" day recovery. **High-Yield NEET-PG Pearls:** * **Ideal ADT Agent:** Prednisolone, Methylprednisolone, or Triamcinolone. * **HPA Suppression Risk:** Highest with long-acting steroids (Betamethasone) and those with high mineralocorticoid activity if used chronically. * **Steroid Potency:** Betamethasone and Dexamethasone are the most potent (25–30 times more than Hydrocortisone) and have zero mineralocorticoid activity. * **Withdrawal:** Long-term therapy (>2 weeks) should never be stopped abruptly to avoid acute adrenal insufficiency (Addisonian crisis).

Question 344: All of the following therapeutic uses of corticosteroids are appropriate except:

A. Beclomethasone in bronchial asthma
B. Cortisone for Cushing's syndrome (Correct Answer)
C. Prednisolone for Rheumatoid arthritis
D. Dexamethasone for reducing intracranial pressure

Explanation: ### Explanation The correct answer is **B. Cortisone for Cushing's syndrome.** **1. Why Option B is Correct (The Concept):** Cushing’s syndrome is characterized by **excessive endogenous cortisol production** (hypercortisolism) [3]. Administering Cortisone, a synthetic glucocorticoid, would exacerbate the condition by further increasing corticosteroid levels. The treatment goal for Cushing’s syndrome is to reduce cortisol levels (via surgery or steroidogenesis inhibitors like Ketoconazole), not to supplement them. Corticosteroids are used for **replacement therapy** in adrenal insufficiency (Addison’s disease), which is the physiological opposite of Cushing’s syndrome [5]. **2. Analysis of Incorrect Options:** * **A. Beclomethasone in bronchial asthma:** This is an appropriate use. Inhaled corticosteroids (ICS) like Beclomethasone are the first-line maintenance therapy for chronic asthma due to their potent local anti-inflammatory effects [1]. * **C. Prednisolone for Rheumatoid arthritis:** This is appropriate. Low-dose oral Prednisolone is used as "bridge therapy" to provide symptomatic relief while waiting for Disease-Modifying Anti-Rheumatic Drugs (DMARDs) to take effect [1]. * **D. Dexamethasone for reducing intracranial pressure:** This is appropriate. Dexamethasone is the drug of choice for reducing vasogenic cerebral edema (e.g., associated with brain tumors) because it has high potency and minimal mineralocorticoid (salt-retaining) activity [2]. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice (DOC) for Cerebral Edema:** Dexamethasone. * **DOC for Replacement in Addison’s:** Hydrocortisone (due to balanced glucocorticoid and mineralocorticoid activity) [5]. * **Fetal Lung Maturity:** Betamethasone or Dexamethasone are used in preterm labor because they cross the placenta and have minimal protein binding. * **Side Effects:** Long-term use of corticosteroids can actually *cause* **Iatrogenic Cushing’s Syndrome**, characterized by moon facies, buffalo hump, and truncal obesity [4].

Question 345: Which of the following drugs is contraindicated in liver disease?

A. Sitagliptin
B. Saxagliptin
C. Vildagliptin (Correct Answer)
D. Alogliptin

Explanation: **Explanation:** The correct answer is **Vildagliptin**. **Why Vildagliptin is the correct answer:** Vildagliptin is unique among the Dipeptidyl Peptidase-4 (DPP-4) inhibitors because it has been associated with a risk of **hepatic dysfunction** and elevations in serum transaminases (ALT/AST). Due to this potential for hepatotoxicity, it is **contraindicated** in patients with pre-existing hepatic impairment, including those with ALT or AST levels >3 times the upper limit of normal (ULN) prior to treatment. Clinical guidelines recommend monitoring Liver Function Tests (LFTs) at three-month intervals during the first year of therapy with Vildagliptin. **Analysis of Incorrect Options:** * **Sitagliptin:** Primarily excreted unchanged by the kidneys. It does not require dose adjustment in mild-to-moderate hepatic impairment and is not contraindicated in liver disease. * **Saxagliptin:** Metabolized by the liver (CYP3A4/5), but it is considered safe for use in patients with hepatic impairment. Dose adjustments are typically required for renal impairment, not liver disease. * **Alogliptin:** Primarily excreted renally. No dose adjustment is necessary for patients with hepatic impairment, and it does not carry the same hepatotoxicity warnings as Vildagliptin. **High-Yield Clinical Pearls for NEET-PG:** * **Renal Adjustment:** All DPP-4 inhibitors except **Linagliptin** require dose adjustment in renal failure. Linagliptin is primarily excreted via the bile/feces, making it the drug of choice for diabetic patients with CKD. * **Heart Failure Warning:** Saxagliptin and Alogliptin have been linked to an increased risk of hospitalization for heart failure. * **Weight Neutrality:** Unlike Sulfonylureas or Insulin, DPP-4 inhibitors are weight-neutral and have a low risk of hypoglycemia. * **Adverse Effect:** Nasopharyngitis is the most common side effect reported with this class.

Question 346: Medical adrenalectomy is achieved with which of the following medications?

A. Aminoglutethimide (Correct Answer)
B. Methotrexate
C. Melphalan
D. Flutamide

Explanation: **Explanation:** **Medical adrenalectomy** refers to the pharmacological inhibition of adrenal steroid synthesis, effectively mimicking a surgical adrenalectomy. **Correct Option: A. Aminoglutethimide** Aminoglutethimide is the drug of choice for medical adrenalectomy. It acts by inhibiting the enzyme **Desmolase** (CYP11A1), which converts cholesterol to pregnenolone. This is the "rate-limiting step" in the synthesis of all adrenal steroids (glucocorticoids, mineralocorticoids, and androgens). It was historically used in the treatment of Cushing’s syndrome and hormone-dependent breast cancer. **Why the other options are incorrect:** * **B. Methotrexate:** A folate antagonist (inhibits dihydrofolate reductase) used as a disease-modifying antirheumatic drug (DMARD) and in cancer chemotherapy. * **C. Melphalan:** An alkylating agent (nitrogen mustard derivative) primarily used in the treatment of multiple myeloma. * **D. Flutamide:** A non-steroidal competitive antagonist at androgen receptors, used primarily in the management of prostate cancer, not for inhibiting adrenal steroid synthesis. **High-Yield Clinical Pearls for NEET-PG:** * **Other Adrenal Steroid Inhibitors:** * **Ketoconazole:** Inhibits 17α-hydroxylase and 11β-hydroxylase; it is the most commonly used drug for Cushing’s syndrome today. * **Metyrapone:** Specifically inhibits **11β-hydroxylase**, blocking cortisol synthesis (used in diagnostic testing of the HPA axis). * **Mitotane:** An adrenolytic drug that causes selective destruction of adrenocortical cells (used in adrenal carcinoma). * **Aminoglutethimide** also inhibits the **Aromatase** enzyme, preventing the peripheral conversion of androgens to estrogens.

Question 347: What is the drug of choice for lithium-induced diabetes insipidus?

A. Conivaptan
B. Amiloride (Correct Answer)
C. Indapamide
D. Vasopressin

Explanation: **Explanation:** **Mechanism of the Correct Answer (Amiloride):** Lithium-induced Nephrogenic Diabetes Insipidus (NDI) occurs because lithium enters the principal cells of the collecting duct through **ENaC (Epithelial Sodium Channels)**. Once inside, lithium inhibits adenylate cyclase, interfering with ADH-mediated water reabsorption. **Amiloride** is the drug of choice because it is a potassium-sparing diuretic that **blocks ENaC**. By blocking these channels, amiloride prevents lithium from entering the tubular cells, thereby reversing the interference with ADH and restoring the kidney's concentrating ability. **Analysis of Incorrect Options:** * **Conivaptan:** This is a vasopressin receptor antagonist (Vaptan). It is used to treat SIADH (hyponatremia) by promoting water excretion; it would worsen the polyuria in diabetes insipidus. * **Indapamide:** While Thiazide-like diuretics (and Thiazides) are used to treat other forms of NDI by inducing mild volume depletion, they are not the specific treatment for lithium-induced cases because they do not address the lithium entry mechanism. * **Vasopressin:** In NDI, the kidneys are resistant to ADH. Therefore, administering exogenous vasopressin (or Desmopressin) will not improve the condition. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Central DI:** Desmopressin (dDAVP). * **Drug of Choice for General NDI:** Thiazides (e.g., Hydrochlorothiazide). * **Lithium Toxicity:** Lithium has a narrow therapeutic index (0.6–1.2 mEq/L). Apart from NDI, it commonly causes hypothyroidism and Ebstein's anomaly (teratogenicity). * **Paradoxical Effect:** Thiazides treat NDI by causing proximal tubule sodium/water reabsorption, reducing the volume delivered to the distal nephron.

Question 348: All of the following are true about sitagliptin EXCEPT:

A. It is always given with insulin. (Correct Answer)
B. It preferentially reduces postprandial blood sugar.
C. It has fewer side effects compared to other antidiabetic agents.
D. It lowers HbA1c.

Explanation: ### Explanation **Sitagliptin** is a competitive, reversible inhibitor of the enzyme **Dipeptidyl Peptidase-4 (DPP-4)**. This enzyme is responsible for the degradation of incretin hormones like GLP-1 and GIP. By inhibiting DPP-4, sitagliptin increases the levels of active incretins, which stimulate insulin release and inhibit glucagon secretion in a glucose-dependent manner. #### Why Option A is the Correct Answer (The False Statement) Sitagliptin is primarily used as **monotherapy** or in combination with other oral hypoglycemic agents (like Metformin or Pioglitazone) for Type 2 Diabetes Mellitus (T2DM). It is **not** always given with insulin; in fact, it is often used to delay the need for insulin therapy. Furthermore, it is not indicated for Type 1 Diabetes, where insulin is mandatory. #### Analysis of Other Options: * **Option B:** Incretins are secreted in response to food intake. Therefore, DPP-4 inhibitors primarily enhance the insulin response to meals, making them highly effective at reducing **postprandial blood sugar (PPBS)** with a minimal risk of hypoglycemia. * **Option C:** Sitagliptin is generally **weight-neutral** and has a low risk of hypoglycemia (unlike sulfonylureas) and no risk of edema or bone loss (unlike TZDs). Common side effects are mild, such as nasopharyngitis or upper respiratory tract infections. * **Option D:** Clinical trials consistently show that sitagliptin effectively lowers **HbA1c** by approximately 0.5–0.8% when used as monotherapy or in combination. #### NEET-PG High-Yield Pearls: * **Mechanism:** Glucose-dependent insulin secretion (low risk of hypoglycemia). * **Weight Effect:** Weight neutral (unlike GLP-1 agonists which cause weight loss). * **Renal Adjustment:** Requires dose adjustment in renal failure (except **Linagliptin**, which is primarily excreted via bile). * **Rare Serious Side Effect:** Acute pancreatitis (monitor for persistent severe abdominal pain).

Question 349: Which of the following statements regarding Voglibose is FALSE?

A. It acts by inhibiting the enzyme alpha-glucosidase.
B. It reduces post-prandial hyperglycemia.
C. It decreases the progression of impaired glucose tolerance to overt diabetes mellitus.
D. It can cause hypoglycemia. (Correct Answer)

Explanation: ### Explanation **Voglibose** belongs to the class of **Alpha-glucosidase inhibitors (AGIs)**. The correct answer is **D** because AGIs, when used as monotherapy, **do not cause hypoglycemia**. #### Why Option D is the Correct Answer (The False Statement) Voglibose works by delaying the digestion and absorption of carbohydrates in the small intestine. It does not stimulate insulin secretion (it is not a secretagogue). Since it only slows down glucose entry into the blood rather than forcing glucose levels down, it does not cause hypoglycemia. * *Note:* Hypoglycemia can occur only if Voglibose is combined with insulin or sulfonylureas. In such cases, the hypoglycemia must be treated with **pure glucose (dextrose)**, not sucrose (cane sugar), because Voglibose blocks the breakdown of sucrose. #### Why the Other Options are Incorrect (True Statements) * **Option A:** Voglibose competitively inhibits the enzyme **alpha-glucosidase** (e.g., maltase, sucrase) at the brush border of the small intestine, preventing the breakdown of complex carbohydrates into absorbable monosaccharides. * **Option B:** By delaying carbohydrate absorption, it specifically flattens the post-prandial glucose peak, making it highly effective for **post-prandial hyperglycemia**. * **Option C:** Large clinical trials (like the STOP-NIDDM trial for acarbose and similar studies for voglibose) have proven that AGIs significantly reduce the risk of progression from **Impaired Glucose Tolerance (IGT)** to Type 2 Diabetes. #### High-Yield NEET-PG Pearls * **Mechanism:** Competitive inhibition of intestinal $\alpha$-glucosidase. * **Side Effects:** Primarily GI-related—flatulence, bloating, and diarrhea (due to fermentation of undigested carbohydrates by colonic bacteria). * **Contraindications:** Inflammatory Bowel Disease (IBD), intestinal obstruction, or chronic intestinal diseases. * **Comparison:** Voglibose is more potent and has fewer GI side effects compared to Acarbose.

Question 350: Which of the following is NOT an adverse effect of excessive mineralocorticoid action?

A. Sodium and water retention
B. Acidosis (Correct Answer)
C. Aggravation of CHF associated myocardial fibrosis
D. Rise in blood pressure

Explanation: Mineralocorticoids (primarily **Aldosterone**) act on the mineralocorticoid receptors in the principal cells and intercalated cells of the late distal tubule and collecting duct. **Why Acidosis is the Correct Answer:** Excessive mineralocorticoid action leads to **Alkalosis**, not acidosis. Aldosterone stimulates the secretion of Hydrogen ions ($H^+$) into the tubular lumen via $H^+$-ATPase pumps in the alpha-intercalated cells. Increased loss of $H^+$ in the urine results in **Metabolic Alkalosis**. Therefore, acidosis is the incorrect physiological effect. **Explanation of Incorrect Options:** * **A. Sodium and water retention:** Aldosterone increases the expression of ENaC (Epithelial Sodium Channels) in the principal cells, promoting $Na^+$ reabsorption. Water follows osmotically, leading to volume expansion. * **D. Rise in blood pressure:** Chronic sodium and water retention, coupled with increased peripheral vascular resistance, leads to secondary hypertension. * **C. Aggravation of CHF associated myocardial fibrosis:** Beyond electrolyte balance, aldosterone has "non-genomic" effects. It promotes fibroblast proliferation and collagen deposition in the heart. This is why Mineralocorticoid Receptor Antagonists (MRAs) like **Spironolactone** and **Eplerenone** are mortality-benefit drugs in Heart Failure. **High-Yield NEET-PG Pearls:** * **Conn’s Syndrome:** Primary hyperaldosteronism characterized by the triad of **Hypertension, Hypokalemia, and Metabolic Alkalosis.** * **Escape Phenomenon:** In primary hyperaldosteronism, edema is usually absent because the body "escapes" the sodium-retaining effects via ANP (Atrial Natriuretic Peptide) release. * **Drug of Choice:** Spironolactone is the drug of choice for hepatic cirrhosis with ascites and Conn’s syndrome.

Practice by Chapter

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