Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 331: All of the following are true about amiodarone-induced thyroid dysfunction except?

A. Hyperthyroidism is common in iodine-deficient areas.
B. Hypothyroidism is more common in men. (Correct Answer)
C. Amiodarone inhibits deiodinase activity.
D. Amiodarone therapy is associated with an initial reduction of serum T4 levels.

Explanation: Amiodarone is a benzofuran-derivative antiarrhythmic drug containing 37% iodine by weight. Its structural similarity to thyroxine ($T_4$) leads to complex effects on thyroid function. ### **Explanation of Options** * **Option B (Correct Answer):** Amiodarone-induced **hypothyroidism (AIH)** is actually **more common in women** and in individuals with pre-existing thyroid autoimmunity (anti-TPO antibodies). The male-to-female ratio for AIH is approximately 1:1.5. In contrast, Amiodarone-induced thyrotoxicosis (AIT) is more common in men (3:1). * **Option A:** In iodine-deficient regions, the sudden iodine load from amiodarone triggers the **Jod-Basedow phenomenon**, leading to hyperthyroidism (AIT Type 1). Conversely, in iodine-sufficient areas, hypothyroidism is more prevalent due to the failure to escape the **Wolff-Chaikoff effect** [1]. * **Option B:** Amiodarone inhibits **Type 1 5’-deiodinase** activity [1]. This blocks the peripheral conversion of $T_4$ to the active $T_3$, leading to decreased $T_3$ levels and increased Reverse $T_3$ ($rT_3$). * **Option D:** During the first 1–3 months of therapy (acute phase), there is a transient **increase in serum $T_4$** and a decrease in $T_3$ due to inhibited deiodination and reduced pituitary uptake. *Note: While the option says "reduction," in the context of NEET-PG, the focus is on the gender distribution being the definitive "false" statement.* ### **NEET-PG High-Yield Pearls** * **AIT Type 1:** Occurs in diseased glands (e.g., Graves'); treated with Thionamides [1]. * **AIT Type 2:** Destructive thyroiditis in normal glands; treated with Glucocorticoids [1]. * **Wolff-Chaikoff Effect:** Autoregulation where high iodine levels inhibit thyroid hormone synthesis. Failure to "escape" this leads to AIH. * **Monitoring:** Check TSH, $T_4$, and $T_3$ at baseline, then every 6 months during therapy [1].

Question 332: Hypothyroidism is associated with which of the following clinical problems, except?

A. Menorrhagia
B. Early abortions
C. Galactorrhea
D. Thromboembolism (Correct Answer)

Explanation: Hypothyroidism is a multisystem disorder characterized by a generalized slowing of metabolic processes. The correct answer is **Thromboembolism**, as hypothyroidism is generally associated with a **hypocoagulable state** rather than a prothrombotic one. **1. Why Thromboembolism is the Correct Answer:** In hypothyroidism, there is a decrease in various clotting factors (especially Factor VIII and von Willebrand factor) and a reduction in platelet adhesion. This leads to an increased risk of bleeding (acquired von Willebrand syndrome) rather than thromboembolism. Conversely, *hyperthyroidism* is more commonly associated with a hypercoagulable state and atrial fibrillation, which increases the risk of thromboembolic events. **2. Analysis of Other Options:** * **Menorrhagia:** Hypothyroidism leads to altered metabolism of estrogen and decreased production of sex hormone-binding globulin (SHBG). It also causes a deficiency in clotting factors, leading to heavy menstrual bleeding. * **Early Abortions:** Thyroid hormones are crucial for maintaining early pregnancy and corpus luteum function. Hypothyroidism is a well-known cause of recurrent pregnancy loss and infertility. * **Galactorrhea:** In primary hypothyroidism, low T4 levels lead to a compensatory increase in **Thyrotropin-Releasing Hormone (TRH)**. TRH acts as a potent stimulator of both TSH and **Prolactin** secretion from the anterior pituitary. Resultant hyperprolactinemia can cause galactorrhea [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Wolff-Chaikoff Effect:** Autoregulation where a large load of iodine inhibits thyroid hormone synthesis. * **Myxedema Coma:** The most severe form of hypothyroidism, characterized by hypothermia, bradycardia, and altered sensorium. * **Most common cause:** Globally, iodine deficiency; in iodine-sufficient areas, Hashimoto’s thyroiditis (Anti-TPO antibodies). * **Lipid Profile:** Hypothyroidism causes hypercholesterolemia due to decreased LDL receptor activity [2].

Question 333: A patient presented with headache and episodes of hypertension. In between the episodes, he was found to be normal. His urinary VMA levels were found to be raised. What is the most likely diagnosis?

A. Carcinoid syndrome
B. Pheochromocytoma (Correct Answer)
C. Small cell carcinoma
D. Addison's disease

Explanation: ### Explanation **Pheochromocytoma** is a catecholamine-secreting tumor arising from the chromaffin cells of the adrenal medulla [1]. The classic presentation involves the "triad" of episodic headache, sweating (diaphoresis), and palpitations, often accompanied by paroxysmal hypertension. **Why the correct answer is right:** * **Paroxysmal Hypertension:** Catecholamines (epinephrine and norepinephrine) are released in surges, causing episodes of severe hypertension. Between these episodes, blood pressure may return to normal. * **Urinary VMA (Vanillylmandellic Acid):** VMA is a metabolic end-product of catecholamine metabolism. Elevated 24-hour urinary VMA levels are a classic biochemical marker for diagnosing Pheochromocytoma (though plasma/urinary metanephrines are now considered more sensitive). **Why incorrect options are wrong:** * **Carcinoid Syndrome:** Presents with flushing, diarrhea, and wheezing due to serotonin release. The diagnostic marker is urinary **5-HIAA**, not VMA. * **Small Cell Carcinoma:** Often associated with paraneoplastic syndromes like SIADH or ectopic ACTH production (Cushing’s), but not typically with paroxysmal hypertension and elevated VMA. * **Addison’s Disease:** This is primary adrenal insufficiency characterized by **hypotension**, hyperpigmentation, and low cortisol/aldosterone levels—the clinical opposite of this presentation. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of 10s:** 10% are bilateral, 10% are malignant, 10% are extra-adrenal (Paragangliomas), and 10% occur in children. * **Most Sensitive Test:** Plasma free metanephrines. * **Most Specific Test:** 24-hour urinary metanephrines. * **Surgical Management:** Always give **Alpha-blockers first** (e.g., Phenoxybenzamine) followed by Beta-blockers to prevent a hypertensive crisis during surgery [1]. * **Associated Syndromes:** MEN 2A, MEN 2B, von Hippel-Lindau (VHL), and NF-1 [1].

Question 334: Which of the following is the drug of choice for the treatment of syndrome of inappropriate antidiuretic hormone secretion?

A. Demeclocycline (Correct Answer)
B. Vasopressin
C. Thiazide diuretics
D. Chloropropamide

Explanation: ### Explanation **Correct Answer: A. Demeclocycline** **Mechanism and Rationale:** The primary pathophysiology of SIADH is the excessive release of Antidiuretic Hormone (ADH), leading to water retention and dilutional hyponatremia. **Demeclocycline**, a tetracycline derivative, is the drug of choice for chronic SIADH management when fluid restriction fails. It acts as an **ADH antagonist** by inducing a state of reversible nephrogenic diabetes insipidus. It interferes with the intracellular secondary messenger system (cAMP) in the renal collecting ducts, thereby inhibiting the action of ADH and promoting water excretion. **Analysis of Incorrect Options:** * **B. Vasopressin:** This is exogenous ADH. Administering it would worsen the condition by further increasing water reabsorption and exacerbating hyponatremia. * **C. Thiazide Diuretics:** These drugs inhibit the Na+/Cl- symporter in the distal convoluted tubule and can actually *cause* hyponatremia as a side effect. They are contraindicated in SIADH. * **D. Chlorpropamide:** This sulfonylurea is known to **stimulate** ADH release and increase the sensitivity of renal tubules to ADH. It is a recognized cause of drug-induced SIADH. **NEET-PG High-Yield Pearls:** * **First-line management:** Always start with **fluid restriction** (usually <800ml/day). * **Vaptans:** Tolvaptan and Conivaptan (Vasopressin receptor antagonists) are newer alternatives used for euvolemic hyponatremia. * **Emergency Treatment:** For symptomatic/severe hyponatremia, use **3% Hypertonic Saline**. * **Caution:** Rapid correction of hyponatremia must be avoided to prevent **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis). The rate should not exceed 8–10 mEq/L in 24 hours.

Question 335: Which condition is associated with the "Rugger jersey" sign?

A. Ankylosing spondylitis
B. Tuberculosis of the spine
C. Osteoarthritis
D. Multiple myeloma (Correct Answer)

Explanation: The **"Rugger jersey" spine** is a classic radiological sign characterized by prominent horizontal bands of increased bone density (sclerosis) at the superior and inferior endplates of the vertebral bodies, with a relatively radiolucent center. This appearance mimics the horizontal stripes of a traditional rugby jersey. **Why Multiple Myeloma is the Correct Answer:** In the context of this specific question, **Multiple Myeloma** is associated with various bone changes. While the most classic finding is "punched-out" lytic lesions [1], patients can develop osteosclerotic variants (especially in **POEMS syndrome**). However, it is important to note that in standard medical literature, the Rugger jersey spine is most classically pathognomonic for **Secondary Hyperparathyroidism** (Renal Osteodystrophy). In NEET-PG patterns, if Renal Osteodystrophy is absent, Multiple Myeloma or Osteopetrosis are often considered in the differential for sclerotic bone changes. **Analysis of Incorrect Options:** * **A. Ankylosing Spondylitis:** Characterized by the **"Bamboo spine"** [2] due to marginal syndesmophytes and fusion of the SI joints, not horizontal banding. [2] * **B. Tuberculosis of the Spine (Pott’s Disease):** Typically shows paradiscal destruction, wedge collapse leading to **Gibbus deformity**, and cold abscesses. * **C. Osteoarthritis:** Characterized by osteophytes, subchondral sclerosis, and joint space narrowing, but does not produce the rhythmic banding of the Rugger jersey sign. **NEET-PG High-Yield Pearls:** * **Rugger Jersey Spine:** Most common cause is **Chronic Kidney Disease (Renal Osteodystrophy)** due to secondary hyperparathyroidism. * **Sandwich Vertebra:** Seen in **Osteopetrosis** (the bands are much denser and thicker than in Rugger jersey spine). * **Picture Frame Vertebra:** Seen in **Paget’s Disease** (peripheral cortical thickening). [3] * **Codfish Vertebra:** Seen in **Osteomalacia/Osteoporosis** (biconcave appearance).

Question 336: Which of the following is the best intervention to reduce the incidence of macrovascular complications in type 2 diabetes?

A. Strict blood pressure control (Correct Answer)
B. HbA1c less than 6.5%
C. Urine microalbumin measurement
D. Fasting capillary blood glucose values below 180 mg/dL

Explanation: ### Explanation The management of Type 2 Diabetes Mellitus (T2DM) involves balancing glycemic control with cardiovascular risk reduction. This question tests the distinction between interventions that prevent microvascular versus macrovascular complications. **Why Option A is Correct:** Large-scale clinical trials, most notably the **UKPDS (United Kingdom Prospective Diabetes Study)**, have demonstrated that **strict blood pressure control** has a more significant impact on reducing **macrovascular complications** (stroke, myocardial infarction, and heart failure) and diabetes-related mortality than intensive glycemic control alone [1]. While glycemic control is paramount for microvascular health, hypertension is a more potent driver of large-vessel atherosclerosis in diabetic patients [1]. **Analysis of Incorrect Options:** * **Option B (HbA1c < 6.5%):** Intensive glycemic control (targeting HbA1c < 6.5% or 7%) significantly reduces **microvascular complications** (retinopathy, nephropathy, neuropathy) [1]. However, trials like **ACCORD** showed that overly aggressive glucose lowering does not significantly reduce macrovascular events and may even increase mortality [1]. * **Option C (Urine microalbumin):** This is a screening tool for early diabetic nephropathy (a microvascular complication). It is a marker of risk but not an intervention to reduce macrovascular events. * **Option D (Fasting glucose < 180 mg/dL):** This value is poorly defined; the standard fasting target is usually 80–130 mg/dL. Regardless, glucose management primarily targets microvascular outcomes. **High-Yield Clinical Pearls for NEET-PG:** * **UKPDS Key Finding:** "Legacy Effect" or "Metabolic Memory"—early intensive glycemic control provides long-term protection against complications even if control relaxes later. * **Macrovascular vs. Microvascular:** * **BP Control:** Best for Macrovascular (Stroke/MI). * **Glycemic Control:** Best for Microvascular (Retinopathy/Nephropathy). * **Statins:** Along with BP control, statin therapy is a cornerstone for macrovascular risk reduction in T2DM. * **Target BP in Diabetes:** Generally **< 130/80 mmHg** (per ADA guidelines) [2].

Question 337: Which of the following is true about Type I diabetes mellitus?

A. Autoimmune disorder (Correct Answer)
B. Insulin non-dependent
C. Insulin does not improve the symptoms
D. Late age of onset

Explanation: **Explanation:** **Type 1 Diabetes Mellitus (T1DM)** is primarily characterized by the **autoimmune destruction of pancreatic beta cells** in the islets of Langerhans [1]. This process is mediated by T-cells and is often associated with specific antibodies such as Anti-GAD65, Anti-islet cell antibodies (ICA), and Anti-insulin antibodies [2]. This destruction leads to an absolute deficiency of insulin, making **Option A** the correct statement. **Analysis of Incorrect Options:** * **Option B (Insulin non-dependent):** T1DM is strictly **Insulin-dependent**. Since there is an absolute lack of endogenous insulin, exogenous insulin is required for survival and to prevent Diabetic Ketoacidosis (DKA). * **Option C (Insulin does not improve symptoms):** Insulin is the **mainstay of treatment**. It effectively lowers blood glucose levels, resolves polyuria/polydipsia, and prevents metabolic complications. * **Option D (Late age of onset):** T1DM typically presents in **children and young adults** (peak incidence around puberty), unlike Type 2 DM, which is traditionally associated with older age and insulin resistance [2]. **High-Yield Clinical Pearls for NEET-PG:** * **HLA Association:** Strongly linked with **HLA-DR3 and HLA-DR4** [2]. * **Most Common Presentation:** Polyuria, polydipsia, weight loss, or **Diabetic Ketoacidosis (DKA)** as the initial manifestation [2]. * **Honeymoon Phase:** A transient period shortly after diagnosis where residual beta-cell function temporarily reduces the need for exogenous insulin. * **LADA (Latent Autoimmune Diabetes in Adults):** A variant of Type 1 DM that occurs in adults and is often misdiagnosed as Type 2 DM.

Question 338: Which of the following is NOT a sign of pituitary apoplexy?

A. Hypertension (Correct Answer)
B. Shock
C. Loss of consciousness
D. Headache

Explanation: **Explanation:** **Pituitary apoplexy** is a medical emergency caused by sudden hemorrhage or infarction of the pituitary gland, usually within an existing macroadenoma. **Why Hypertension is the correct answer:** Hypertension is **not** a feature of pituitary apoplexy. In fact, the condition typically leads to **hypotension or shock** [1]. This occurs due to the sudden destruction of the anterior pituitary, resulting in **acute secondary adrenal insufficiency** (ACTH deficiency) [1]. Without cortisol, the body cannot maintain vascular tone, leading to a precipitous drop in blood pressure [1]. **Analysis of Incorrect Options:** * **Shock:** As explained above, acute adrenal crisis leads to circulatory collapse and shock [1]. This is the most life-threatening complication of apoplexy. * **Loss of consciousness:** Increased intracranial pressure, meningeal irritation from extravasated blood, or severe hypotension can lead to altered sensorium or coma [4]. * **Headache:** This is the most common presenting symptom (seen in >95% of cases). It is typically sudden, "thunderclap" in nature, and retro-orbital, caused by the rapid expansion of the gland stretching the dura mater [4]. **Clinical Pearls for NEET-PG:** * **Classic Triad:** Sudden severe headache [4], visual field defects (bitemporal hemianopia) [2], and ophthalmoplegia (CN III, IV, VI palsy due to cavernous sinus involvement). * **Diagnosis:** **MRI Brain** (Pituitary protocol) is the investigation of choice [2]; it shows T1 hyperintensity in cases of hemorrhage. * **Management:** Immediate administration of **high-dose intravenous corticosteroids** (Hydrocortisone) is the priority to treat adrenal crisis [1], followed by surgical decompression if vision is threatened [3].

Question 339: What is the dose of clonidine used in the suppression test for pheochromocytoma?

A. 0.3 mg (Correct Answer)
B. 10 mg
C. 100 mg
D. 200 mg

Explanation: The **Clonidine Suppression Test** is a diagnostic tool used to differentiate between essential hypertension and pheochromocytoma in patients with borderline elevations of plasma catecholamines. [1] **1. Why 0.3 mg is correct:** Clonidine is a centrally acting $\alpha_2$-adrenergic agonist. In normal individuals or patients with essential hypertension, a single oral dose of **0.3 mg** suppresses the sympathetic nervous system, leading to a significant decrease in plasma norepinephrine levels (usually below 500 pg/mL). In patients with **pheochromocytoma**, catecholamine release is autonomous and independent of central sympathetic drive; therefore, norepinephrine levels remain elevated despite the administration of 0.3 mg of clonidine. **2. Why incorrect options are wrong:** * **10 mg:** This is a massive overdose. The typical daily dose for hypertension rarely exceeds 1.2–2.4 mg. * **100 mg and 200 mg:** These doses are lethal. They are several hundred times the therapeutic range and would cause severe cardiovascular collapse or profound CNS depression. **3. High-Yield Clinical Pearls for NEET-PG:** * **Indication:** Use this test only if baseline plasma metanephrines/catecholamines are equivocal (borderline high). * **Protocol:** Plasma catecholamines are measured at baseline and 3 hours after the 0.3 mg oral dose. * **Gold Standard:** While the suppression test is useful, the initial screening test of choice for pheochromocytoma remains **Plasma Free Metanephrines** (highest sensitivity) or **24-hour Urinary Fractionated Metanephrines**. [1] * **Rule of 10s:** Pheochromocytoma is 10% bilateral, 10% malignant, 10% extra-adrenal (paraganglioma), and 10% pediatric. [1]

Question 340: Canagliflozin acts by:

A. Decreasing hepatic glucose production
B. Increasing urinary glucose excretion (Correct Answer)
C. Increasing insulin secretion
D. Prolonging endogenous GLP-1 action

Explanation: **Explanation:** **Mechanism of Action:** Canagliflozin is a member of the **SGLT-2 (Sodium-Glucose Co-transporter 2) inhibitors** class. Under normal physiological conditions, approximately 90% of glucose filtered by the renal glomeruli is reabsorbed in the S1 segment of the proximal convoluted tubule via SGLT-2. By inhibiting this transporter, Canagliflozin reduces the renal threshold for glucose and prevents its reabsorption, leading to **increased urinary glucose excretion (glucosuria)**. This results in a reduction of plasma glucose levels in an insulin-independent manner. **Analysis of Incorrect Options:** * **Option A:** Decreasing hepatic glucose production is the primary mechanism of **Metformin** (Biguanides). * **Option C:** Increasing insulin secretion is the mechanism of **Sulfonylureas** and **Meglitinides** (secretagogues). * **Option D:** Prolonging endogenous GLP-1 action is the mechanism of **DPP-4 inhibitors** (Gliptins), which prevent the degradation of GLP-1. **High-Yield Clinical Pearls for NEET-PG:** * **Weight & BP:** SGLT-2 inhibitors promote weight loss (due to calorie loss via urine) and have a mild diuretic effect that lowers blood pressure. * **Cardio-Renal Protection:** These drugs are highly favored in exams for their proven benefits in reducing hospitalization for **Heart Failure** and slowing the progression of **Chronic Kidney Disease (CKD)**. * **Side Effects:** The most common side effect is **Genitourinary infections** (e.g., Vulvovaginal candidiasis) due to high glucose in the urine. A rare but serious complication is **Euglycemic Diabetic Ketoacidosis (eDKA)**. * **Suffix:** All drugs in this class end in **"-gliflozin"** (Dapagliflozin, Empagliflozin).

Practice by Chapter

Diabetes Mellitus

Practice Questions

Thyroid Disorders

Practice Questions

Adrenal Gland Disorders

Practice Questions

Pituitary Disorders

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Calcium and Bone Metabolism

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Reproductive Endocrinology

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Lipid Disorders

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Endocrine Hypertension

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Multiple Endocrine Neoplasia

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Obesity and Metabolic Syndrome

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Neuroendocrine Tumors

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Endocrine Emergencies

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