Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 311: Which of the following is NOT a risk factor for the development of diabetes mellitus?

A. Sedentary lifestyle
B. High intake of vitamin A (Correct Answer)
C. Excessive intake of alcohol
D. Protein-energy malnutrition in infancy

Explanation: ### Explanation The development of Diabetes Mellitus (DM) is a multifactorial process involving genetic predisposition and environmental triggers [1]. **Why "High intake of Vitamin A" is the correct answer:** There is no established clinical evidence linking high Vitamin A intake to the pathogenesis of diabetes. While some studies suggest that Vitamin A derivatives (retinoids) play a role in pancreatic beta-cell function, excessive intake is associated with hypervitaminosis A (causing bone pain, hepatotoxicity, and skin changes) rather than glucose intolerance or insulin resistance. **Analysis of other options:** * **Sedentary Lifestyle:** This is a primary risk factor for Type 2 DM. Lack of physical activity leads to decreased insulin sensitivity in skeletal muscles and promotes visceral obesity, which further worsens insulin resistance [3]. * **Excessive Intake of Alcohol:** Chronic alcohol consumption can lead to chronic pancreatitis, resulting in "Pancreatogenic Diabetes" (Type 3c DM) due to the destruction of islet cells [2]. It also contributes to obesity and hepatic insulin resistance. * **Protein-Energy Malnutrition (PEM) in Infancy:** According to the **Barker Hypothesis** (Fetal Origins of Adult Disease), malnutrition during critical periods of development (in utero or infancy) leads to permanent changes in metabolism and reduced beta-cell mass. This increases the risk of Type 2 DM and metabolic syndrome in adulthood. **NEET-PG High-Yield Pearls:** * **Type 3c DM:** Refers to diabetes secondary to pancreatic diseases (e.g., chronic pancreatitis, cystic fibrosis) [2]. * **MODY (Maturity Onset Diabetes of the Young):** Autosomal dominant inheritance; **MODY 3 (HNF-1alfa)** is the most common type globally, while **MODY 2 (Glucokinase mutation)** is also frequently tested [4]. * **Metabolic Syndrome (Reaven's Syndrome):** A constellation of hypertension, dyslipidemia, central obesity, and insulin resistance—all major precursors to DM.

Question 312: All of the following are causes of hypercalcemia except?

A. Sarcoidosis
B. Bronchogenic carcinoma
C. Hypothyroidism (Correct Answer)
D. Lithium toxicity

Explanation: Hypercalcemia is primarily driven by increased bone resorption, excessive gastrointestinal absorption, or decreased renal excretion of calcium. **Why Hypothyroidism is the Correct Answer:** **Hypothyroidism** is typically associated with normal calcium levels or, in some cases, a slight decrease in bone turnover. In contrast, **Hyperthyroidism** (thyrotoxicosis) is a well-known cause of hypercalcemia because excess thyroid hormone (T3/T4) directly stimulates osteoclastic bone resorption [1]. Therefore, hypothyroidism does not cause hypercalcemia. **Analysis of Other Options:** * **Sarcoidosis:** This is a granulomatous disease where macrophages in the granulomas express the enzyme **1-alpha-hydroxylase**. This converts Vitamin D into its active form (1,25-dihydroxyvitamin D), leading to increased intestinal calcium absorption and hypercalcemia [1], [3]. * **Bronchogenic Carcinoma:** Specifically, **Squamous Cell Carcinoma** of the lung is a classic cause of Humoral Hypercalcemia of Malignancy (HHM) via the secretion of **PTH-related protein (PTHrP)**, which mimics PTH action on bones and kidneys [1], [2]. * **Lithium Toxicity:** Lithium shifts the set-point of the calcium-sensing receptor (CaSR) in the parathyroid glands, requiring higher calcium levels to suppress PTH secretion [2]. This results in hyperparathyroidism and subsequent hypercalcemia [1]. **NEET-PG High-Yield Pearls:** 1. **Most common cause** of hypercalcemia in outpatients is Primary Hyperparathyroidism; in hospitalized patients, it is Malignancy [1]. 2. **Milk-Alkali Syndrome:** A triad of hypercalcemia, metabolic alkalosis, and renal failure due to excessive ingestion of calcium and absorbable alkali [1]. 3. **Thiazide Diuretics** can cause hypercalcemia (by increasing renal calcium reabsorption), whereas **Loop Diuretics** (Furosemide) are used to treat it (by promoting calciuresis) [1].

Question 313: Hyponatremia with isovolemia is seen in which condition?

A. Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion (Correct Answer)
B. Conn's syndrome
C. Cushing's syndrome
D. Furosemide therapy

Explanation: **Explanation:** Hyponatremia is clinically classified based on the patient's volume status: Hypovolemic, Euvolemic (Isovolemic), or Hypervolemic [1]. **1. Why SIADH is Correct:** In **SIADH**, there is excessive release of Antidiuretic Hormone (ADH) despite normal plasma osmolality. This leads to water reabsorption in the collecting ducts, causing water retention and dilutional hyponatremia [1]. While water is retained, the body compensates by increasing urinary sodium excretion (natriuresis) to maintain near-normal extracellular fluid volume. Therefore, patients appear clinically **euvolemic/isovolemic** (no edema, no signs of dehydration) [1]. **2. Why the other options are incorrect:** * **Conn’s Syndrome (Primary Hyperaldosteronism):** Characterized by excess aldosterone, leading to sodium retention and potassium depletion. This typically results in **hypernatremia** and hypertension, not hyponatremia. * **Cushing’s Syndrome:** Excess cortisol has mineralocorticoid effects, leading to sodium and water retention. Similar to Conn’s, it is more likely to cause **hypernatremia** and hypertension. * **Furosemide Therapy:** This loop diuretic causes loss of both sodium and water. It typically results in **hypovolemic hyponatremia** due to significant fluid depletion [1]. **Clinical Pearls for NEET-PG:** * **Causes of Euvolemic Hyponatremia (Mnemonic: RATS):** **R**enal tubular acidosis, **A**ddison’s disease (secondary), **T**hyroid deficiency (Hypothyroidism), **S**IADH [1]. * **SIADH Diagnosis:** Low serum osmolality (<275 mOsm/kg), inappropriately high urine osmolality (>100 mOsm/kg), and high urine sodium (>40 mEq/L). * **Treatment Tip:** The mainstay of treatment for SIADH is **fluid restriction** [1]. For symptomatic cases, Vaptans (ADH antagonists) or hypertonic saline may be used.

Question 314: Hypertension is seen in all of the following conditions except?

A. Adrenal tumors
B. Phaeochromocytoma
C. Conn's syndrome
D. None of the above (Correct Answer)

Explanation: **Explanation:** The correct answer is **None of the above** because all three conditions listed (Adrenal tumors, Phaeochromocytoma, and Conn’s syndrome) are classic causes of **secondary hypertension**. In these cases, hypertension is mediated by the overproduction of specific hormones from the adrenal gland. * **Adrenal Tumors (Option A):** This is a broad category. Specifically, tumors of the adrenal cortex causing **Cushing’s Syndrome** (excess cortisol) lead to hypertension via mineralocorticoid effects and increased sensitivity to catecholamines. * **Phaeochromocytoma (Option B):** This is a tumor of the adrenal medulla (chromaffin cells) that secretes excessive **catecholamines** (epinephrine and norepinephrine). It typically presents with the classic triad of episodic headache, sweating, and palpitations, accompanied by sustained or paroxysmal hypertension. * **Conn’s Syndrome (Option C):** Also known as **Primary Hyperaldosteronism**, it is usually caused by an aldosterone-secreting adrenal adenoma. Excess aldosterone leads to sodium and water retention and potassium excretion, resulting in hypertension and hypokalemia. **Clinical Pearls for NEET-PG:** 1. **Screening:** Always suspect secondary hypertension in patients with early-onset HTN (<30 years), resistant HTN, or HTN with spontaneous hypokalemia. 2. **Conn’s Syndrome:** Characterized by a **high Aldosterone-to-Renin Ratio (ARR)**. 3. **Phaeochromocytoma:** Follows the "Rule of 10s" (10% bilateral, 10% malignant, 10% extra-adrenal). The best initial screening test is 24-hour urinary fractionated metanephrines or plasma free metanephrines. 4. **Cushing’s:** Hypertension is present in approximately 75-80% of patients with Cushing’s syndrome.

Question 315: What is the most reliable test in the diagnosis of pheochromocytoma?

A. 24-hour urinary metanephrine (Correct Answer)
B. Urinary catecholamines
C. Plasma catecholamines
D. Basal plasma catecholamines

Explanation: ### Explanation **Pheochromocytoma** is a catecholamine-secreting tumor derived from chromaffin cells. Understanding the metabolism of these hormones is key to selecting the right diagnostic test. **Why 24-hour urinary metanephrine is the correct answer:** Catecholamines (epinephrine and norepinephrine) are secreted **episodically** by the tumor. Therefore, a single "snapshot" measurement of plasma catecholamines may result in a false negative if the blood is drawn between secretory bursts. In contrast, **metanephrines** (metabolites of catecholamines) are produced continuously by the tumor itself via the enzyme catechol-O-methyltransferase (COMT). A **24-hour urinary collection** provides a cumulative measure of hormone production over a full day, offering high sensitivity (approx. 98%) and making it the most reliable biochemical screen. **Analysis of incorrect options:** * **Urinary catecholamines (B):** While useful, these are less sensitive than metanephrines because catecholamines have a shorter half-life and are subject to fluctuating secretion levels. * **Plasma catecholamines (C & D):** These are highly sensitive to stress, pain, and posture (sympathetic activation). A single "basal" or random sample often yields false positives due to the stress of venipuncture or false negatives due to episodic secretion. **NEET-PG High-Yield Pearls:** * **Best Initial Screening Test:** 24-hour urinary fractionated metanephrines and creatinine (to ensure adequacy of collection). * **Alternative Screen:** Plasma free metanephrines (high sensitivity, but higher false-positive rate; preferred in high-risk cases like MEN2 or VHL). * **Rule of 10s:** 10% bilateral, 10% malignant, 10% extra-adrenal (paragangliomas), 10% pediatric, and 10% familial. * **Localization:** Once biochemical diagnosis is confirmed, perform **CT or MRI** of the abdomen [1]. If negative, consider **123I-MIBG scan** [1]. * **Pre-op Management:** Always start **Alpha-blockers** (e.g., Phenoxybenzamine) *before* Beta-blockers to avoid a hypertensive crisis [1].

Question 316: A 36-year-old man presents with lethargy, weakness, and confusion. His serum sodium and serum osmolality are markedly decreased, while urine osmolality is increased. These findings are most likely related to which of the following?

A. Bronchogenic carcinoma
B. Thymoma
C. Small cell carcinoma of the lung (Correct Answer)
D. Renal cell carcinoma

Explanation: **Explanation:** The clinical presentation of lethargy, confusion, and laboratory findings of **hyponatremia** (low serum sodium), **low serum osmolality**, and **concentrated urine** (high urine osmolality) is a classic description of the **Syndrome of Inappropriate Antidiuretic Hormone (SIADH)** [1]. **Why Small Cell Carcinoma of the Lung (SCLC) is Correct:** SCLC is the most common malignancy associated with SIADH [3], [4]. It is a neuroendocrine tumor that frequently exhibits **paraneoplastic syndromes** by ectopically secreting ADH (Arginine Vasopressin) [3]. Excess ADH causes water reabsorption in the renal collecting ducts via V2 receptors and aquaporin channels, leading to dilutional hyponatremia and inappropriately concentrated urine despite low plasma osmolality [2]. **Analysis of Incorrect Options:** * **Bronchogenic Carcinoma (Option A):** While this is a broad term, it usually refers to Non-Small Cell Lung Cancer (NSCLC). Squamous cell carcinoma is classically associated with hypercalcemia (PTHrP), not SIADH [3]. * **Thymoma (Option B):** Thymomas are most commonly associated with Myasthenia Gravis, Pure Red Cell Aplasia, and Hypogammaglobulinemia (Good Syndrome). * **Renal Cell Carcinoma (Option D):** RCC is known for paraneoplastic syndromes like erythrocytosis (EPO production), hypercalcemia (PTHrP), and Stauffer syndrome, but it is not a classic cause of SIADH [3]. **High-Yield Clinical Pearls for NEET-PG:** * **SIADH Criteria:** Euvolemic hyponatremia, Urine Osmolality >100 mOsm/kg, and Urine Sodium >40 mEq/L [1]. * **Drug Causes:** Carbamazepine, Cyclophosphamide, and SSRIs are frequent triggers. * **Management:** Fluid restriction is the first-line treatment. For severe/symptomatic hyponatremia, use 3% hypertonic saline. * **Caution:** Rapid correction of hyponatremia can lead to **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis).

Question 317: What is the test of choice for diagnosing Cushing's syndrome?

A. High dose Dexamethasone suppression test
B. Overnight low dose Dexamethasone suppression test (Correct Answer)
C. Corticotropin releasing hormone test
D. Insulin tolerance test

Explanation: To diagnose Cushing’s syndrome, clinicians must follow a two-step process: **Screening** (to confirm hypercortisolism) and **Localization** (to find the source) [1]. ### Why Option B is Correct The **Overnight Low-Dose Dexamethasone Suppression Test (ONDST)** is a primary screening test. In healthy individuals, 1 mg of dexamethasone at 11 PM suppresses ACTH, leading to a morning cortisol level of **<1.8 µg/dL** [1]. Patients with Cushing’s syndrome lack this negative feedback mechanism and fail to suppress cortisol. Other valid screening tests include 24-hour urinary free cortisol and late-night salivary cortisol [1]. ### Why Other Options are Incorrect * **Option A (High-Dose DST):** This is a **localization test**, not a screening test. It is used to differentiate between Pituitary Cushing’s (which suppresses by >50%) and Ectopic ACTH production (which does not suppress). * **Option B (CRH Test):** This is used for differential diagnosis (localization) after hypercortisolism is confirmed, helping distinguish between Cushing’s disease and ectopic sources. * **Option D (Insulin Tolerance Test):** While once a gold standard for assessing the HPA axis, it is rarely used for Cushing's diagnosis due to safety risks (hypoglycemia) and is more relevant for diagnosing Growth Hormone deficiency or adrenal insufficiency. ### NEET-PG High-Yield Pearls * **Best Initial Screening Test:** ONDST or Late-night salivary cortisol [1]. * **Gold Standard for Localization:** Inferior Petrosal Sinus Sampling (IPSS) is the most accurate way to confirm a pituitary source versus an ectopic source. * **Pseudo-Cushing’s:** Conditions like depression, alcoholism, and obesity can cause false positives in screening tests. * **Drug Interference:** Phenytoin and Rifampin increase dexamethasone metabolism, potentially causing false-positive ONDST results.

Question 318: What is the cause of polyuria?

A. Hyperglycemia (Correct Answer)
B. Hypoglycemia
C. Decreased fluid intake
D. Hypocalcemia

Explanation: **Explanation:** The correct answer is **Hyperglycemia**. **Mechanism of Polyuria in Hyperglycemia:** Polyuria in hyperglycemia occurs due to **osmotic diuresis** [3]. When blood glucose levels exceed the renal threshold (approximately 180 mg/dL), the proximal convoluted tubules cannot reabsorb the excess glucose. This glucose remains in the renal tubules, acting as an osmotically active particle that holds water within the lumen, preventing its reabsorption [2]. This results in an increased volume of urine output. **Analysis of Incorrect Options:** * **B. Hypoglycemia:** Low blood sugar does not affect renal osmotic pressure and typically presents with autonomic symptoms (sweating, tremors) rather than polyuria. * **C. Decreased fluid intake:** This leads to dehydration, triggering the release of Antidiuretic Hormone (ADH) [1], which causes the kidneys to conserve water, resulting in **oliguria** (decreased urine output) [4], not polyuria. * **D. Hypocalcemia:** While **Hypercalcemia** is a known cause of polyuria (by inducing nephrogenic diabetes insipidus and interfering with ADH action), hypocalcemia typically causes neuromuscular irritability (tetany) and does not cause polyuria. **NEET-PG High-Yield Pearls:** * **Common causes of Polyuria:** Diabetes Mellitus (osmotic diuresis), Diabetes Insipidus (deficiency or resistance to ADH), Hypercalcemia, and Hypokalemia. * **Renal Threshold for Glucose:** ~180 mg/dL. * **Definition of Polyuria:** Urine output >3 L/day in adults. * **Differential Diagnosis:** Always differentiate between water diuresis (low urine osmolality, e.g., DI) and solute diuresis (high urine osmolality, e.g., DM) [3].

Question 319: A patient with diabetic nephropathy developed secondary hyperparathyroidism. Hyperparathyroidism is seen in all of the following conditions, EXCEPT:

A. Osteoporosis (Correct Answer)
B. Osteomalacia
C. Rickets
D. Chronic renal failure

Explanation: **Explanation:** The core concept behind this question is the distinction between **metabolic bone diseases** that affect bone quality versus those that trigger a compensatory hormonal response. **Why Osteoporosis is the Correct Answer:** Osteoporosis is characterized by a decrease in **total bone mass** (both mineral and matrix are lost), but the remaining bone is biochemically normal. Crucially, serum levels of Calcium, Phosphate, and **Parathyroid Hormone (PTH) remain normal** in primary osteoporosis. There is no physiological trigger for hyperparathyroidism because there is no underlying vitamin D deficiency or hypocalcemia. **Analysis of Incorrect Options:** * **Chronic Renal Failure (CRF):** This is the classic cause of **Secondary Hyperparathyroidism**. In CRF, the kidneys fail to convert Vitamin D to its active form (1,25-OH₂D) and fail to excrete phosphate [1], [2]. The resulting hypocalcemia and hyperphosphatemia stimulate the parathyroid glands to overproduce PTH (Renal Osteodystrophy) [3]. * **Rickets (Children) and Osteomalacia (Adults):** Both conditions involve defective mineralization of the bone matrix, usually due to **Vitamin D deficiency** [2]. Low Vitamin D leads to decreased intestinal calcium absorption. The resulting hypocalcemia triggers a compensatory increase in PTH (Secondary Hyperparathyroidism) to maintain serum calcium levels [1]. **NEET-PG High-Yield Pearls:** 1. **Biochemical Profile of Osteoporosis:** Normal Ca²ⁱ, Normal PO₄³⁻, Normal ALP, Normal PTH. 2. **Secondary Hyperparathyroidism:** Characterized by **Low/Normal Calcium** and **High PTH** [2]. 3. **Tertiary Hyperparathyroidism:** Seen in long-standing CRF where the parathyroid glands become autonomous, leading to **High Calcium** and **Very High PTH** [3]. 4. **Hungry Bone Syndrome:** A common post-parathyroidectomy complication where sudden PTH withdrawal causes rapid calcium uptake by bones, leading to severe hypocalcemia.

Question 320: Dyslipidemia is more commonly associated with which type of diabetes mellitus?

A. Type 1 Diabetes Mellitus
B. Type 2 Diabetes Mellitus (Correct Answer)
C. Both Type 1 and Type 2 Diabetes Mellitus
D. Neither Type 1 nor Type 2 Diabetes Mellitus

Explanation: Type 2 Diabetes Mellitus (T2DM) is the correct answer because its pathophysiology is fundamentally linked to Insulin Resistance, which has a profound impact on lipid metabolism. In T2DM, insulin resistance leads to increased lipolysis in adipose tissue, elevating the flux of free fatty acids to the liver [2]. This stimulates the overproduction of Very Low-Density Lipoprotein (VLDL). Furthermore, the activity of Lipoprotein Lipase (LPL)—the enzyme responsible for clearing triglycerides—is reduced. This results in the classic "Diabetic Dyslipidemia" triad: Hypertriglyceridemia, low HDL levels, and the presence of small dense LDL particles. Analysis of Incorrect Options: * Type 1 Diabetes Mellitus (T1DM): While patients with poorly controlled T1DM can have hypertriglyceridemia (due to severe insulin deficiency causing LPL inactivity), those with good glycemic control often have a normal or even superior lipid profile (high HDL and low VLDL) compared to the general population. * Option C & D: These are incorrect because the prevalence and specific pattern of dyslipidemia are significantly more characteristic and frequent in the T2DM population due to the metabolic syndrome component [1]. Clinical Pearls for NEET-PG: * The "Atherogenic Triad": High Triglycerides + Low HDL + Small dense LDL. * Small dense LDL (Pattern B): These are more pro-atherogenic as they easily penetrate the arterial wall and are more susceptible to oxidation. * Target: In diabetic patients, the primary target of lipid-lowering therapy (Statins) is LDL cholesterol, regardless of the baseline level, due to the high cardiovascular risk. * Hypertriglyceridemia in DM is primarily due to increased VLDL production and decreased VLDL clearance.

Practice by Chapter

Diabetes Mellitus

Practice Questions

Thyroid Disorders

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Adrenal Gland Disorders

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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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