Endocrinology Practice Questions

Q: All of the following are causes of hypercalcemia except?

Hypothyroidism. 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].

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

None of the above. **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.

Q: 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?

Small cell carcinoma of the lung. **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).

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

Overnight low dose Dexamethasone suppression test. 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.

Q: What is the cause of polyuria?

Hyperglycemia. **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].

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

Osteoporosis. **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 1

A 29-year-old individual, a known diabetic on oral hypoglycemic agents for 3 years, has experienced weight loss and has never had diabetic ketoacidosis. Both his paternal grandfather and father are diabetic. Which of the following is the most likely diagnosis?

Accepted Answer

Maturity-onset diabetes of the young (MODY)

Answer

Type 1 Diabetes Mellitus

Answer

Type 2 Diabetes Mellitus

Answer

Pancreatic diabetes

Question 2

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

Accepted Answer

High intake of vitamin A

Answer

Sedentary lifestyle

Answer

Excessive intake of alcohol

Answer

Protein-energy malnutrition in infancy

Question 3

All of the following are causes of hypercalcemia except?

Accepted Answer

Hypothyroidism

Answer

Sarcoidosis

Answer

Bronchogenic carcinoma

Answer

Lithium toxicity

Question 4

Hyponatremia with isovolemia is seen in which condition?

Accepted Answer

Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion

Answer

Conn's syndrome

Answer

Cushing's syndrome

Answer

Furosemide therapy

Question 5

Hypertension is seen in all of the following conditions except?

Accepted Answer

None of the above

Answer

Adrenal tumors

Answer

Phaeochromocytoma

Answer

Conn's syndrome

Question 6

What is the most reliable test in the diagnosis of pheochromocytoma?

Accepted Answer

24-hour urinary metanephrine

Answer

Urinary catecholamines

Answer

Plasma catecholamines

Answer

Basal plasma catecholamines

Question 7

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?

Accepted Answer

Small cell carcinoma of the lung

Answer

Bronchogenic carcinoma

Answer

Thymoma

Answer

Renal cell carcinoma

Question 8

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

Accepted Answer

Overnight low dose Dexamethasone suppression test

Answer

High dose Dexamethasone suppression test

Answer

Corticotropin releasing hormone test

Answer

Insulin tolerance test

Question 9

What is the cause of polyuria?

Accepted Answer

Hyperglycemia

Answer

Hypoglycemia

Answer

Decreased fluid intake

Answer

Hypocalcemia

Question 10

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

Accepted Answer

Osteoporosis

Answer

Osteomalacia

Answer

Rickets

Answer

Chronic renal failure

Endocrinology — MCQs

Endocrinology — MCQs

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