Endocrinology — MCQs

A 25-year-old woman presents with recurrent episodes of headache and sweating. Her mother had a history of renal calculi and died due to a neck mass. Physical examination reveals a thyroid nodule, but there are no clinical signs of thyrotoxicosis. What should be ordered before performing thyroid surgery?

Q265Easy

What is the most useful investigation in the diagnosis of diabetic ketoacidosis?

Q266Easy

What are the classic symptoms of diabetes mellitus?

Q267Medium

A young female presents with hypertension and VMA > 14 mg/day. Which of the following conditions are associated with this presentation?

Q268Medium

High calcium intake can lead to which of the following conditions?

Q269Easy

Excess aldosterone is associated with all the following except?

Q270Medium

What are the typical laboratory values for a patient with central diabetes insipidus (Urinary Osmolality & Serum Osmolality)?

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 261: Laboratory investigations of a patient show excess T4 and decreased TSH. Which of the following is the most likely diagnosis?

A. Graves' disease (Correct Answer)
B. Hashimoto's disease
C. Pituitary failure
D. Hypothalamic failure

Explanation: **Explanation:** The laboratory findings of **elevated T4 (Hyperthyroidism)** and **decreased TSH** indicate **Primary Hyperthyroidism**. In this state, the thyroid gland autonomously overproduces hormones, which then exert negative feedback on the anterior pituitary, suppressing TSH secretion. **1. Why Graves' Disease is Correct:** Graves' disease is the most common cause of primary hyperthyroidism. It is an autoimmune disorder where **TSH-receptor antibodies (TRAb)** mimic TSH and continuously stimulate the thyroid gland to produce excess T4 and T3. This high level of circulating thyroid hormone suppresses TSH to subnormal or undetectable levels. **2. Why the Other Options are Incorrect:** * **Hashimoto’s Disease:** This is the most common cause of **Primary Hypothyroidism**. It typically presents with **low T4 and high TSH** due to autoimmune destruction of the thyroid gland. * **Pituitary Failure (Secondary Hypothyroidism):** Failure of the pituitary gland results in **low TSH**, which subsequently leads to **low T4**. * **Hypothalamic Failure (Tertiary Hypothyroidism):** Failure of the hypothalamus leads to decreased TRH, resulting in **low TSH and low T4**. **Clinical Pearls for NEET-PG:** * **Primary vs. Secondary:** If TSH and T4 move in **opposite** directions, the pathology is **Primary** (Thyroid gland). If they move in the **same** direction, the pathology is **Central** (Pituitary/Hypothalamus). * **Graves' Triad:** Hyperthyroidism, Exophthalmos (Ophthalmopathy), and Pretibial Myxedema (Dermopathy). * **Amiodarone:** Can cause both hyperthyroidism (Type 1 and 2 Jod-Basedow) and hypothyroidism (Wolff-Chaikoff effect). * **Subclinical Hyperthyroidism:** Defined as a low TSH with **normal** T4 and T3 levels.

Question 262: 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 endocrine emergency characterized by extreme hypermetabolism. The management follows a specific sequence to inhibit thyroid hormone synthesis, release, and peripheral action. **Why Reserpine is the Correct Answer:** Historically, **Reserpine** (and Guanethidine) were used to deplete catecholamines in thyrotoxicosis. However, they are **no longer used** in modern clinical practice due to their slow onset of action and significant side effects, such as profound hypotension, sedation, and depression. In the context of current NEET-PG standards and clinical guidelines (ATA/ETA), Reserpine is considered obsolete. **Analysis of Incorrect Options:** * **Potassium Iodide (SSKI/Lugol’s):** Used to inhibit the release of preformed thyroid hormones (the **Wolff-Chaikoff effect**). It must be given at least 1 hour *after* antithyroid drugs to prevent the iodine from being used as a substrate for new hormone synthesis. * **Propranolol:** A mainstay of treatment [1]. It controls sympathetic overactivity (tachycardia, tremors) and, at high doses, uniquely inhibits the peripheral conversion of T4 to the more active T3. * **Calcium Channel Blockers (CCBs):** While Beta-blockers are first-line, non-dihydropyridine CCBs (like **Diltiazem**) are recommended alternatives for heart rate control in patients where Beta-blockers are contraindicated (e.g., severe asthma or COPD). **High-Yield Clinical Pearls for NEET-PG:** 1. **Sequence of Treatment:** 1. Propylthiouracil (PTU) → 2. Iodine → 3. Beta-blockers → 4. Steroids (Dexamethasone/Hydrocortisone). 2. **PTU vs. Methimazole:** PTU is preferred in thyroid storm because it inhibits both hormone synthesis and peripheral T4 to T3 conversion [1]. 3. **Burch-Wartofsky Point Scale:** Used clinically to diagnose thyroid storm (Score >45 is highly suggestive). 4. **Steroids:** Added to the regimen to treat potential relative adrenal insufficiency and further inhibit T4 to T3 conversion.

Question 263: A 50-year-old man with a history of type 2 diabetes mellitus asks about the chances that his children will inherit this metabolic disorder. The patient is told that he has a genetic disease that shows which of the following patterns of inheritance?

A. Autosomal dominant
B. Autosomal recessive
C. Multifactorial (Correct Answer)
D. X-linked dominant

Explanation: **Explanation:** **1. Why Multifactorial is Correct:** Type 2 Diabetes Mellitus (T2DM) is a classic example of a **multifactorial (polygenic) inheritance** pattern [1]. Unlike monogenic disorders, T2DM results from the complex interplay between **multiple susceptibility genes** and **environmental factors** (such as obesity, sedentary lifestyle, and diet) [1]. While T2DM has a stronger genetic component than Type 1 DM—with a concordance rate of 70-90% in monozygotic twins—it does not follow a simple Mendelian pattern. If one parent has T2DM, the risk to the offspring is approximately 15-40%. **2. Why Other Options are Incorrect:** * **Autosomal Dominant (AD):** While **MODY** (Maturity-Onset Diabetes of the Young) follows an AD pattern due to single-gene mutations (e.g., HNF1-alpha, Glucokinase), it represents only 1-5% of diabetes cases and is distinct from common T2DM. * **Autosomal Recessive (AR):** AR inheritance requires two copies of a mutated gene. T2DM risk is cumulative across many loci and influenced by lifestyle, making this pattern inapplicable. * **X-linked Dominant:** This would involve a specific inheritance pattern linked to the X chromosome (e.g., Alport syndrome), which is not observed in the epidemiology of T2DM. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genetic Risk:** If both parents have T2DM, the risk to offspring increases to nearly **60-75%**. * **Twin Concordance:** Monozygotic twins (70-90%) vs. Dizygotic twins (20-30%). * **HLA Association:** T2DM has **no** strong association with HLA markers, unlike Type 1 DM (associated with HLA-DR3 and DR4) [2]. * **MODY vs. T2DM:** Always look for "strong family history in 3 consecutive generations" and "young age of onset (<25 years)" to differentiate MODY (AD) from T2DM (Multifactorial).

Question 264: A 25-year-old woman presents with recurrent episodes of headache and sweating. Her mother had a history of renal calculi and died due to a neck mass. Physical examination reveals a thyroid nodule, but there are no clinical signs of thyrotoxicosis. What should be ordered before performing thyroid surgery?

A. Measurement of thyroid hormones
B. Serial determinations of serum calcium, phosphorus, protein, and alkaline phosphatase
C. 24-hour urine test for 5-hydroxyindoleacetic acid excretion
D. Serial 24-hour tests for catecholamines, metanephrines, and vanillylmandelic acid excretion (Correct Answer)

Explanation: ### Explanation The clinical presentation strongly suggests **Multiple Endocrine Neoplasia Type 2A (MEN 2A)**, also known as Sipple Syndrome. This autosomal dominant condition is characterized by the triad of **Medullary Thyroid Carcinoma (MTC)**, **Pheochromocytoma**, and **Parathyroid Hyperplasia**. **Why Option D is Correct:** The patient has a thyroid nodule (likely MTC) and symptoms of headache and sweating (classic for Pheochromocytoma) [1]. Her mother’s history of "renal calculi" suggests hypercalcemia/parathyroid disease, and the "neck mass" suggests MTC [1]. In any patient suspected of MEN 2A, **Pheochromocytoma must be ruled out or treated before any surgery.** If a patient with an undiagnosed pheochromocytoma undergoes surgery, the induction of anesthesia or surgical stress can trigger a life-threatening **hypertensive crisis**. Therefore, 24-hour urinary catecholamines and metanephrines are the mandatory first step. **Why Other Options are Incorrect:** * **Option A:** Thyroid hormone levels are usually normal in MTC, as the tumor arises from parafollicular C-cells, not follicular cells. * **Option B:** While these tests evaluate parathyroid function, they are not the immediate priority before surgery compared to the risk of a hypertensive crisis [1]. * **Option C:** 5-HIAA is a marker for Carcinoid syndrome, which presents with flushing and diarrhea, not the episodic hypertension/headache seen here. ### NEET-PG High-Yield Pearls * **MEN 2A (Sipple Syndrome):** MTC (100%), Pheochromocytoma (50%), Parathyroid Hyperplasia (20%). * **MEN 2B:** MTC, Pheochromocytoma, Mucosal Neuromas, and Marfanoid habitus. * **Rule of Thumb:** Always "Rule out Pheo" before operating on MTC or any other condition in a MEN patient [1]. * **Genetic Marker:** Mutations in the **RET proto-oncogene** are diagnostic for MEN 2. * **Tumor Marker for MTC:** Serum **Calcitonin** and CEA.

Question 265: What is the most useful investigation in the diagnosis of diabetic ketoacidosis?

A. Ketonemia (Correct Answer)
B. pH of blood
C. Urinary sugar
D. Urine ketone

Explanation: Diabetic Ketoacidosis (DKA) is defined by the biochemical triad of **hyperglycemia, ketosis, and metabolic acidosis**. While all these components are necessary for diagnosis, **ketonemia** (specifically the measurement of serum beta-hydroxybutyrate) is the most useful and definitive investigation for confirming the diagnosis and monitoring treatment. [1] * **Why Ketonemia is correct:** Beta-hydroxybutyrate (β-OHB) is the predominant ketone body in DKA. Serum testing is more sensitive and specific than urine testing. It provides a real-time reflection of the metabolic state, as it rises earliest during onset and falls rapidly with effective insulin therapy. * **Why pH of blood is incorrect:** While a low pH (acidosis) is a hallmark of DKA, it is non-specific. Acidosis can occur in many other conditions (e.g., lactic acidosis, uremia, or sepsis) without the presence of ketones. * **Why Urinary sugar is incorrect:** Glucosuria simply indicates that the blood glucose has exceeded the renal threshold (~180 mg/dL). It does not differentiate between simple hyperglycemia and life-threatening DKA. * **Why Urine ketone is incorrect:** Urine tests use the nitroprusside reaction, which detects **acetoacetate** but not β-OHB. In early DKA, the ratio of β-OHB to acetoacetate is high (up to 10:1), meaning urine tests can yield a **false negative** or underestimate the severity of ketosis. **Clinical Pearls for NEET-PG:** * **Diagnostic Criteria:** Blood glucose >250 mg/dL, pH <7.3, Bicarbonate <18 mEq/L, and positive ketones [1]. * **Best Marker for Monitoring:** Serum beta-hydroxybutyrate is the preferred marker to track the resolution of DKA. [2] * **Anion Gap:** DKA is a classic cause of **High Anion Gap Metabolic Acidosis (HAGMA)**. * **Management Priority:** The first step in management is always **aggressive fluid resuscitation** (Normal Saline), followed by insulin infusion and potassium correction. [1]

Question 266: What are the classic symptoms of diabetes mellitus?

A. Polydipsia
B. Polyuria
C. Polyphagia
D. All of the above (Correct Answer)

Explanation: The classic presentation of Diabetes Mellitus (DM) is characterized by the "3 Ps": **Polydipsia, Polyuria, and Polyphagia.** [1] **Pathophysiology of the 3 Ps:** 1. **Polyuria (Increased Urination):** When blood glucose levels exceed the renal threshold (approximately 180 mg/dL), glucose is excreted in the urine (glucosuria). [3] Glucose acts as an osmotic diuretic, pulling water with it, leading to excessive urine production. [2] 2. **Polydipsia (Increased Thirst):** The massive loss of water via polyuria leads to intracellular dehydration and increased serum osmolality. [2] This stimulates the thirst center in the hypothalamus, causing the patient to drink excessive amounts of water. 3. **Polyphagia (Increased Hunger):** Despite high circulating glucose, the lack of insulin (Type 1) or insulin resistance (Type 2) prevents glucose from entering the cells. [1] The body perceives this as a state of starvation, triggering the hunger center. **Why "All of the above" is correct:** Since all three symptoms are direct physiological consequences of hyperglycemia and insulin deficiency/resistance, they frequently occur together in the clinical presentation of DM. [2] **High-Yield Clinical Pearls for NEET-PG:** * **Weight Loss:** Despite polyphagia, patients (especially Type 1 DM) often experience weight loss due to the depletion of fat and protein stores (catabolic state). [2] * **Renal Threshold:** Remember the value of **180 mg/dL**; glucosuria typically does not occur until blood glucose crosses this limit. [3] * **Blurred Vision:** Often a presenting symptom due to osmotic changes in the lens of the eye. [2] * **Diagnostic Criteria:** HbA1c ≥ 6.5%, Fasting Plasma Glucose ≥ 126 mg/dL, or 2-hour Plasma Glucose ≥ 200 mg/dL during an OGTT. [3]

Question 267: A young female presents with hypertension and VMA > 14 mg/day. Which of the following conditions are associated with this presentation?

A. Medullary carcinoma of the thyroid, Von Hippel-Lindau disease, Sturge-Weber syndrome, Grave's disease
B. Medullary carcinoma of the thyroid, Von Hippel-Lindau disease, Sturge-Weber syndrome, Neurofibromatosis
C. Medullary carcinoma of the thyroid, Sturge-Weber syndrome, Grave's disease, Neurofibromatosis
D. Medullary carcinoma of the thyroid, Von Hippel-Lindau disease, Grave's disease, Neurofibromatosis (Correct Answer)

Explanation: **Explanation:** The clinical presentation of **hypertension** combined with elevated urinary **VMA (>14 mg/day)**— a metabolite of catecholamines—is diagnostic of **Pheochromocytoma**. This tumor of the chromaffin cells is famously known as the "10% tumor" and is frequently associated with specific familial syndromes [1]. **1. Why Option D is Correct:** Pheochromocytoma is a key component of several genetic neuro-endocrine syndromes [1]: * **MEN 2A and 2B:** Associated with **Medullary Carcinoma of the Thyroid (MCT)**. * **Von Hippel-Lindau (VHL) Disease:** Associated with hemangioblastomas and renal cell carcinoma. * **Neurofibromatosis Type 1 (NF1):** Approximately 1% of NF1 patients develop pheochromocytoma. * **Grave’s Disease:** While not a genetic "syndrome" link like MEN, there is a documented clinical association where hyperthyroidism can coexist with or mimic the hyperadrenergic state of pheochromocytoma. **2. Why Other Options are Incorrect:** * **Sturge-Weber Syndrome (Options A, B, and C):** This is a phakomatosis characterized by port-wine stains and leptomeningeal angiomas. Unlike NF1 or VHL, it has **no established association** with pheochromocytoma. Its inclusion makes these options incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Rule of 10s:** 10% are bilateral, 10% are extra-adrenal (Paragangliomas), 10% are malignant, and 10% are familial. * **Screening:** Urinary or plasma **Metanephrines** are more sensitive than VMA for initial screening. * **Pre-op Management:** Always start **Alpha-blockers (Phenoxybenzamine)** before Beta-blockers to avoid a hypertensive crisis (unopposed alpha stimulation). * **Localization:** MIBG scan is used if CT/MRI fails to locate the tumor [1].

Question 268: High calcium intake can lead to which of the following conditions?

A. Osteoporosis
B. Osteopetrosis
C. Milk alkali syndrome (Correct Answer)
D. Renal failure

Explanation: **Explanation:** **Milk-Alkali Syndrome (MAS)** is the correct answer. It is a clinical triad of **hypercalcemia, metabolic alkalosis, and acute kidney injury** caused by the excessive ingestion of calcium (usually as calcium carbonate) and absorbable alkali [2]. 1. **Mechanism:** High intake of calcium carbonate leads to hypercalcemia. Hypercalcemia causes renal vasoconstriction and inhibits the Na-K-2Cl cotransporter (inducing natriuresis and volume depletion). This volume depletion stimulates bicarbonate reabsorption, leading to metabolic alkalosis [3]. Alkalosis, in turn, enhances calcium reabsorption in the distal tubule, creating a vicious cycle that further elevates serum calcium levels. **Analysis of Incorrect Options:** * **A. Osteoporosis:** This is characterized by low bone mineral density. High calcium intake is actually a preventive measure or adjunct treatment for osteoporosis, not a cause [1]. * **B. Osteopetrosis:** This is a rare genetic "marble bone" disease caused by defective osteoclast function, leading to overly dense but brittle bones. It is not caused by dietary calcium intake. * **D. Renal Failure:** While MAS can *lead* to renal failure (as part of the triad), "Renal failure" as a standalone option is less specific than the syndrome itself. In the context of high calcium/alkali intake, MAS is the primary diagnosis [2]. **NEET-PG High-Yield Pearls:** * **Modern Etiology:** Historically caused by milk/antacids for peptic ulcers; currently, the most common cause is over-the-counter **calcium carbonate** supplements used for osteoporosis prevention. * **Clinical Presentation:** Patients may present with confusion, polyuria, polydipsia, and vomiting. * **ECG Finding:** Hypercalcemia typically causes a **shortened QT interval**. * **Treatment:** Aggressive hydration with isotonic saline and discontinuation of the offending agents.

Question 269: Excess aldosterone is associated with all the following except?

A. Hypokalemia
B. Hyperkalemia (Correct Answer)
C. Sodium retention
D. Hypertension

Explanation: **Explanation:** The physiological hallmark of **Aldosterone** (a mineralocorticoid) is its action on the **Principal cells** of the late distal tubule and collecting duct in the kidney [1], [4]. It stimulates the **ENaC (Epithelial Sodium Channels)** and the **Na+/K+ ATPase pump**, leading to the reabsorption of Sodium (Na+) and the excretion of Potassium (K+) and Hydrogen ions (H+) [1], [4]. **Why Hyperkalemia is the correct answer (the "Except"):** Since aldosterone promotes the active secretion of potassium into the tubular lumen for excretion, an excess of aldosterone (as seen in Primary Hyperaldosteronism or Conn’s Syndrome) leads to **Hypokalemia**, not hyperkalemia [1], [3]. Therefore, Option B is the incorrect association. **Analysis of other options:** * **A. Hypokalemia:** This is a classic finding due to increased renal K+ wasting [3]. * **C. Sodium retention:** Aldosterone increases Na+ reabsorption [4]. While this leads to volume expansion, clinical edema is usually absent due to the **"Aldosterone Escape"** phenomenon (where ANP release leads to pressure natriuresis) [2]. * **D. Hypertension:** Increased sodium and water retention lead to expanded extracellular fluid volume, resulting in hypertension (typically with low plasma renin levels) [2]. **NEET-PG High-Yield Pearls:** 1. **Metabolic Alkalosis:** Excess aldosterone also stimulates H+ secretion via α-intercalated cells, leading to metabolic alkalosis [1], [3]. 2. **Conn’s Syndrome Triad:** Hypertension, Hypokalemia, and Metabolic Alkalosis [3]. 3. **Screening:** The best initial test for Primary Hyperaldosteronism is the **Aldosterone-to-Renin Ratio (ARR)**. 4. **Treatment:** Spironolactone or Eplerenone (Aldosterone antagonists) are the drugs of choice for bilateral adrenal hyperplasia.

Question 270: What are the typical laboratory values for a patient with central diabetes insipidus (Urinary Osmolality & Serum Osmolality)?

A. Urinary Osmolality: 50 mOsm/kg, Serum Osmolality: 300 mOsm/kg (Correct Answer)
B. Urinary Osmolality: 500 mOsm/kg, Serum Osmolality: 260 mOsm/kg
C. Urinary Osmolality: 50 mOsm/kg, Serum Osmolality: 260 mOsm/kg
D. Urinary Osmolality: 500 mOsm/kg, Serum Osmolality: 100 mOsm/kg

Explanation: ### Explanation **1. Understanding the Core Concept** Diabetes Insipidus (DI) is characterized by a deficiency of Antidiuretic Hormone (ADH) in Central DI or resistance to it in Nephrogenic DI. ADH normally acts on the V2 receptors in the renal collecting ducts to reabsorb water [3]. In its absence, the kidneys cannot concentrate urine, leading to the excretion of large volumes of dilute urine (**Polyuria**) and a subsequent rise in serum concentration (**Hypernatremia/Hyperosmolality**) [1], [2]. **2. Why Option A is Correct** * **Urinary Osmolality (50 mOsm/kg):** Because water is not being reabsorbed, the urine remains extremely dilute. Typical DI values are <200 mOsm/kg (often as low as 50–100). * **Serum Osmolality (300 mOsm/kg):** Excessive water loss in urine leads to hemoconcentration. Normal serum osmolality is 275–295 mOsm/kg; in DI, it typically exceeds 295–300 mOsm/kg [1], [2]. **3. Analysis of Incorrect Options** * **Option B & D:** These show high urinary osmolality (500 mOsm/kg). This indicates concentrated urine, which rules out DI [3]. * **Option C:** Shows low urinary osmolality (correct for DI) but low serum osmolality (260 mOsm/kg). Low serum osmolality is characteristic of **SIADH** or **Primary Polydipsia**, not DI [2]. **4. NEET-PG High-Yield Pearls** * **Gold Standard Diagnosis:** Water Deprivation Test [2]. * **Differentiation:** After administering Desmopressin (ADH analogue), Central DI shows a **>50% increase** in urine osmolality, whereas Nephrogenic DI shows little to no response [2]. * **Drug of Choice:** Desmopressin (DDAVP) for Central DI; Thiazides/Amiloride for Nephrogenic DI [2]. * **MRI Finding:** Loss of the

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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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Multiple Endocrine Neoplasia

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Obesity and Metabolic Syndrome

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Endocrine Emergencies

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