Endocrinology — MCQs

A 56-year-old lady, a known case of lung cancer, presents with vomiting, headache, and seizures. Investigations reveal a serum osmolarity of 265 mosm/L (normal is 285-295 mosm/L), a serum sodium level of 125 mEq/L (normal value is 136-152 mEq/L), and urine osmolarity greater than 100 mOsm/L. She has normal water intake. Which of the following drugs is useful for this patient?

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 561: All of the following are true regarding primary hyperparathyroidism except?

A. Hypocalcemia (Correct Answer)
B. Hypophosphatemia
C. More than half of the patients are asymptomatic
D. Parathyroid adenoma is the commonest cause

Explanation: **Explanation:** Primary Hyperparathyroidism (PHPT) is characterized by the autonomous overproduction of Parathyroid Hormone (PTH), usually due to a single parathyroid adenoma [1]. **Why Option A is the Correct Answer (The "Except"):** In PHPT, the hallmark biochemical finding is **Hypercalcemia**, not hypocalcemia [2]. PTH increases serum calcium through three mechanisms [1]: 1. Increasing bone resorption (osteoclast activity). 2. Increasing renal tubular reabsorption of calcium. 3. Stimulating the synthesis of 1,25-dihydroxyvitamin D in the kidneys, which increases intestinal calcium absorption. **Analysis of Other Options:** * **Option B (Hypophosphatemia):** PTH inhibits the reabsorption of phosphate in the proximal convoluted tubule (phosphaturic effect), leading to low serum phosphate levels [1]. * **Option C (Asymptomatic Presentation):** In the modern era, **more than 50-80% of patients** are asymptomatic at the time of diagnosis, often discovered incidentally via routine biochemical screening [2]. * **Option D (Parathyroid Adenoma):** A solitary **parathyroid adenoma** is the most common cause (80-85%), followed by four-gland hyperplasia (10-15%) and parathyroid carcinoma (<1%) [3]. **NEET-PG High-Yield Pearls:** * **Classic Triad:** Hypercalcemia, elevated/inappropriately normal PTH, and hypophosphatemia [2]. * **Clinical Mnemonic:** "Stones (renal calculi), Bones (osteitis fibrosa cystica), Groans (abdominal pain/peptic ulcers), and Psychic Moans (depression/confusion)" [3]. * **Radiological Sign:** Subperiosteal bone resorption, most classically seen on the radial side of the middle phalanges. * **Treatment:** Surgical parathyroidectomy is the only curative treatment [3].

Question 562: A 42-year-old patient presents with obesity, glucose intolerance, hypertension, alkalosis, and proximal myopathy. Her ACTH levels did not drop after administering steroids. What is the diagnosis?

A. ACTH-producing tumor (Correct Answer)
B. Pituitary adenoma
C. Steroid supplementation
D. Adrenal tumor

Explanation: ### Explanation The patient presents with classic features of **Cushing’s Syndrome** [3] (obesity, glucose intolerance, hypertension, and proximal myopathy). The presence of **alkalosis** (specifically hypokalemic metabolic alkalosis) is a high-yield sign often associated with very high cortisol levels, typically seen in **Ectopic ACTH production** [2]. **1. Why "ACTH-producing tumor" is correct:** The key diagnostic clue is that ACTH levels **did not drop** after administering steroids (High-Dose Dexamethasone Suppression Test - HDDST). * In **Ectopic ACTH-producing tumors** (e.g., Small Cell Lung Cancer or Bronchial Carcinoid), the ACTH secretion is autonomous and does not respond to feedback inhibition by exogenous steroids [3]. * The severe metabolic alkalosis further points toward an ectopic source rather than a pituitary source. **2. Why other options are incorrect:** * **Pituitary Adenoma (Cushing’s Disease):** While this causes high ACTH, it typically shows **suppression** (>50% reduction in cortisol) during a High-Dose Dexamethasone Suppression Test because pituitary cells retain some sensitivity to feedback. * **Adrenal Tumor:** In primary adrenal tumors, the excess cortisol would **suppress** endogenous ACTH to undetectable levels via negative feedback [2]. The question implies ACTH is present and non-suppressible. [3] * **Steroid Supplementation (Exogenous):** This would cause "Iatrogenic Cushing’s," which results in low (suppressed) ACTH levels and bilateral adrenal atrophy [2]. **3. NEET-PG High-Yield Pearls:** * **Screening Test:** 24-hour urinary free cortisol or Low-Dose Dexamethasone Suppression Test (LDDST) [1]. * **Confirmatory/Localization:** HDDST helps differentiate Pituitary (suppresses) from Ectopic (no suppression) [2]. * **Hypokalemic Alkalosis:** Most common in Ectopic ACTH due to the mineralocorticoid effect of massive cortisol excess "overwhelming" the 11β-HSD2 enzyme in the kidneys. * **Hyperpigmentation:** Seen in ACTH-dependent causes (Pituitary/Ectopic) due to MSH-like activity, but absent in adrenal tumors.

Question 563: Which of the following is a symptom of hypothyroidism?

A. Intolerance to heat
B. Diarrhoea
C. Loss of weight
D. Menstrual disturbance - Menorrhagia (Correct Answer)

Explanation: Explanation: Hypothyroidism is characterized by a generalized slowing of metabolic processes due to a deficiency of thyroid hormones ($T_3$ and $T_4$). **Why Menorrhagia is correct:** In hypothyroidism, low levels of thyroid hormones lead to a decrease in the production of coagulation factors (like Factor VII, VIII, and IX) and a reduction in platelet adhesion. Furthermore, hypothyroidism can cause **hyperprolactinemia** (due to increased TRH stimulating lactotrophs) and altered LH/FSH pulsatility, leading to anovulatory cycles. The combination of impaired primary hemostasis and anovulation typically results in **Menorrhagia** (heavy menstrual bleeding). **Why the other options are incorrect:** * **A. Intolerance to heat:** This is a classic feature of **Hyperthyroidism** due to increased thermogenesis [1]. Hypothyroid patients suffer from **Cold intolerance**. * **B. Diarrhoea:** Hyperthyroidism increases gut motility, leading to frequent bowel movements or diarrhea. Hypothyroidism causes decreased motility, resulting in **Constipation**. * **C. Loss of weight:** Weight loss despite an increased appetite is hallmark of Hyperthyroidism [1]. Hypothyroidism leads to **Weight gain** due to a low basal metabolic rate (BMR) [1] and accumulation of glycosaminoglycans (myxedema). **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** Hashimoto’s Thyroiditis (look for anti-TPO antibodies). * **Early Sign:** Periorbital puffiness and slowing of the relaxation phase of deep tendon reflexes (**Woltman sign**). * **Lab Profile:** Elevated TSH is the most sensitive screening test for primary hypothyroidism. * **Dermatology:** "Peaches and cream" complexion due to hypercarotenemia.

Question 564: Ectopic ACTH syndrome is most commonly associated with which of the following conditions?

A. Renal cell carcinoma
B. Lymphoma
C. Bronchogenic carcinoma (Correct Answer)
D. Pituitary adenoma

Explanation: **Explanation:** **Ectopic ACTH Syndrome** occurs when a non-pituitary tumor secretes adrenocorticotropic hormone (ACTH), leading to hypercortisolism (Cushing’s syndrome) [1]. **1. Why Bronchogenic Carcinoma is Correct:** The most common cause of ectopic ACTH production is **Small Cell Carcinoma of the Lung (SCLC)**, a subtype of bronchogenic carcinoma [2], [3]. These tumors are derived from neuroendocrine cells (Kulchitsky cells) which have the metabolic machinery to synthesize and secrete polypeptide hormones like ACTH. Unlike pituitary-dependent Cushing’s disease, ectopic ACTH syndrome often presents with rapid onset, severe hypokalemia, and significant hyperpigmentation due to very high levels of ACTH and its precursor, POMC. **2. Analysis of Incorrect Options:** * **Renal cell carcinoma (A):** While RCC is a classic "great imitator" known for paraneoplastic syndromes (like Erythropoietin or PTHrP production), it is a rare cause of ectopic ACTH [2]. * **Lymphoma (B):** Lymphomas can occasionally cause hypercalcemia (via Vitamin D production), but they are not a primary source of ACTH. * **Pituitary adenoma (D):** A pituitary adenoma secreting ACTH is the cause of **Cushing’s Disease**. This is the most common cause of endogenous Cushing’s syndrome overall, but it is *not* considered "ectopic" because the pituitary is the physiological site of ACTH production [1]. **3. NEET-PG High-Yield Pearls:** * **Most common cause of Ectopic ACTH:** Small Cell Lung Cancer (SCLC) [3]. * **Second most common cause:** Bronchial Carcinoid tumors. * **Biochemical Hallmark:** High-dose dexamethasone suppression test (HDDST) fails to suppress cortisol levels in ectopic ACTH (unlike Cushing’s Disease, where suppression occurs). * **Clinical Clue:** If a patient has Cushingoid features plus profound **hypokalemic metabolic alkalosis**, suspect ectopic ACTH.

Question 565: In Multiple Endocrine Neoplasia type I (MEN I), which of the following tumors is seen most commonly?

A. Insulinoma
B. Gastrinoma (Correct Answer)
C. Glucagonoma
D. Somatostatinoma

Explanation: Explanation: Multiple Endocrine Neoplasia type I (MEN I), also known as **Wermer’s Syndrome**, is characterized by the "3 Ps": **P**arathyroid hyperplasia (most common overall manifestation), **P**ituitary adenomas, and **P**ancreatic neuroendocrine tumors (NETs). **Why Gastrinoma is correct:** Among the pancreatic neuroendocrine tumors associated with MEN I, **Gastrinoma** is the most common functional tumor. It typically presents as **Zollinger-Ellison Syndrome (ZES)**, characterized by refractory peptic ulcers and diarrhea. While non-functional tumors are technically the most frequent pancreatic lesions found on imaging/autopsy, Gastrinoma remains the most common symptomatic/functional pancreatic tumor in MEN I patients. **Analysis of Incorrect Options:** * **A. Insulinoma:** This is the second most common functional pancreatic NET in MEN I. It presents with fasting hypoglycemia (Whipple’s triad). * **C. Glucagonoma:** These are rare in MEN I. They present with the "4 Ds": Diabetes, Dermatitis (Necrolytic migratory erythema), Deep vein thrombosis, and Depression. * **D. Somatostatinoma:** These are extremely rare and typically present with a triad of diabetes mellitus, cholelithiasis, and steatorrhea. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Dominant; mutation in the *MEN1* gene (Menin protein) on Chromosome 11q13. * **Most Common Initial Manifestation:** Hyperparathyroidism (seen in >95% of patients by age 30). * **Gastrinoma Location:** In MEN I, gastrinomas are frequently multiple and often located in the **duodenum** (Gastrinoma Triangle) rather than the pancreas. * **Pituitary:** Prolactinoma is the most common pituitary tumor in MEN I.

Question 566: Which of the following can cause hypercalcemia?

A. Thyrotoxicosis
B. Vitamin D intoxication
C. Thiazide diuretics
D. All of the above (Correct Answer)

Explanation: ### Explanation Hypercalcemia is a common clinical finding in endocrinology, resulting from increased bone resorption, enhanced gastrointestinal absorption, or decreased renal excretion of calcium. **1. Thyrotoxicosis (Option A):** Excess thyroid hormone (T3/T4) has a direct stimulatory effect on osteoclasts, leading to increased bone turnover and resorption. This releases calcium into the bloodstream [2]. Approximately 15-20% of thyrotoxic patients exhibit mild hypercalcemia [2]. **2. Vitamin D Intoxication (Option B):** Vitamin D increases calcium levels via two primary mechanisms: enhancing intestinal calcium absorption and stimulating osteoclast-mediated bone resorption [1]. Excessive intake leads to significant hypercalcemia and hypercalciuria [2]. **3. Thiazide Diuretics (Option C):** Unlike loop diuretics (which are "calciuric"), thiazides increase calcium reabsorption in the distal convoluted tubule of the kidney [1]. While they rarely cause severe hypercalcemia alone, they can unmask underlying primary hyperparathyroidism [2]. **Conclusion:** Since all three mechanisms lead to elevated serum calcium, **Option D** is the correct answer. --- ### NEET-PG Clinical Pearls * **Most Common Cause:** In outpatient settings, **Primary Hyperparathyroidism** (usually due to an adenoma) is the most common cause [2]. In hospitalized patients, **Malignancy** is the leading cause [2]. * **Mnemonic for Symptoms:** "Stones (renal), Bones (aches), Groans (abdominal pain/constipation), and Psychic Moans (confusion/depression)." * **ECG Finding:** Hypercalcemia causes a **shortened QT interval**. * **Differential Tip:** To differentiate between causes, always check the **PTH level** [2]. If PTH is low (suppressed), look for malignancy, Vitamin D toxicity, or sarcoidosis [2]. If PTH is high/normal, it is likely PTH-mediated (e.g., Primary Hyperparathyroidism) [2].

Question 567: Which insulin preparation has the longest duration of action?

A. Aspart
B. Lispro
C. Glargine (Correct Answer)
D. NPH

Explanation: ### Explanation The duration of action of insulin preparations is determined by their rate of absorption from the subcutaneous tissue into the bloodstream. **Correct Answer: C. Glargine** Insulin Glargine is a **long-acting (basal) insulin analog**. It is designed to be soluble at an acidic pH (pH 4) but precipitates into micro-crystals upon injection into the neutral pH of subcutaneous tissue [1]. These crystals dissolve slowly, providing a relatively peakless, constant level of insulin for **up to 24 hours** [1]. This makes it ideal for maintaining basal glycemic control. **Why the other options are incorrect:** * **A & B (Aspart and Lispro):** These are **rapid-acting insulin analogs**. They are designed to dissociate rapidly into monomers after injection, leading to a quick onset (15 mins) and a very short duration of action (3–5 hours) [1]. They are used primarily for postprandial (mealtime) glucose control. * **D (NPH):** Neutral Protamine Hagedorn (NPH) is an **intermediate-acting insulin**. The addition of protamine delays its absorption, resulting in a duration of action of approximately 12–18 hours [1]. It has a distinct peak (4–10 hours), which increases the risk of nocturnal hypoglycemia compared to Glargine. **NEET-PG High-Yield Pearls:** * **Ultra-long acting:** If **Degludec** or **Glargine U-300** were options, they would be the correct answer as their duration exceeds 42 hours and 36 hours, respectively. * **Peakless Profile:** Glargine and Detemir are often called "peakless" insulins, reducing the risk of hypoglycemia [1, 2]. * **Mixing:** Glargine should **not** be mixed in the same syringe with other insulins because its low pH can cause the other insulin to precipitate. * **Inhaled Insulin (Afrezza):** Has the fastest onset of action among all preparations.

Question 568: Addison's disease is characterized by all of the following except?

A. Hyperglycemia (Correct Answer)
B. Hypotension
C. Hyperkalemia
D. Hyponatremia

Explanation: **Explanation:** Addison’s disease (Primary Adrenocortical Insufficiency) results from the destruction of the adrenal cortex, leading to a deficiency of both **cortisol** (glucocorticoid) and **aldosterone** (mineralocorticoid) [1]. **1. Why Hyperglycemia is the correct answer:** Cortisol is a "stress hormone" and a potent gluconeogenic agent. It increases blood glucose by stimulating gluconeogenesis in the liver and decreasing peripheral glucose uptake. Therefore, a deficiency of cortisol in Addison’s disease leads to **hypoglycemia**, not hyperglycemia. **2. Analysis of other options:** * **Hypotension:** This occurs due to two reasons: (a) Aldosterone deficiency leads to sodium and water wasting (volume depletion), and (b) Cortisol deficiency results in decreased vascular reactivity to catecholamines. * **Hyperkalemia:** Aldosterone normally acts on the distal renal tubules to excrete potassium and reabsorb sodium. Its absence leads to potassium retention. * **Hyponatremia:** This is the most common electrolyte abnormality in Addison’s. It is caused by renal sodium wasting (due to low aldosterone) and increased ADH secretion (due to low cortisol), which leads to water retention. **Clinical Pearls for NEET-PG:** * **Hyperpigmentation:** A hallmark of primary adrenal insufficiency (due to increased ACTH/MSH), seen in skin creases, buccal mucosa, and scars [2]. It is **absent** in secondary adrenal insufficiency. * **Acid-Base Balance:** Addison’s is associated with **Normal Anion Gap Metabolic Acidosis** (due to decreased H+ excretion). * **Diagnosis:** The most specific initial test is the **ACTH Stimulation Test** (Cosyntropin test) [2]. * **Crisis Management:** Acute adrenal crisis is a medical emergency treated with aggressive IV fluids (Normal Saline) and IV **Hydrocortisone** [2].

Question 569: Which of the following conditions is most likely associated with the described clinical scenario?

A. Vitamin D intoxication
B. Acromegaly
C. Hyperparathyroidism (Correct Answer)
D. None of the above

Explanation: The correct answer is **Hyperparathyroidism**. This condition is characterized by the overproduction of Parathyroid Hormone (PTH), which leads to hypercalcemia through three primary mechanisms: increased bone resorption (osteoclast activation), increased renal calcium reabsorption, and increased intestinal calcium absorption (via stimulation of Vitamin D activation) [1]. **Why Hyperparathyroidism is correct:** Primary hyperparathyroidism is the most common cause of outpatient hypercalcemia [2]. It typically presents with the classic mnemonic **"Stones, Bones, Abdominal Groans, and Psychic Moans"** (nephrolithiasis, osteitis fibrosa cystica, peptic ulcers/pancreatitis, and depression/confusion) [3], [4]. Laboratory findings typically show elevated serum calcium and inappropriately elevated or high-normal PTH levels [2]. **Why other options are incorrect:** * **Vitamin D Intoxication:** While this also causes hypercalcemia, it results in **suppressed PTH levels** due to negative feedback [2]. It is characterized by high levels of 25-hydroxyvitamin D. * **Acromegaly:** While growth hormone excess can occasionally cause mild hypercalciuria (due to increased bone turnover), it is not a primary or common cause of significant hypercalcemia unless associated with **MEN-1 syndrome** (where co-existing parathyroid adenomas occur) [2]. **NEET-PG High-Yield Pearls:** * **Most common cause:** Solitary parathyroid adenoma (85%). * **Radiological Hallmark:** Subperiosteal bone resorption, most commonly seen on the radial aspect of the middle phalanges. * **Brown Tumors:** These are non-neoplastic cystic lesions of the bone caused by intense osteoclast activity in severe hyperparathyroidism. * **Hungry Bone Syndrome:** A risk of post-operative hypocalcemia following parathyroidectomy as the "starved" bones rapidly take up calcium [4].

Question 570: A 56-year-old lady, a known case of lung cancer, presents with vomiting, headache, and seizures. Investigations reveal a serum osmolarity of 265 mosm/L (normal is 285-295 mosm/L), a serum sodium level of 125 mEq/L (normal value is 136-152 mEq/L), and urine osmolarity greater than 100 mOsm/L. She has normal water intake. Which of the following drugs is useful for this patient?

A. Acetazolamide
B. Hydrochlorothiazide
C. Triamterene
D. Tolvaptan (Correct Answer)

Explanation: ### Explanation **Diagnosis: SIADH (Syndrome of Inappropriate Antidiuretic Hormone)** The patient presents with **hypotonic hyponatremia** (Serum Na+ 125 mEq/L, Osmolarity 265 mOsm/L) and inappropriately concentrated urine (Urine Osmolarity >100 mOsm/L) in the setting of lung cancer (likely Small Cell Lung Cancer, a common cause of ectopic ADH). The neurological symptoms (seizures, headache) indicate severe/symptomatic hyponatremia [2]. **Why Tolvaptan is Correct:** Tolvaptan is a **selective oral Vasopressin V2-receptor antagonist** (an "Aquaretic"). It works by blocking the action of ADH at the collecting ducts, leading to the excretion of electrolyte-free water [1]. It is specifically indicated for euvolemic hyponatremia (SIADH) when fluid restriction is insufficient or the patient is symptomatic. **Why Other Options are Incorrect:** * **Acetazolamide (A):** A carbonic anhydrase inhibitor used for glaucoma and altitude sickness. It can actually worsen hyponatremia by increasing sodium excretion. * **Hydrochlorothiazide (B):** Thiazide diuretics are a **common cause** of hyponatremia [2]. They inhibit sodium reabsorption in the distal tubule while preserving the medullary gradient, leading to water retention. * **Triamterene (C):** A potassium-sparing diuretic that acts on ENaC channels. It does not address the underlying pathophysiology of ADH excess and is not used to treat SIADH. **Clinical Pearls for NEET-PG:** * **Small Cell Lung Cancer** is the most common malignancy associated with SIADH. * **Management Strategy:** * *Mild/Asymptomatic:* Fluid restriction [1]. * *Moderate/Chronic:* Vaptans (Tolvaptan, Conivaptan) or Demeclocycline [1]. * *Severe/Emergency (Seizures/Coma):* Hypertonic saline (3% NaCl). * **Caution:** Always correct sodium slowly (<8–10 mEq/L in 24 hours) to avoid **Osmotic Demyelination Syndrome** (Central Pontine Myelinolysis) [1].

Practice by Chapter

Diabetes Mellitus

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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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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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