Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 1271: Which of the following is seen in Vitamin D deficiency?

A. Increased alkaline phosphatase (Correct Answer)
B. Decreased phosphate in urine
C. Hyperphosphatemia
D. Decreased alkaline phosphatase

Explanation: Vitamin D deficiency leads to decreased intestinal absorption of calcium and phosphate [1]. This triggers a physiological cascade essential for NEET-PG preparation: 1. **Why Option A is Correct:** Low serum calcium stimulates the parathyroid glands to secrete **Parathyroid Hormone (PTH)** (Secondary Hyperparathyroidism) [2]. PTH increases bone remodeling and osteoblastic activity to mobilize calcium. **Alkaline Phosphatase (ALP)** is a byproduct of osteoblastic activity; therefore, its levels rise significantly as the bone attempts to compensate for the mineral deficit. This is often the earliest biochemical marker of osteomalacia/rickets. 2. **Why Options B and C are Incorrect:** * **Hypophosphatemia (Not Hyperphosphatemia):** While Vitamin D deficiency reduces phosphate absorption, the secondary hyperparathyroidism further worsens this by causing **phosphaturia** (increased phosphate excretion in urine) by inhibiting the sodium-phosphate cotransporter in the proximal tubule [3, 4]. * **Increased Urine Phosphate (Not Decreased):** Due to the action of PTH on the kidneys, phosphate clearance increases, leading to low serum phosphate levels [2]. 3. **Why Option D is Incorrect:** Decreased ALP is rare and seen in conditions like hypophosphatasia or profound malnutrition, whereas Vitamin D deficiency characteristically shows elevated ALP [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Biochemical Profile of Vitamin D Deficiency:** ↓ Serum Calcium (or normal in early stages) [1], ↓ Serum Phosphate, ↑ PTH, and **↑ Alkaline Phosphatase** [4]. * **Urinary Findings:** Increased phosphate and increased cAMP in urine. * **Radiological Sign:** Look for **Looser’s zones** (pseudofractures) in osteomalacia [4] and **cupping/fraying** of metaphyses in rickets [1]. * **Golden Rule:** In any metabolic bone disease involving high bone turnover (except Multiple Myeloma), ALP is typically elevated.

Question 1272: What is the most common presenting feature of adult hypopituitarism?

A. Hypothyroidism
B. Hypogonadism (Correct Answer)
C. Addison's disease
D. Hyperprolactinemia

Explanation: **Explanation:** In adult hypopituitarism, the loss of pituitary hormones typically follows a progressive and sequential pattern. The gonadotropins (**LH and FSH**) are generally the first to be affected, making **hypogonadism** the most common and often the earliest presenting feature [1]. **1. Why Hypogonadism is Correct:** The pituitary-gonadal axis is highly sensitive to compression or damage [1]. In males, this manifests as decreased libido, erectile dysfunction, and loss of body hair. In females, it presents as amenorrhea, infertility, or dyspareunia [3]. Because these symptoms are often noticeable early in the disease course, they serve as the primary clinical marker for adult hypopituitarism. **2. Analysis of Incorrect Options:** * **Hypothyroidism (TSH deficiency):** While common, TSH is usually lost *after* the loss of Growth Hormone and Gonadotropins [4]. It presents later with fatigue and weight gain. * **Addison’s Disease (ACTH deficiency):** ACTH is typically the last hormone to be lost in progressive pituitary failure [4]. While life-threatening, it is rarely the *initial* presenting feature. * **Hyperprolactinemia:** This occurs in "Stalk Effect" (loss of dopamine inhibition) or prolactinomas. While it causes hypogonadism, it is a specific etiology rather than a universal feature of general hypopituitarism. **3. NEET-PG High-Yield Pearls:** * **Sequence of hormone loss:** "Go Look For Adenoma" → **G**H > **L**H/**F**SH > **T**SH > **A**CTH. * **Most common cause:** Pituitary adenoma (mass effect) [2]. * **Sheehan’s Syndrome:** Postpartum pituitary necrosis; the earliest sign is the failure to lactate (prolactin deficiency). * **Diagnosis:** Insulin Tolerance Test (ITT) is the gold standard for assessing both GH and ACTH reserves.

Question 1273: Which condition is characterized by hypocalcemia with hyperphosphatemia?

A. Chronic Renal Failure (CRF) (Correct Answer)
B. Pseudohypoparathyroidism
C. Vitamin D deficiency
D. Vitamin D deficiency

Explanation: The combination of **hypocalcemia** and **hyperphosphatemia** is a hallmark of conditions where there is either a deficiency/resistance to Parathyroid Hormone (PTH) or a failure of the kidneys to excrete phosphate [1]. **1. Why Chronic Renal Failure (CRF) is correct:** In CRF, the primary mechanism is the decreased glomerular filtration rate (GFR), which leads to **phosphate retention** (hyperphosphatemia) [2]. High phosphate levels directly complex with calcium, lowering serum levels [3]. Additionally, the damaged kidneys fail to convert 25-hydroxyvitamin D into its active form, **1,25-dihydroxyvitamin D (Calcitriol)**, due to 1-alpha-hydroxylase deficiency [1]. This leads to decreased intestinal calcium absorption, further worsening the hypocalcemia [3]. **2. Analysis of Incorrect Options:** * **Pseudohypoparathyroidism:** While this condition *also* presents with hypocalcemia and hyperphosphatemia (due to PTH resistance), **CRF** is the more classic and common clinical scenario for this biochemical profile in standard medical exams unless phenotypic features (Albright’s Hereditary Osteodystrophy) are mentioned [2]. *Note: If this were a "Multiple Select" question, both A and B would be biochemically correct.* * **Vitamin D Deficiency:** This typically leads to **hypocalcemia** and **hypophosphatemia** [2]. Low Vitamin D leads to low calcium, which triggers a secondary rise in PTH. PTH then increases renal phosphate excretion, causing low serum phosphate [1]. **3. NEET-PG High-Yield Pearls:** * **PTH vs. Phosphate:** PTH is a "phosphaturic" hormone (it "Pees out Phosphate"). Therefore, low PTH (Hypoparathyroidism) or PTH resistance (Pseudo-hypoparathyroidism) causes high phosphate [2]. * **Secondary Hyperparathyroidism:** In CRF, the low calcium and high phosphate trigger a compensatory increase in PTH [1]. * **Tertiary Hyperparathyroidism:** Occurs when the parathyroid glands become autonomous after prolonged secondary hyperparathyroidism (usually in end-stage renal disease), leading to **hypercalcemia** [3].

Question 1274: Which condition is characterized by hypocalcemia with hyperphosphatemia?

A. Chronic renal failure (CRF) (Correct Answer)
B. Pseudohypoparathyroidism
C. Vitamin D deficiency
D. Vitamin D deficiency

Explanation: ### Explanation The combination of **hypocalcemia** and **hyperphosphatemia** is a hallmark of conditions where there is either a deficiency of Parathyroid Hormone (PTH), resistance to PTH, or an inability of the kidneys to excrete phosphate [1]. **1. Why Chronic Renal Failure (CRF) is correct:** In CRF, the primary mechanism is the **failure of phosphate excretion** by the kidneys, leading to hyperphosphatemia [1]. High phosphate levels directly complex with calcium, lowering serum levels. Additionally, damaged kidneys cannot convert 25-hydroxyvitamin D into its active form (**1,25-dihydroxyvitamin D**), leading to decreased intestinal calcium absorption. This dual mechanism results in the classic biochemical profile of low calcium and high phosphate [1]. **2. Analysis of Incorrect Options:** * **Pseudohypoparathyroidism:** While this condition *also* presents with hypocalcemia and hyperphosphatemia (due to end-organ resistance to PTH), **CRF is the more common clinical scenario** and the classic answer in this context [1]. However, in many exams, both could be technically correct; in such cases, look for associated features like Albright’s Hereditary Osteodystrophy for Pseudohypoparathyroidism. * **Vitamin D Deficiency:** This leads to **hypocalcemia** and **hypophosphatemia** [1]. Low Vitamin D results in poor absorption of both minerals. Furthermore, the resulting secondary hyperparathyroidism increases renal phosphate excretion, further lowering phosphate levels. **3. NEET-PG High-Yield Pearls:** * **PTH Rule:** PTH normally increases calcium and decreases phosphate ("Phosphate Thrashing Hormone"). Therefore, **Hypoparathyroidism** (low PTH) and **Pseudohypoparathyroidism** (PTH resistance) both cause high phosphate and low calcium [1]. * **CRF Profile:** Low Calcium + High Phosphate + **High PTH** (Secondary Hyperparathyroidism) [1]. * **Vitamin D Deficiency Profile:** Low Calcium + Low Phosphate + High PTH [1]. * **Key Differentiator:** If a question mentions "short 4th/5th metacarpals" and "round facies" with these labs, think **Pseudohypoparathyroidism**.

Question 1275: A patient presents with persistent diarrhea and hypotension. What is the most likely diagnosis?

A. VIPoma (Correct Answer)
B. ACTHoma
C. GRFoma
D. Glucagonoma

Explanation: **Explanation:** The clinical presentation of persistent watery diarrhea and hypotension is classic for a **VIPoma**, a rare neuroendocrine tumor (usually pancreatic) that secretes excessive **Vasoactive Intestinal Peptide (VIP)** [1]. **1. Why VIPoma is correct:** VIP stimulates intestinal secretion of water and electrolytes and inhibits gastric acid secretion [1]. This leads to the **WDHA Syndrome**: * **W**atery **D**iarrhea (secretory, persists even during fasting) * **H**ypokalemia (due to fecal potassium loss) * **A**chlorhydria (suppression of gastric acid) The profound loss of fluids and the potent vasodilatory effect of VIP lead to **hypotension** and dehydration [1]. **2. Why the other options are incorrect:** * **ACTHoma:** Secretes ACTH, leading to Cushing’s syndrome [1]. Typical features include hypertension (not hypotension), central obesity, and hyperglycemia. * **GRFoma:** Secretes Growth Hormone-Releasing Factor, leading to Acromegaly. It does not typically cause acute diarrhea or hypotension. * **Glucagonoma:** Characterized by the "4 Ds": Diabetes, Dermatitis (Necrolytic Migratory Erythema), DVT, and Depression. Diarrhea is less common, and it does not cause hypotension. **3. NEET-PG High-Yield Pearls:** * **Alternative Name:** VIPoma is also known as **Verner-Morrison Syndrome** or **Pancreatic Cholera**. * **Diagnosis:** Elevated fasting serum VIP levels (>200 pg/mL). * **Localization:** Most are found in the tail of the pancreas; 50-70% are metastatic at diagnosis [1]. * **Management:** Initial stabilization requires aggressive fluid resuscitation and **Octreotide** (somatostatin analog) to inhibit VIP release.

Question 1276: Hyperglycemia is seen in all of the following conditions except?

A. Cirrhosis
B. Myotonic dystrophy
C. Lipodystrophy
D. Sarcoma (Correct Answer)

Explanation: **Explanation:** The correct answer is **Sarcoma**. While most endocrine and metabolic disorders lead to hyperglycemia, certain non-pancreatic tumors, particularly **large mesenchymal tumors (Sarcomas)**, are classic causes of **fasting hypoglycemia** [2]. **1. Why Sarcoma is the correct answer:** Large sarcomas (e.g., retroperitoneal fibrosarcoma) cause hypoglycemia through a paraneoplastic syndrome known as **Doege-Potter Syndrome**. These tumors overproduce **"Big" IGF-II** (Insulin-like Growth Factor II), which binds to insulin receptors and increases glucose utilization while inhibiting hepatic glucose production. **2. Why the other options are incorrect:** * **Cirrhosis:** Chronic liver disease often leads to "Hepatogenous Diabetes." This occurs due to peripheral insulin resistance, portosystemic shunting (reducing first-pass metabolism of insulin), and impaired glycogenesis. * **Myotonic Dystrophy:** This condition is characteristically associated with **insulin resistance**. Patients often exhibit hyperinsulinemia and impaired glucose tolerance, leading to hyperglycemia. * **Lipodystrophy:** Whether congenital or acquired, the loss of functional adipose tissue leads to severe insulin resistance, ectopic fat deposition (in liver and muscle), and decreased adiponectin levels, resulting in refractory hyperglycemia and diabetes. **Clinical Pearls for NEET-PG:** * **Non-Islet Cell Tumor Hypoglycemia (NICTH):** Always suspect this in a patient with a large abdominal mass and low blood sugar. The biochemical hallmark is low blood glucose, low insulin, and low C-peptide, but **elevated IGF-II** levels [2]. * **Other causes of Hyperglycemia:** Acromegaly, Cushing’s syndrome, Pheochromocytoma, and Glucagonoma [1]. * **High-Yield Fact:** Myotonic dystrophy is the most common adult-onset muscular dystrophy and is a classic multisystem disorder involving the endocrine system (diabetes, testicular atrophy).

Question 1277: All of the following are seen in Growth Hormone (GH) deficiency except?

A. Hyperglycemia (Correct Answer)
B. Stunting
C. Delayed bone age
D. High pitched voice

Explanation: Growth Hormone (GH) is a potent **anabolic [1] and counter-regulatory hormone**. Its primary metabolic function is to antagonize the effects of insulin, thereby increasing blood glucose levels. **1. Why Hyperglycemia is the correct answer:** GH deficiency leads to a lack of insulin-antagonistic activity. Instead of hyperglycemia, patients typically present with **hypoglycemia** (especially fasting hypoglycemia in children). GH promotes gluconeogenesis and reduces peripheral glucose uptake; without it, blood sugar levels drop. Therefore, hyperglycemia is not a feature of GH deficiency. **2. Analysis of other options:** * **Stunting (B):** GH is essential for linear growth via the production of IGF-1. Deficiency results in proportionate short stature or stunting. * **Delayed bone age (C):** In GH deficiency, skeletal maturation is significantly slowed. The bone age is typically delayed compared to the chronological age. * **High-pitched voice (D):** This occurs due to the underdevelopment of the larynx and facial bones (midfacial hypoplasia), leading to a characteristic "doll-like" appearance and a high-pitched, squeaky voice. **Clinical Pearls for NEET-PG:** * **Laron Syndrome:** A condition of GH insensitivity (mutated GH receptor) characterized by **high GH levels but low IGF-1 levels**. * **Micropenis:** A classic sign of congenital GH deficiency in male neonates, often accompanied by hypoglycemia. * **Diagnosis:** The gold standard is a **GH stimulation test** (using insulin, glucagon, or arginine). A single random GH measurement is useless due to its pulsatile secretion. * **Treatment:** Recombinant Human GH (Somatropin).

Question 1278: What is the storage form of thyroid hormone?

A. Tri-iodotyrosine
B. Tri-iodothyronine
C. Thyroglobulin (Correct Answer)
D. Di-iodotyrosine

Explanation: The thyroid gland is unique among endocrine glands because it stores its hormones extracellularly in the follicular lumen [1]. The correct answer is **Thyroglobulin (Tg)**, a large glycoprotein synthesized by follicular cells [1]. 1. **Why Thyroglobulin is correct:** After synthesis, Tg is secreted into the colloid. Within this colloid, iodine is attached to tyrosine residues on the Tg backbone (organification) to form MIT and DIT, which then couple to form T3 and T4 [2]. These hormones remain covalently bound to the thyroglobulin molecule, acting as a reservoir that can provide a 2–3 month supply of thyroid hormone [1]. 2. **Why other options are incorrect:** * **Tri-iodothyronine (T3):** This is the metabolically active form of the hormone, not the storage form. It is released into the blood after the proteolysis of thyroglobulin [1]. * **Tri-iodotyrosine:** This is a distractor term; it is not a standard intermediate in thyroid physiology. * **Di-iodotyrosine (DIT):** This is an intermediate precursor formed during the organification of iodine. While it is stored as part of the thyroglobulin complex, it is not the "storage form" itself but rather a building block [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Wolff-Chaikoff Effect:** A transient decrease in thyroid hormone synthesis due to the ingestion of a large amount of iodine. * **Pendred Syndrome:** Characterized by sensorineural hearing loss and goiter due to a defect in the Pendrin iodine transporter. * *Thyroglobulin Levels:** Used clinically as a **tumor marker** to monitor for recurrence in patients with differentiated thyroid cancer (Papillary or Follicular) after total thyroidectomy.

Question 1279: Which of the following is a sign of diabetic ketoacidosis?

A. Loss of sweating
B. Depression
C. Dehydration (Correct Answer)
D. Absent deep tendon reflexes

Explanation: ### Explanation **Correct Answer: C. Dehydration** **Pathophysiology:** Diabetic Ketoacidosis (DKA) is characterized by the triad of hyperglycemia, ketosis, and metabolic acidosis. The primary driver of dehydration in DKA is **osmotic diuresis**. High blood glucose levels exceed the renal threshold for reabsorption, leading to glucose excretion in the urine. This exerts an osmotic pull, dragging water and electrolytes (sodium, potassium) with it. Furthermore, vomiting (common in DKA) and insensible losses due to **Kussmaul breathing** (rapid, deep respirations) further exacerbate the fluid deficit. An average adult in DKA may have a fluid deficit of 6–10 liters. **Analysis of Incorrect Options:** * **A. Loss of sweating:** This is not a classic sign of DKA. While severe dehydration can lead to dry skin and mucous membranes, "loss of sweating" (anhidrosis) is more characteristic of heat stroke or autonomic neuropathy. * **B. Depression:** While DKA causes altered mental status, it typically presents as lethargy, confusion, or coma (due to hyperosmolality and acidosis) rather than clinical depression. * **C. Absent deep tendon reflexes:** This is not a feature of DKA. However, it can be seen in severe **hypokalemia** (which may occur during insulin therapy if not monitored) or magnesium toxicity. **NEET-PG High-Yield Pearls:** * **Kussmaul Breathing:** A compensatory mechanism to blow off $CO_2$ to counter metabolic acidosis. * **Fruit Odor:** Caused by the exhalation of **acetone**. * **Abdominal Pain:** DKA often presents with "pseudo-peritonitis" (severe abdominal pain and guarding), which resolves with metabolic correction. * **Management Priority:** The first step in management is always **aggressive fluid resuscitation** (Normal Saline), followed by intravenous insulin and potassium replacement. * **Anion Gap:** DKA is a classic cause of **High Anion Gap Metabolic Acidosis (HAGMA)**.

Question 1280: A female child presents with virilization and hypertension with low plasma renin. What is the most likely diagnosis?

A. 21α hydroxylase deficiency
B. 11 β hydroxylase deficiency (Correct Answer)
C. 3β hydroxylase deficiency
D. Conn’s syndrome

Explanation: ### Explanation The clinical presentation of **virilization** (excess androgens) combined with **hypertension** (mineralocorticoid effect) and **low renin** is the classic triad for **11β-hydroxylase deficiency**. [1] #### Why Option B is Correct: In 11β-hydroxylase deficiency, the conversion of 11-deoxycorticosterone (DOC) to corticosterone and 11-deoxycortisol to cortisol is blocked. This leads to: 1. **Shunting to Androgens:** Excess precursor accumulation is diverted toward the androgen pathway, causing virilization (ambiguous genitalia in females, precocious puberty in males). [1] 2. **Mineralocorticoid Excess:** There is a massive buildup of **11-deoxycorticosterone (DOC)**. DOC is a potent mineralocorticoid that causes sodium retention and volume expansion, leading to **hypertension** and feedback suppression of **plasma renin**. [1] #### Why Other Options are Incorrect: * **A. 21α hydroxylase deficiency:** This is the most common CAH. While it causes virilization, it results in **hypotension** and salt-wasting (due to lack of mineralocorticoids) and **high renin**. [2] * **C. 3β hydroxylase deficiency:** This rare form results in a lack of all three classes of adrenal steroids. It typically presents with salt-wasting and incomplete virilization/ambiguous genitalia in both sexes. * **D. Conn’s syndrome:** While this causes hypertension and low renin (primary hyperaldosteronism), it does **not** cause virilization or androgen excess. #### High-Yield Clinical Pearls for NEET-PG: * **The "Rule of 1s":** If the enzyme starts with **1** (11β-hydroxylase, 17α-hydroxylase), it causes **Hypertension**. * **Virilization vs. Hypertension:** * **21α-OH:** Virilization + Hypotension (Salt-wasting). * **11β-OH:** Virilization + Hypertension. * **17α-OH:** No Virilization (Sexual infantilism) + Hypertension. * **Diagnostic Marker:** Elevated levels of **11-deoxycortisol** and **11-deoxycorticosterone** in the blood.

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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