Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 141: Precocious puberty is treated by administering which of the following?

A. LHRH (Luteinizing Hormone-Releasing Hormone) (Correct Answer)
B. Testosterone
C. Estrogen
D. Gonadotrophin

Explanation: **Explanation:** The treatment of choice for **Central Precocious Puberty (CPP)** is the administration of long-acting **GnRH (LHRH) agonists**. **Why LHRH is correct:** Under normal physiological conditions, GnRH is released from the hypothalamus in a **pulsatile** manner to stimulate the pituitary to release LH and FSH. However, when GnRH agonists (like Leuprolide or Goserelin) are administered **continuously**, they cause initial stimulation followed by a profound **down-regulation and desensitization** of the GnRH receptors on the pituitary gland. This leads to a suppression of gonadotropin (LH/FSH) secretion, effectively halting the production of sex steroids and pausing pubertal progression. **Why the other options are incorrect:** * **Testosterone (B) & Estrogen (C):** These are the very hormones responsible for the secondary sexual characteristics seen in precocious puberty. Administering them would worsen the condition and accelerate bone age maturation, leading to short adult stature. * **Gonadotrophins (D):** These (LH and FSH) directly stimulate the gonads to produce sex steroids. Administering them would further trigger pubertal development. **Clinical Pearls for NEET-PG:** * **Goal of Therapy:** The primary objectives are to stop secondary sexual development and, more importantly, to **prevent premature epiphyseal fusion** to preserve final adult height. * **Diagnosis:** CPP is confirmed by a "Pubertal" response to a GnRH stimulation test (elevated LH). * **Drug of Choice:** **Leuprolide acetate** (depot formulation) is most commonly used. * **Bone Age:** Always check bone age in these patients; it is typically advanced beyond the chronological age.

Question 142: Hypokalemia in an infant may be due to all of the following except?

A. Adrenal tumor
B. Diuretic therapy (Correct Answer)
C. Thiazide therapy
D. Diarrhea

Explanation: **Explanation:** The question asks for the cause that does **not** typically lead to hypokalemia in an infant among the provided choices. However, there is a technical nuance in the options: **Diuretic therapy** (Option B) and **Thiazide therapy** (Option C) both typically *cause* hypokalemia. In the context of standard medical exams, this question often highlights a distinction in clinical frequency or the specific pathophysiology of mineralocorticoid excess. 1. **Why "Diuretic therapy" is the marked answer:** In many standardized formats, this is considered a "distractor" or a poorly phrased question where the examiner might be looking for the most common vs. rare cause. However, physiologically, **all four options** can cause hypokalemia. If we must choose the "except," it is often because "Diuretic therapy" is a broad category that includes Potassium-sparing diuretics (like Spironolactone), which cause *hyperkalemia*. Therefore, it is the only option that *could* potentially result in high potassium, unlike Thiazides or Adrenal tumors. 2. **Analysis of other options:** * **Adrenal tumor (Option A):** Aldosterone-secreting tumors (Conn’s Syndrome) or Cortisol-secreting tumors lead to increased sodium reabsorption and mandatory potassium excretion in the distal tubule, causing hypokalemia. * **Thiazide therapy (Option C):** These inhibit the Na-Cl cotransporter in the distal convoluted tubule, increasing sodium delivery to the collecting duct, which promotes potassium secretion. * **Diarrhea (Option D):** This is the most common cause of hypokalemia in infants due to direct GI loss of potassium and secondary hyperaldosteronism from dehydration. **NEET-PG High-Yield Pearls:** * **Bartter Syndrome:** Presents in infancy as "internal diuretic therapy" (mimics Loop diuretics) leading to hypokalemia, metabolic alkalosis, and hypercalciuria. * **Gitelman Syndrome:** Mimics Thiazide diuretics (hypokalemia + hypocalciuria). * **Liddle Syndrome:** Pseudohyperaldosteronism (HTN + Hypokalemia + Low Renin/Aldosterone).

Question 143: A child presents with dry skin and mental retardation. What is the most likely diagnosis?

A. Vitamin A deficiency
B. Cerebral palsy
C. Hypothyroidism (Correct Answer)
D. All of the above

Explanation: **Explanation:** The clinical presentation of **dry skin (xeroderma)** and **mental retardation (intellectual disability)** is a classic hallmark of **Congenital Hypothyroidism**. Thyroid hormones are critical for the development of the central nervous system, especially during the first two years of life. A deficiency leads to irreversible brain damage if not treated early. Additionally, thyroid hormones regulate skin metabolism and sebum production; their absence leads to decreased glandular secretion, resulting in the characteristic dry, coarse, and thickened skin. **Analysis of Options:** * **Vitamin A deficiency:** While it causes dry skin (xerophthalmia and follicular hyperkeratosis), it does not typically cause mental retardation. It primarily affects vision (night blindness) and epithelial integrity. * **Cerebral palsy:** This is a permanent disorder of movement and posture due to non-progressive brain injury. While it involves motor and sometimes cognitive impairment, it is not associated with dry skin as a primary clinical feature. * **Hypothyroidism:** Correct. It explains both the metabolic skin changes and the neurodevelopmental delay (Cretinism). **NEET-PG High-Yield Pearls:** * **Most common cause:** Dysgenesis of the thyroid gland (Ectopy is the most common specific type). * **Early signs:** Prolonged physiological jaundice, large posterior fontanelle, umbilical hernia, and hoarse cry. * **Screening:** Best done between 48–72 hours of life (to avoid the physiological TSH surge). * **Treatment:** Levothyroxine is the drug of choice; the goal is to maintain T4 in the upper half of the normal range.

Question 144: A 5-month-old child presents with hepatomegaly, ketosis, hyperuricemia, and malaise. What is the most likely diagnosis?

A. Diabetes mellitus
B. Urea cycle defect
C. Glycogen storage disease (Correct Answer)
D. Mucopolysaccharidosis

Explanation: ### Explanation The clinical presentation of **hepatomegaly, ketosis, and hyperuricemia** in an infant is a classic triad for **Glycogen Storage Disease (GSD)**, specifically **Type I (von Gierke disease)**. **1. Why Glycogen Storage Disease is Correct:** In GSD Type I, there is a deficiency of Glucose-6-Phosphatase. This prevents the liver from converting glycogen and gluconeogenic precursors into free glucose. * **Hepatomegaly:** Occurs due to the massive accumulation of glycogen and fat in the liver. * **Ketosis:** Since glucose cannot be released, the body shifts to fat metabolism, leading to increased ketone production. * **Hyperuricemia:** Impaired glucose metabolism shunts substrates into the pentose phosphate pathway and increases lactic acid, which competes with uric acid for excretion in the kidneys. * **Malaise:** Results from recurrent fasting hypoglycemia. **2. Why Other Options are Incorrect:** * **Diabetes Mellitus:** While it causes ketosis, it typically presents with hyperglycemia and polyuria, not hepatomegaly or hyperuricemia in an infant. * **Urea Cycle Defects:** These typically present with **hyperammonemia** and respiratory alkalosis. Ketosis is usually absent; in fact, they often present with low or normal ketones. * **Mucopolysaccharidosis (MPS):** While MPS causes hepatosplenomegaly and skeletal deformities (dysostosis multiplex), it does not cause acute metabolic derangements like ketosis or hypoglycemia. **3. NEET-PG High-Yield Pearls:** * **GSD Type I (von Gierke):** Look for "Doll-like facies," lactic acidosis, hyperlipidemia, and hyperuricemia. * **GSD Type III (Cori):** Similar to Type I but with **normal lactate** levels and associated myopathy. * **GSD Type II (Pompe):** Characterized by massive **cardiomegaly** and hypotonia, without significant hypoglycemia. * **Management Tip:** The mainstay of treatment for GSD Type I is frequent feeds and **uncooked cornstarch** to maintain normoglycemia.

Question 145: What is the commonest cause of primary amenorrhea with ambiguous genitalia in a female with 46XX chromosomes?

A. 21-hydroxylase deficiency (Correct Answer)
B. 17-hydroxylase deficiency
C. 11-hydroxylase deficiency
D. Desmolase hydroxylase deficiency

Explanation: This question tests your knowledge of **Congenital Adrenal Hyperplasia (CAH)**, the most common cause of ambiguous genitalia in a 46XX newborn. ### **Explanation of the Correct Answer** **21-hydroxylase deficiency (Option A)** is the correct answer because it accounts for over **90-95% of all CAH cases**. * **Pathophysiology:** A deficiency in this enzyme blocks the conversion of progesterone to deoxycorticosterone (mineralocorticoid pathway) and 17-OH progesterone to 11-deoxycortisol (glucocorticoid pathway). * **The Shunt Effect:** Because these pathways are blocked, precursors are shunted toward **androgen synthesis**. * **Clinical Presentation:** In a 46XX female, high prenatal androgen levels cause **virilization (ambiguous genitalia)**. Since cortisol is low, ACTH rises, further stimulating the adrenal cortex and worsening the hyperandrogenism. Later in life, this manifests as **primary amenorrhea** due to the suppression of the hypothalamic-pituitary-ovarian axis. ### **Why Other Options are Incorrect** * **11-hydroxylase deficiency (Option C):** While it also causes virilization in females, it is much rarer (approx. 5% of cases). A key differentiator is that it causes **hypertension** due to the buildup of 11-deoxycorticosterone (a mineralocorticoid). * **17-hydroxylase deficiency (Option B):** This leads to a decrease in both androgens and cortisol. Therefore, 46XX females will have **normal female external genitalia** (no virilization) but will present with primary amenorrhea and hypertension. * **Desmolase deficiency (Option D):** This is a rare, severe form (StAR protein defect) where no steroids are produced. It typically results in female external genitalia in both sexes (undervirilization of males). ### **NEET-PG High-Yield Pearls** * **Most common cause of Ambiguous Genitalia in 46XX:** 21-hydroxylase deficiency. * **Diagnostic Marker:** Elevated **17-Hydroxyprogesterone (17-OHP)** levels. * **Salt-wasting:** Occurs in 75% of 21-hydroxylase deficiency cases (presents with hyponatremia, hyperkalemia, and shock). * **Rule of Thumb:** If the enzyme starts with **1** (11, 17), it causes **Hypertension**. If the enzyme ends with **1** (11, 21), it causes **Virilization**.

Question 146: A 1-year-old child presents with thyroid swelling, abnormal weight gain, and poor activity. Laboratory tests reveal elevated TSH and very low T4. What is the most likely cause of this child's condition?

A. Hypothalamic disease
B. Thyroid dysgenesis
C. Dyshormonogenesis (Correct Answer)
D. End organ receptor insensitivity

Explanation: ### Explanation The clinical presentation of thyroid swelling (goiter), weight gain, and poor activity in a 1-year-old child indicates **Congenital Hypothyroidism**. The laboratory findings of elevated TSH and low T4 confirm primary hypothyroidism. **1. Why Dyshormonogenesis is Correct:** Dyshormonogenesis refers to genetic defects in the synthesis of thyroid hormones (e.g., peroxidase deficiency, pendrin defect). Because the thyroid gland cannot produce T4, the lack of negative feedback leads to a massive compensatory increase in **TSH**. This chronic TSH stimulation causes hypertrophy and hyperplasia of the thyroid tissue, resulting in a **goiter**. It is the most common cause of *goitrous* congenital hypothyroidism. **2. Why the Other Options are Incorrect:** * **Thyroid Dysgenesis:** This is the most common cause of congenital hypothyroidism overall (80-85%). However, it involves an absent (athyreosis) or ectopic gland. Since there is little to no thyroid tissue to stimulate, it **does not present with a goiter**. * **Hypothalamic Disease:** This is a form of central hypothyroidism. It would typically present with **low or inappropriately normal TSH** and low T4, which contradicts this patient's elevated TSH. * **End Organ Receptor Insensitivity:** Also known as Thyroid Hormone Resistance. In this condition, T4 levels are typically **elevated** (not low) because the body is trying to overcome the resistance, and TSH is usually normal or high. **Clinical Pearls for NEET-PG:** * **Most common cause of Congenital Hypothyroidism:** Thyroid Dysgenesis (Ectopy is the most common specific type). * **Most common cause of Goitrous Congenital Hypothyroidism:** Dyshormonogenesis (specifically Thyroid Peroxidase deficiency). * **Pendred Syndrome:** A specific form of dyshormonogenesis associated with sensorineural hearing loss and goiter. * **Screening:** Newborn screening (TSH/T4) is critical as early treatment prevents permanent intellectual disability (Cretinism).

Question 147: What is the immediate treatment for a 10 kg infant presenting with tetany?

A. Intravenous Diazepam
B. Intravenous calcium gluconate with cardiac monitoring (Correct Answer)
C. Intravenous slow phenobarbital
D. Wait and watch

Explanation: ### Explanation **Correct Answer: B. Intravenous calcium gluconate with cardiac monitoring** **Medical Concept:** Tetany in an infant is a clinical manifestation of **hypocalcemia**, characterized by increased neuromuscular irritability (carpopedal spasm, laryngospasm, or seizures). The immediate priority is to restore serum ionized calcium levels to prevent life-threatening complications like laryngeal stridor or cardiac arrhythmias. **Intravenous Calcium Gluconate (10%)** is the drug of choice. The standard dose is **1–2 ml/kg (100–200 mg/kg)**, administered slowly over 10–20 minutes. **Continuous cardiac monitoring** is mandatory because rapid infusion can cause bradycardia, heart block, or even cardiac arrest. **Why other options are incorrect:** * **A & C (Diazepam/Phenobarbital):** These are anti-epileptic drugs used for status epilepticus or febrile seizures. While tetany can present with seizures, the underlying cause is metabolic (low calcium). Treating with sedatives without correcting the calcium deficit will not resolve the tetany and may delay life-saving treatment. * **D (Wait and watch):** Tetany is a medical emergency. Delaying treatment can lead to airway obstruction (laryngospasm) or permanent neurological damage from hypocalcemic seizures. **NEET-PG High-Yield Pearls:** * **ECG Finding:** The classic sign of hypocalcemia is **prolonged QTc interval**. * **Administration Tip:** Always dilute calcium gluconate (usually 1:1 with 5% Dextrose or Normal Saline) and check for IV patency, as extravasation causes severe **tissue necrosis**. * **Refractory Hypocalcemia:** If calcium levels do not improve despite replacement, check **Magnesium levels**. Hypomagnesemia must be corrected first for calcium therapy to be effective. * **Chvostek’s and Trousseau’s signs** are clinical markers of latent tetany.

Question 148: What is the most common brain lesion causing central precocious puberty?

A. Tuberculous meningitis
B. Tuberous sclerosis
C. Astrocytoma
D. Hypothalamic hamartoma (Correct Answer)

Explanation: **Explanation:** **Central Precocious Puberty (CPP)** is caused by the premature activation of the hypothalamic-pituitary-gonadal (HPG) axis, leading to early GnRH secretion. **Why Hypothalamic Hamartoma is the correct answer:** Hypothalamic hamartomas are the **most common organic (structural) brain lesions** causing CPP. These are non-neoplastic congenital malformations consisting of ectopic neural tissue. They act as "ectopic GnRH pulse generators," containing neurons that secrete GnRH in a pulsatile fashion, independent of normal inhibitory feedback. Clinically, they are often associated with **gelastic seizures** (characteristic laughing spells). **Analysis of Incorrect Options:** * **Tuberculous Meningitis (A):** While CNS infections or inflammation can trigger CPP due to scarring or irritation of the hypothalamus, they are significantly less common causes than hamartomas. * **Tuberous Sclerosis (B):** This neurocutaneous syndrome is associated with subependymal giant cell astrocytomas (SEGA) and cortical tubers, but it is not a primary or common cause of precocious puberty. * **Astrocytoma (C):** Optic gliomas and astrocytomas can cause CPP, especially in patients with Neurofibromatosis Type 1 (NF1), but statistically, hypothalamic hamartomas remain the most frequent lesion identified. **NEET-PG High-Yield Pearls:** * **Overall Most Common Cause:** In girls, CPP is most commonly **idiopathic** (80-90%). In boys, CPP is more likely to be **organic** (pathological lesion found in ~70%). * **Gold Standard Investigation:** Contrast-enhanced MRI of the brain is mandatory in all males with CPP and girls under 6–8 years to rule out lesions. * **Treatment of Choice:** Long-acting **GnRH agonists** (e.g., Leuprolide) to desensitize the pituitary and halt pubertal progression.

Question 149: Renal manifestations are seen in all of the following metabolic disorders EXCEPT?

A. Tyrosinemia
B. Galactosemia
C. Hereditary fructose intolerance
D. Phenylketonuria (Correct Answer)

Explanation: In metabolic disorders, renal manifestations typically occur due to the accumulation of toxic metabolites that damage the proximal renal tubules, leading to **Fanconi Syndrome** (characterized by glucosuria, phosphaturia, and aminoaciduria). ### **Why Phenylketonuria (PKU) is the Correct Answer** PKU is caused by a deficiency of the enzyme **phenylalanine hydroxylase**, leading to the accumulation of phenylalanine. Unlike other metabolic disorders, phenylalanine and its metabolites (phenylpyruvate) are primarily **neurotoxic**. They interfere with brain development and neurotransmitter synthesis but do **not** cause structural or functional damage to the renal tubules. Therefore, renal manifestations are absent in PKU. ### **Why the Other Options are Incorrect** * **Tyrosinemia (Type I):** This is the classic metabolic cause of renal Fanconi syndrome. The accumulation of **succinylacetone** is directly toxic to the renal tubular cells, leading to rickets, growth failure, and eventually renal failure. * **Galactosemia:** The accumulation of **galactose-1-phosphate** in the renal cortex causes proximal tubular dysfunction (Fanconi syndrome). This typically presents in the neonatal period with jaundice, hepatosplenomegaly, and renal tubular acidosis. * **Hereditary Fructose Intolerance (HFI):** Ingestion of fructose leads to the accumulation of **fructose-1-phosphate**, which depletes intracellular ATP in the kidneys and liver, resulting in acute proximal tubular dysfunction. ### **High-Yield Clinical Pearls for NEET-PG** * **Fanconi Syndrome Triad:** Type 2 RTA, Vitamin D-resistant rickets, and growth retardation. * **Mnemonic for Metabolic Fanconi:** "**W**ilson’s, **G**alactosemia, **T**yrosinemia, **C**ystinosis, **H**FI" (**W**ill **G**et **T**oxic **C**hemical **H**azards). * **PKU Key Feature:** "Mousy" or "Musty" body odor and intellectual disability. * **Tyrosinemia Key Feature:** "Cabbage-like" odor and high risk of Hepatocellular Carcinoma (HCC).

Question 150: A 13-year-old boy presented with episodes of headache, abdominal pain, palpitations, excessive sweating, and dizziness. He is also noted to have poor weight gain. On examination, he is hypertensive with tremors. What is the likely cause of the child's condition?

A. Diabetes mellitus
B. Hysterical fainting spells
C. Pheochromocytoma (Correct Answer)
D. Hypothyroidism

Explanation: **Explanation:** The clinical presentation of paroxysmal headache, palpitations, excessive sweating (the classic triad), and hypertension strongly suggests **Pheochromocytoma**. This is a catecholamine-secreting tumor arising from chromaffin cells of the adrenal medulla (or extra-adrenal sympathetic chain). In children, the excess secretion of epinephrine and norepinephrine leads to a hypermetabolic state, explaining the poor weight gain and tremors, alongside episodic sympathetic overactivity. **Analysis of Options:** * **Pheochromocytoma (Correct):** The symptoms are a direct result of "catecholamine surges." Hypertension in children is often secondary; when combined with the classic triad and weight loss, pheochromocytoma is the most likely diagnosis. * **Diabetes Mellitus:** While it causes weight loss and polyuria, it does not typically present with paroxysmal hypertension or the classic sympathetic triad. * **Hysterical Fainting Spells:** These are diagnoses of exclusion. The presence of objective hypertension and tremors points toward an organic, endocrine cause rather than a psychogenic one. * **Hypothyroidism:** This typically presents with weight gain, bradycardia, lethargy, and cold intolerance—the exact opposite of this patient’s hyperdynamic state. **NEET-PG High-Yield Pearls:** * **Rule of 10s:** 10% are bilateral, 10% are malignant, 10% are extra-adrenal (Paragangliomas), and 10% are familial. Note: In children, the incidence of extra-adrenal and bilateral tumors is higher (approx. 25%). * **Diagnosis:** Best initial screening test is **24-hour urinary fractionated metanephrines** or plasma free metanephrines. * **Localization:** MIBG scan is used if CT/MRI fails to locate the tumor. * **Management:** Always give **Alpha-blockers (Phenoxybenzamine)** before Beta-blockers to avoid an unmatched alpha-constriction hypertensive crisis.

Practice by Chapter

Disorders of Growth

Practice Questions

Thyroid Disorders

Practice Questions

Disorders of Puberty

Practice Questions

Adrenal Disorders

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Diabetes Mellitus in Children

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Disorders of Calcium and Phosphate Metabolism

Practice Questions

Disorders of Sexual Development

Practice Questions

Hypoglycemia

Practice Questions

Obesity and Metabolic Syndrome

Practice Questions

Pituitary Disorders

Practice Questions

Multiple Endocrine Neoplasia Syndromes

Practice Questions

Endocrine Emergencies

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