Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 151: Which disorder is associated with convulsions, cataract, and mental retardation?

A. Galactosaemia (Correct Answer)
B. Phenylketonuria
C. Tyrosinemia
D. Maple syrup disease

Explanation: **Explanation:** **Classic Galactosemia** is an autosomal recessive disorder caused by a deficiency of the enzyme **Galactose-1-phosphate uridyltransferase (GALT)**. The accumulation of galactose and its metabolites (galactose-1-phosphate and galactitol) leads to multi-organ damage: * **Cataract:** Galactitol accumulates in the lens, causing osmotic swelling and "oil-drop" cataracts. * **Convulsions & Mental Retardation:** Accumulation of toxic metabolites in the brain leads to cerebral edema, seizures, and progressive intellectual disability if untreated. * **Other features:** Jaundice, hepatosplenomegaly, and a high risk of *E. coli* sepsis. **Why other options are incorrect:** * **Phenylketonuria (PKU):** Characterized by intellectual disability, seizures, and a "mousy" odor, but **cataracts are not a feature**. Patients typically have fair skin and blue eyes due to melanin deficiency. * **Tyrosinemia (Type 1):** Primarily presents with severe liver failure, renal tubular dysfunction (Fanconi syndrome), and a "cabbage-like" odor. It does not typically cause cataracts. * **Maple Syrup Urine Disease (MSUD):** Presents early with poor feeding, vomiting, and a "maple syrup" odor in urine. While it causes severe neurological distress and seizures, it is not associated with cataracts. **High-Yield Clinical Pearls for NEET-PG:** * **Screening:** Reducing substances in urine (Benedict's test positive) but a negative dipstick for glucose is a classic diagnostic clue. * **Cataract Type:** Described as **"Oil-drop" cataract**. * **Management:** Immediate exclusion of lactose and galactose from the diet (switching to soy-based formula). * **Complication:** Even with treatment, many patients develop speech deficits and females often face **premature ovarian failure**.

Question 152: Lesions of which of the hypothalamic nuclei cause diabetes insipidus?

A. Dorsomedial nuclei
B. Supraoptic and paraventricular nuclei (Correct Answer)
C. Median preoptic nuclei
D. Ventromedial nuclei

Explanation: **Explanation:** **Diabetes Insipidus (DI)** is characterized by the inability to concentrate urine due to either a deficiency of Antidiuretic Hormone (ADH/Vasopressin) or resistance to its action. **Why Option B is Correct:** ADH is synthesized primarily in the cell bodies of the **Supraoptic nuclei (SON)** and **Paraventricular nuclei (PVN)** of the hypothalamus. Once synthesized, it travels via the hypothalamo-hypophyseal tract to the posterior pituitary, where it is stored and released. Lesions involving these nuclei or the proximal part of the pituitary stalk disrupt ADH production, leading to **Central Diabetes Insipidus**. **Why the Other Options are Incorrect:** * **A. Dorsomedial nuclei:** Primarily involved in emotional behavior and circadian regulation of feeding and drinking. * **C. Median preoptic nuclei:** Involved in thermoregulation and the generation of thirst; while related to fluid intake, they do not synthesize ADH. * **D. Ventromedial nuclei:** Known as the **"Satiety Center."** Lesions here lead to hyperphagia and obesity. **High-Yield Clinical Pearls for NEET-PG:** * **Synthesis vs. Storage:** ADH is *produced* in the hypothalamus (SON > PVN) but *stored* in the posterior pituitary (Neurohypophysis). * **The "Thirst Center":** Located in the lateral hypothalamus. * **Triphasic Response:** Post-neurosurgery, patients may show a transient DI, followed by a period of SIADH (due to leaking of stored ADH), and finally permanent DI. * **Diagnosis:** The **Water Deprivation Test** is the gold standard. Central DI shows a >50% increase in urine osmolality after Desmopressin administration, whereas Nephrogenic DI shows little to no response.

Question 153: A child presented with clinical features of rickets but low level of serum alkaline phosphatase. What is the most likely diagnosis?

A. Primary biliary cirrhosis
B. Hypophosphatasia (Correct Answer)
C. Hyperparathyroidism
D. Benign familial hyperphosphatasemia

Explanation: **Explanation:** The hallmark of almost all forms of rickets (nutritional or genetic) is an **elevated serum Alkaline Phosphatase (ALP)**, which reflects increased osteoblastic activity. The presence of rachitic clinical features (e.g., bow legs, rachitic rosary) paired with a **low serum ALP** is pathognomonic for **Hypophosphatasia**. **1. Why Hypophosphatasia is correct:** Hypophosphatasia is a rare genetic disorder caused by a mutation in the *ALPL* gene, leading to a deficiency of the **Tissue Non-Specific Alkaline Phosphatase (TNSALP)** enzyme. This enzyme is crucial for mineralizing osteoid. Its deficiency leads to the accumulation of inorganic pyrophosphate (a potent inhibitor of mineralization), resulting in rickets-like skeletal deformities and premature loss of deciduous teeth. **2. Why the other options are incorrect:** * **Primary Biliary Cirrhosis:** This is a cholestatic liver disease. Cholestasis typically causes a significant **increase** in ALP due to impaired bile flow. * **Hyperparathyroidism:** High levels of Parathyroid Hormone (PTH) increase bone turnover, which typically leads to **elevated** ALP levels. * **Benign Familial Hyperphosphatasemia:** As the name suggests, this is characterized by persistently **high** levels of serum ALP in asymptomatic individuals, with no evidence of bone or liver disease. **NEET-PG High-Yield Pearls:** * **Biochemical Triad of Hypophosphatasia:** Low serum ALP, elevated urinary phosphoethanolamine, and elevated serum pyridoxal-5-phosphate (Vitamin B6). * **Clinical Clue:** Early loss of primary teeth (incisors) with the root intact is a classic sign. * **Differential for Low ALP:** Hypophosphatasia, severe hypothyroidism (cretinism), scurvy, severe magnesium deficiency, and zinc deficiency.

Question 154: Which of the following are features of Laurence-Moon-Biedl syndrome?

A. Hypogonadism
B. Obesity
C. Polydactyly
D. All of the above (Correct Answer)

Explanation: **Explanation:** **Laurence-Moon-Bardet-Biedl Syndrome (LMBBS)** is a rare, autosomal recessive ciliopathy characterized by multi-organ involvement. The correct answer is **"All of the above"** because the syndrome is classically defined by a pentad of clinical features resulting from dysfunctional primary cilia. 1. **Obesity:** This is a hallmark feature, typically central in distribution and appearing in early childhood. 2. **Hypogonadism:** Patients often present with delayed puberty, small genitalia (micropenis), or primary gonadal failure. 3. **Polydactyly:** Post-axial polydactyly (extra digits on the ulnar/fibular side) is a classic skeletal finding. 4. **Other Core Features:** The pentad is completed by **Retinitis Pigmentosa** (leading to night blindness and visual loss) and **Mental Retardation** (intellectual disability). Renal anomalies are also frequently present. **Why other options are incorrect:** Options A, B, and C are individual components of the syndrome. Since all three are recognized cardinal features, selecting any single one would be incomplete. In NEET-PG, when multiple pathognomonic signs of a syndrome are listed, "All of the above" is the most appropriate choice. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Autosomal Recessive. * **Differentiation:** Historically, **Laurence-Moon Syndrome** (paraplegia, no polydactyly) and **Bardet-Biedl Syndrome** (polydactyly, obesity, renal issues) were distinct, but they are now often grouped together. * **Renal Failure:** This is the most common cause of morbidity and mortality in these patients. * **Mnemonic (PRBOH):** **P**olydactyly, **R**etinitis pigmentosa, **B**ehavioral/Mental issues, **O**besity, **H**ypogonadism.

Question 155: Which of the following is not a feature of congenital hypothyroidism?

A. Thyroid agenesis
B. Microcephaly (Correct Answer)
C. Wide open anterior fontanelle
D. Drooling

Explanation: **Explanation:** Congenital Hypothyroidism (CH) is one of the most common preventable causes of intellectual disability. The correct answer is **Microcephaly**, as it is not a feature of CH; instead, infants with CH often have a **normal or even slightly increased head circumference** due to myxedematous infiltration of the brain. **Analysis of Options:** * **Microcephaly (Correct Answer):** Microcephaly is typically associated with conditions like TORCH infections, chromosomal abnormalities, or fetal alcohol syndrome. In CH, brain growth is affected functionally (myelination and connectivity) rather than volumetrically in the neonatal period. * **Thyroid Agenesis:** This is the most common cause of permanent CH (Thyroid Dysgenesis). It accounts for approximately 80-85% of cases. * **Wide open anterior fontanelle:** Delayed skeletal maturation is a hallmark of CH. This manifests as large anterior and posterior fontanelles and the absence of the distal femoral epiphysis at birth. * **Drooling:** This occurs due to **macroglossia** (enlarged tongue), a classic sign caused by the accumulation of glycosaminoglycans in the tongue tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** Thyroid dysgenesis (Ectopy > Agenesis). * **Most common symptom:** Most infants are **asymptomatic at birth** due to the protective effect of maternal T4. * **Early signs:** Prolonged physiological jaundice, poor feeding, constipation, hoarse cry, and umbilical hernia. * **Screening:** Best done between **48–72 hours** of life to avoid the physiological TSH surge. * **Treatment:** Levothyroxine (10-15 mcg/kg/day) started immediately to prevent permanent neurocognitive impairment.

Question 156: Which of the following is NOT a symptom of neonatal hypothyroidism?

A. Open posterior fontanelle
B. Large tongue
C. Short stature
D. Hypertonia (Correct Answer)

Explanation: **Explanation:** Congenital hypothyroidism (CH) is one of the most common treatable causes of intellectual disability. The clinical presentation is often subtle at birth due to the protective effect of maternal thyroid hormones. **Why Hypertonia is the correct answer:** Hypothyroidism leads to a generalized slowing of metabolic processes and neuromuscular activity. Therefore, affected neonates typically present with **hypotonia** (floppiness) rather than hypertonia. Hypertonia is more characteristic of upper motor neuron lesions or certain metabolic disorders, but not hypothyroidism. **Analysis of Incorrect Options:** * **Open posterior fontanelle:** Delayed skeletal maturation is a hallmark of CH. A posterior fontanelle larger than 0.5 cm is a highly sensitive early clinical sign. * **Large tongue (Macroglossia):** This occurs due to the accumulation of glycosaminoglycans (myxedema) in the tissues. It can lead to feeding difficulties and respiratory obstruction. * **Short stature:** Thyroid hormone is essential for linear bone growth and epiphyseal maturation. Deficiency leads to growth retardation and limb-to-trunk disproportion. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** Dysgenesis (Aplasia, hypoplasia, or ectopic gland) is the most common cause of permanent CH. * **Early signs:** Prolonged physiological jaundice (due to delayed glucuronyl transferase activity), umbilical hernia, constipation, and a hoarse cry. * **Diagnosis:** Newborn screening (TSH/T4) is gold standard. Treatment must start within **2 weeks** of life to prevent permanent neurocognitive impairment. * **Radiological sign:** Absence of the distal femoral epiphysis on X-ray at birth (normally present at 36 weeks gestation) indicates intrauterine hypothyroidism.

Question 157: A 15-day-old neonate presents with seizures. Laboratory findings show serum calcium of 5 mg/dL, serum phosphate of 9 mg/dL, and intact PTH of 30 pg/mL (Normal intact PTH = 10-60 pg/mL). What is the most likely diagnosis?

A. Pseudohypoparathyroidism
B. Hypoparathyroidism (Correct Answer)
C. Vitamin D deficiency
D. Hypoxic Ischemic Encephalopathy

Explanation: ### Explanation The clinical presentation of seizures in a 15-day-old neonate with **hypocalcemia** (5 mg/dL) and **hyperphosphatemia** (9 mg/dL) points toward a defect in the Parathyroid Hormone (PTH) axis. **1. Why Hypoparathyroidism is correct:** In the presence of significant hypocalcemia, the physiological response of a healthy parathyroid gland is to secrete high levels of PTH (secondary hyperparathyroidism). In this case, the PTH is **30 pg/mL**, which is within the "normal" range. However, a normal PTH level in the setting of profound hypocalcemia is **inappropriate** and indicates a failure of the gland to respond, confirming **Hypoparathyroidism**. **2. Why the other options are incorrect:** * **Pseudohypoparathyroidism:** This is characterized by end-organ resistance to PTH. Laboratory findings would show hypocalcemia and hyperphosphatemia, but the **PTH level would be markedly elevated**. * **Vitamin D deficiency:** This typically presents with hypocalcemia and **hypophosphatemia** (due to secondary hyperparathyroidism causing phosphate wasting in the urine). PTH would be elevated. * **Hypoxic Ischemic Encephalopathy (HIE):** While HIE can cause neonatal seizures and metabolic disturbances, the specific biochemical pattern of inappropriately normal PTH with hyperphosphatemia specifically localizes the pathology to the parathyroid glands. **Clinical Pearls for NEET-PG:** * **PTH-Calcium Relationship:** Always interpret PTH in the context of serum calcium. A "normal" PTH during hypocalcemia is always pathological. * **DiGeorge Syndrome:** In a neonate with hypoparathyroidism, always look for associated features like congenital heart disease (CATCH-22) and immune deficiency. * **Early vs. Late Neonatal Tetany:** Early-onset (first 72 hours) is often due to prematurity or maternal diabetes; late-onset (after 72 hours) is often due to high phosphate intake (cow's milk) or primary hypoparathyroidism.

Question 158: Kleiner syndrome is diagnosed by?

A. Karyotyping (Correct Answer)
B. USG abdomen
C. Triple test
D. Echocardiography

Explanation: **Explanation:** **Kleiner syndrome** is an alternative name for **Klinefelter Syndrome (47, XXY)**. It is the most common sex chromosome aneuploidy in males, characterized by the presence of at least one extra X chromosome. **1. Why Karyotyping is the Correct Answer:** Since Klinefelter syndrome is a chromosomal disorder, **Karyotyping** is the gold standard and definitive diagnostic tool. It identifies the characteristic 47, XXY pattern (or variants like 48, XXXY). Karyotyping allows for the visualization of the extra X chromosome, which is responsible for the primary testicular failure and subsequent clinical features. **2. Why Other Options are Incorrect:** * **USG Abdomen:** While it might show small testes or be used to rule out other pathologies, it cannot provide a genetic diagnosis. * **Triple Test:** This is a maternal screening tool used during pregnancy to assess the risk of Trisomy 21, 18, and neural tube defects; it is not used to diagnose Klinefelter syndrome postnatally. * **Echocardiography:** Although patients with Klinefelter syndrome have a slightly higher risk of Mitral Valve Prolapse (MVP), it is not a diagnostic test for the syndrome itself. **Clinical Pearls for NEET-PG:** * **Clinical Features:** Tall stature, long limbs (eunuchoid habitus), small firm testes, gynecomastia, and infertility (azoospermia). * **Hormonal Profile:** **Increased LH and FSH** (due to loss of feedback inhibition) and **Decreased Testosterone**. * **Histology:** Hyalinization and fibrosis of seminiferous tubules with Leydig cell hyperplasia. * **Associated Risks:** Increased risk of Breast Cancer (20x), Germ cell tumors (Mediastinal), and Systemic Lupus Erythematosus (SLE). * **Barr Body:** Positive (unlike normal males who are Barr body negative).

Question 159: Hypercalcemia is seen in which of the following conditions?

A. Renal osteodystrophy
B. Vitamin D resistant rickets
C. Hypoparathyroidism
D. Williams syndrome (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Williams Syndrome** **Williams Syndrome** (also known as Williams-Beuren syndrome) is a multisystem genetic disorder caused by a microdeletion on chromosome **7q11.23** (involving the elastin gene). A classic metabolic feature of this syndrome, especially during infancy, is **idiopathic infantile hypercalcemia**. While the exact mechanism is not fully understood, it is thought to involve increased intestinal absorption of calcium and abnormal vitamin D metabolism. The hypercalcemia usually resolves by age 2–4 but can lead to nephrocalcinosis if severe. **Analysis of Incorrect Options:** * **A. Renal Osteodystrophy:** This typically presents with **hypocalcemia** (due to phosphate retention and decreased 1,25-dihydroxyvitamin D production) and secondary hyperparathyroidism. * **B. Vitamin D Resistant Rickets (Hypophosphatemic Rickets):** This is characterized by renal phosphate wasting. Calcium levels are typically **normal** or slightly low, but never high. * **C. Hypoparathyroidism:** A deficiency in Parathyroid Hormone (PTH) leads directly to **hypocalcemia** and hyperphosphatemia, as PTH is the primary hormone responsible for raising serum calcium. **High-Yield Clinical Pearls for NEET-PG:** * **Williams Syndrome Triad:** 1. **Elfin facies:** Full cheeks, wide mouth, prominent lips, and stellate iris pattern. 2. **Cardiovascular defects:** Most commonly **Supravalvular Aortic Stenosis (SVAS)** and peripheral pulmonary artery stenosis. 3. **Behavioral profile:** "Cocktail party personality" (extremely friendly/gregarious) with developmental delay. * **Mnemonic for Hypercalcemia:** "Stones (renal), Bones (pain), Groans (abdominal pain/constipation), and Psychic Moans (confusion)."

Question 160: A 5-year-old girl presents with hypertension and virilization. She also has hypokalemia. What is the diagnosis?

A. 21-hydroxylase deficiency
B. 3-beta-hydroxysteroid dehydrogenase deficiency
C. 11-beta-hydroxylase deficiency (Correct Answer)
D. Conn's disease

Explanation: ### Explanation The correct diagnosis is **11-beta-hydroxylase deficiency**, a subtype of Congenital Adrenal Hyperplasia (CAH). #### 1. Why 11-beta-hydroxylase deficiency is correct: In this condition, the enzyme deficiency leads to a block in the conversion of **11-deoxycorticosterone (DOC)** to corticosterone and **11-deoxycortisol** to cortisol. This results in: * **Virilization:** Low cortisol levels trigger an increase in ACTH, shunting precursors toward the androgen pathway. * **Hypertension & Hypokalemia:** The accumulation of **11-deoxycorticosterone (DOC)** is the key. DOC is a potent mineralocorticoid; its excess causes sodium retention (leading to hypertension) and potassium excretion (leading to hypokalemia). #### 2. Why the other options are incorrect: * **21-hydroxylase deficiency:** This is the most common CAH. While it causes virilization, it leads to **hypotension** and **hyperkalemia** (salt-wasting) due to a lack of mineralocorticoids. * **3-beta-hydroxysteroid dehydrogenase deficiency:** This rare form presents with salt-wasting (hypotension) and **incomplete virilization** in females or ambiguous genitalia in males. * **Conn's disease (Primary Hyperaldosteronism):** While it causes hypertension and hypokalemia, it does **not** cause virilization or androgen excess. #### 3. NEET-PG High-Yield Pearls: * **The "Rule of 11":** 11-beta-hydroxylase deficiency is the only common CAH that presents with **Hypertension** (11 has two 1s, like a high BP reading). * **Differentiating the "Hypertensive" CAHs:** * **11-beta-hydroxylase:** Hypertension + Virilization (Female). * **17-alpha-hydroxylase:** Hypertension + Sexual Infantilism/Delayed Puberty (Female). * **Most common cause of CAH:** 21-hydroxylase deficiency (90-95% of cases). * **Diagnostic Marker:** Elevated **11-deoxycortisol** and **11-deoxycorticosterone** in blood.

Practice by Chapter

Disorders of Growth

Practice Questions

Thyroid Disorders

Practice Questions

Disorders of Puberty

Practice Questions

Adrenal Disorders

Practice Questions

Diabetes Mellitus in Children

Practice Questions

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

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Endocrine Emergencies

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