Endocrinology — MCQs

A 15-day-old male neonate presented with failure to thrive, recurrent vomiting, and symptoms of shock. On examination, severe dehydration is noted. He has normal genitalia along with precocious development of pubic hair, phallic enlargement, and accelerated skeletal maturation. The child's blood pressure was normal. Lab findings revealed hyponatremia and hypokalemia, increased serum 17-hydroxyprogesterone, and increased urinary pregnanetriol. A biopsy from the adrenal gland was taken. Which of the following is the most likely enzyme deficiency in this patient?

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 61: Which of the following is NOT true about congenital hypothyroidism?

A. Females are more often affected (Correct Answer)
B. No signs at birth
C. Occurs due to antibodies against thyroid peroxisomes
D. Seen in 1:4000 live births

Explanation: **Explanation:** Congenital Hypothyroidism (CH) is the most common preventable cause of intellectual disability worldwide. **Analysis of the Options:** * **Option A (Correct Answer):** This statement is actually **TRUE**, not false. In cases of thyroid dysgenesis (the most common cause of CH), there is a significant female preponderance, with a female-to-male ratio of approximately **2:1**. Since the question asks for the statement that is "NOT true," and all other options are technically accurate descriptions of the disease, this question likely contains a technical error in its framing or key. However, in the context of NEET-PG, **Option C** is the most medically "false" statement regarding the primary etiology of CH. * **Option B:** Most infants have **no signs at birth** because of the transplacental transfer of maternal T4, which protects the fetal brain. Clinical features (prolonged jaundice, large fontanelle, umbilical hernia) usually appear after a few weeks. * **Option C:** This is **FALSE**. CH is most commonly caused by **Thyroid Dysgenesis** (85% - ectopy, aplasia, or hypoplasia) or **Dysmorgonogenesis** (15%). Antibodies against thyroid peroxidase (TPO) are associated with Hashimoto’s thyroiditis (acquired), not congenital hypothyroidism. * **Option D:** The worldwide incidence is approximately **1:3000 to 1:4000** live births. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** Thyroid Dysgenesis (specifically Ectopic thyroid). * **Most common cause of Goitrous CH:** Dyshormonogenesis (TPO defect). * **Screening:** Done at **48–72 hours** of life to avoid the physiological TSH surge. * **Treatment:** Levothyroxine (10–15 μg/kg/day) should be started immediately to prevent permanent neurodevelopmental delay. * **Radiology:** Absence of the **distal femoral epiphysis** at birth is a sign of intrauterine hypothyroidism.

Question 62: A 2-week-old infant presents with feeding difficulties, somnolence, failure to thrive, and constipation. Blood studies reveal low T4 and high TSH. If appropriate therapy is not promptly instituted, which of the following complications would most likely occur?

A. Bronchiectasis
B. Gigantism
C. Hepatic cirrhosis
D. Mental retardation (Correct Answer)

Explanation: ### **Explanation** The clinical presentation of feeding difficulties, somnolence (lethargy), constipation, and failure to thrive in a 2-week-old, combined with laboratory findings of **low T4 and high TSH**, is diagnostic of **Congenital Hypothyroidism (CH)**. #### **Why Mental Retardation is Correct** Thyroid hormones (T3/T4) are critical for early brain development, specifically for **neurogenesis, axonal myelination, and dendritic branching**. During the first few months of life, the brain is highly dependent on thyroid hormone for structural maturation. If untreated, the lack of T4 leads to irreversible neurological damage, making Congenital Hypothyroidism the **most common preventable cause of mental retardation** worldwide. #### **Why Other Options are Incorrect** * **A. Bronchiectasis:** This is a chronic lung condition (permanent dilation of bronchi) often associated with Cystic Fibrosis or recurrent infections, not thyroid deficiency. * **B. Gigantism:** This results from an excess of Growth Hormone (GH) before epiphyseal closure. Hypothyroidism actually causes **growth failure and short stature**. * **C. Hepatic Cirrhosis:** While CH can cause prolonged physiological jaundice (unconjugated hyperbilirubinemia) due to delayed glucuronyl transferase activity, it does not lead to cirrhosis. --- ### **High-Yield Clinical Pearls for NEET-PG** * **Most Common Cause:** Thyroid dysgenesis (Ectopy is the most common specific type; Agenesis is the most severe). * **Earliest Sign:** Prolonged physiological jaundice. * **Classic Signs:** Large fontanelles (especially posterior), umbilical hernia, macroglossia, and a "hoarse cry." * **Screening:** Ideally done between **48–72 hours** of life. Screening earlier may yield a false positive due to the physiological neonatal TSH surge. * **Radiology:** Absence of the **distal femoral epiphysis** on X-ray at birth suggests in-utero hypothyroidism. * **Treatment:** Immediate replacement with **Levothyroxine** (10–15 μg/kg/day). The goal is to normalize T4 within 2 weeks to prevent neurocognitive deficits.

Question 63: A cherry red spot is seen in which of the following conditions?

A. Tay-Sachs disease (Correct Answer)
B. Batten-Mayou disease
C. von Gierke's disease
D. Mucopolysaccharidosis

Explanation: **Explanation:** The **cherry red spot** is a classic ophthalmological finding caused by the accumulation of lipids or complex carbohydrates in the retinal ganglion cells. This accumulation makes the surrounding retina appear pale or opaque, while the central fovea (which lacks ganglion cells) allows the underlying vascular choroid to show through, appearing as a bright red spot. **1. Why Tay-Sachs Disease is Correct:** Tay-Sachs is a lysosomal storage disorder caused by a deficiency of the enzyme **Hexosaminidase A**, leading to the accumulation of **GM2 gangliosides**. This accumulation is particularly heavy in the retinal ganglion cells, making it the most classic association for a cherry red spot in pediatric exams. **2. Analysis of Incorrect Options:** * **Batten-Mayou disease:** Also known as Juvenile Neuronal Ceroid Lipofuscinosis. While it involves retinal degeneration and "bull’s eye maculopathy," it typically presents with optic atrophy and pigmentary changes rather than a classic cherry red spot. * **von Gierke's disease:** This is Type I Glycogen Storage Disease. It primarily affects the liver and kidneys (hypoglycemia, hepatomegaly). It does not involve the deposition of substances in the retina. * **Mucopolysaccharidosis (MPS):** Most MPS types (like Hurler syndrome) are characterized by **corneal clouding**, which actually obscures the view of the retina, making a cherry red spot an unlikely finding. **Clinical Pearls for NEET-PG:** * **Mnemonic for Cherry Red Spot:** "Check My Apple, Sandhoff's Next" (**C**herry red spot: **C**entral retinal artery occlusion, **M**etachromatic leukodystrophy, **A**mautic idiocy/Tay-Sachs, **S**andhoff disease, **N**iemann-Pick disease). * **Differentiating Tay-Sachs vs. Niemann-Pick:** Both have a cherry red spot, but **Niemann-Pick** presents with **hepatosplenomegaly**, whereas Tay-Sachs does not. * **Gaucher Disease:** Generally does *not* feature a cherry red spot (except for the very rare Type 3).

Question 64: Late onset of puberty in the male is defined as:

A. Puberty onset after 16 years (Correct Answer)
B. Puberty onset after 17 years
C. Puberty onset after 18 years
D. Puberty onset after 21 years

Explanation: **Explanation:** The definition of delayed puberty (Late onset of puberty) is based on the statistical upper limit of normal for the onset of secondary sexual characteristics. In males, puberty is considered delayed if there is **no evidence of testicular enlargement (volume < 4 ml or length < 2.5 cm) by the age of 14 years.** However, in the context of clinical milestones and specific academic definitions often tested in exams like NEET-PG, the **complete absence of any signs of puberty by age 16** is the definitive threshold for "Late onset." **Analysis of Options:** * **Option A (Correct):** By age 16, 99% of healthy males have entered puberty. Failure to do so indicates a pathological delay or a significant constitutional delay requiring investigation. * **Options B, C, and D:** These ages (17, 18, and 21) are well beyond the standard physiological window. While a patient might present at these ages, the clinical diagnosis of "delayed puberty" would have been established much earlier (at age 14 or 16). **High-Yield Clinical Pearls for NEET-PG:** * **First sign of puberty in males:** Testicular enlargement (due to growth of seminiferous tubules under FSH influence). * **Most common cause:** Constitutional Delay of Growth and Puberty (CDGP) – often associated with a positive family history and delayed bone age. * **Prader-Willi Syndrome:** A common syndromic cause of hypogonadotropic hypogonadism. * **Kallmann Syndrome:** Delayed puberty associated with anosmia (failure of GnRH neuron migration). * **Precocious Puberty (Male):** Onset of secondary sexual characters before **9 years** of age.

Question 65: Which of the following effects is NOT seen in primary hyperaldosteronism?

A. Hypertension
B. Metabolic alkalosis
C. Hyperkalemia (Correct Answer)
D. Expansion of extracellular and plasma volume

Explanation: **Explanation:** Primary hyperaldosteronism (Conn’s Syndrome) is characterized by the autonomous overproduction of aldosterone from the adrenal cortex. To understand the clinical manifestations, one must recall the action of aldosterone on the **principal cells** and **alpha-intercalated cells** of the renal collecting duct. **Why Hyperkalemia is the Correct Answer:** Aldosterone increases the activity of ENaC (epithelial sodium channels) and the Na+/K+ ATPase pump. This leads to increased sodium reabsorption in exchange for **potassium secretion** into the tubular lumen. Consequently, primary hyperaldosteronism causes **hypokalemia**, not hyperkalemia. Therefore, Option C is the "except" or incorrect effect. **Analysis of Incorrect Options:** * **Hypertension (Option A):** Increased sodium reabsorption leads to water retention, increasing peripheral resistance and cardiac output, resulting in hypertension. * **Metabolic Alkalosis (Option B):** Aldosterone stimulates the H+-ATPase pump in alpha-intercalated cells, leading to increased secretion of hydrogen ions into the urine. The loss of H+ ions results in systemic metabolic alkalosis. * **Expansion of ECF and Plasma Volume (Option C):** Sodium and water retention lead to volume expansion. However, clinical edema is rarely seen due to the **"Aldosterone Escape"** phenomenon (where increased ANP levels cause pressure natriuresis). **High-Yield Clinical Pearls for NEET-PG:** * **Screening Test:** Plasma Aldosterone Concentration (PAC) to Plasma Renin Activity (PRA) ratio. A ratio **>20-30** is suggestive. * **Confirmatory Test:** Saline infusion test or Oral salt loading test (failure to suppress aldosterone). * **Aldosterone Escape:** Explains why patients with primary hyperaldosteronism have hypertension and hypernatremia but **no edema**. * **Muscle Weakness:** A common presenting symptom due to profound hypokalemia.

Question 66: Growth hormone (GH) deficiency is diagnosed by which of the following findings?

A. Bone age less than chronological age (Correct Answer)
B. Bone age more than chronological age
C. Bone age equal to chronological age
D. Ratio of upper to lower segment of body is increased

Explanation: In Growth Hormone (GH) deficiency, the primary clinical hallmark is **short stature with delayed skeletal maturation**. ### **Explanation of the Correct Answer** **Option A (Bone age < Chronological age):** Growth hormone is essential for the linear growth of long bones and the maturation of epiphyses. In GH deficiency, there is a significant delay in the appearance and fusion of ossification centers. Consequently, the **Bone Age (BA)**—determined by an X-ray of the left hand and wrist—is significantly lagging behind the **Chronological Age (CA)**. This delay is usually more than 2 standard deviations below the mean. ### **Analysis of Incorrect Options** * **Option B:** Bone age greater than chronological age (Advanced Bone Age) is seen in conditions with excess sex steroids, such as **Precocious Puberty** or **Congenital Adrenal Hyperplasia (CAH)**. * **Option C:** Bone age equal to chronological age is characteristic of **Genetic (Familial) Short Stature**, where the child is short but maturing at a normal rate. * **Option D:** An increased upper-to-lower segment ratio (disproportionate short stature) is typical of **Hypothyroidism** or skeletal dysplasias like **Achondroplasia**. In GH deficiency, the body proportions remain normal (proportionate short stature). ### **High-Yield Clinical Pearls for NEET-PG** * **Gold Standard Diagnosis:** GH deficiency is diagnosed using **GH Stimulation Tests** (using Insulin, Arginine, or Clonidine). A peak GH level **<10 ng/mL** is diagnostic. * **Screening Test:** Measurement of **IGF-1** and **IGFBP-3** levels (more stable than pulsatile GH). * **Clinical Features:** "Cherubic" appearance (doll-like face), truncal obesity, high-pitched voice, and micropenis (if associated with gonadotropin deficiency). * **Constitutional Delay of Growth and Puberty (CDGP):** Also shows BA < CA, but unlike GH deficiency, these children eventually achieve their target height.

Question 67: A 15-year-old boy with cystic fibrosis presents with a 3-6 kg weight loss over the past month, unaccompanied by changes in his pulmonary and gastrointestinal symptoms. Which of the following is most suspected?

A. Bronchogenic carcinoma
B. Eating disorder
C. Biliary cirrhosis
D. Diabetes mellitus (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Diabetes Mellitus** The most likely diagnosis is **Cystic Fibrosis-Related Diabetes (CFRD)**. In Cystic Fibrosis (CF), thick secretions lead to progressive scarring and destruction of the pancreatic islet cells, causing a deficiency in insulin secretion. * **Why it fits:** Weight loss in a CF patient who is otherwise stable (no increase in cough, sputum, or malabsorption) is a classic red flag for CFRD. As insulin is an anabolic hormone, its deficiency leads to catabolism and weight loss despite adequate caloric intake. CFRD is the most common extra-pulmonary complication of CF, affecting nearly 20% of adolescents and 40-50% of adults. **Analysis of Incorrect Options:** * **A. Bronchogenic Carcinoma:** While CF increases the risk of certain malignancies, lung cancer is rare in a 15-year-old. Furthermore, weight loss from malignancy would typically be accompanied by worsening pulmonary symptoms. * **B. Eating Disorder:** While possible in any adolescent, the physiological link between CF and pancreatic endocrine failure makes CFRD a much more high-yield and likely clinical suspicion. * **C. Biliary Cirrhosis:** While CF-associated liver disease occurs, it usually presents with hepatosplenomegaly, jaundice, or portal hypertension rather than isolated rapid weight loss without GI distress. **NEET-PG High-Yield Pearls:** * **Screening:** Annual screening for CFRD using the **Oral Glucose Tolerance Test (OGTT)** should begin at **age 10** for all CF patients. * **Pathophysiology:** It is a unique entity—not Type 1 (not autoimmune) and not Type 2 (primarily insulin deficiency, not resistance). * **Treatment:** **Insulin** is the only recommended treatment. Oral hypoglycemic agents are generally not effective. * **Clinical Clue:** Unexplained decline in pulmonary function or weight loss in a CF patient is the most common presentation of CFRD.

Question 68: Pseudohypoparathyroidism is characterized by which of the following laboratory findings?

A. Normal serum calcium and decreased serum parathyroid hormone
B. Decreased serum calcium and decreased serum parathyroid hormone
C. Decreased serum calcium and increased serum parathyroid hormone (Correct Answer)
D. Normal serum calcium and increased serum parathyroid hormone

Explanation: ### Explanation **Pseudohypoparathyroidism (PHP)** is a group of disorders characterized by **end-organ resistance** to Parathyroid Hormone (PTH). The primary defect lies in the GNAS1 gene, which affects the G-protein signaling pathway required for PTH to act on its receptors in the kidneys and bones. **1. Why Option C is Correct:** Because the kidneys and bones are "deaf" to PTH, the body cannot effectively reabsorb calcium or excrete phosphate. This leads to **hypocalcemia** and hyperphosphatemia. In response to low calcium levels, the parathyroid glands function normally and increase production of PTH via a feedback loop. Therefore, the hallmark laboratory finding is **decreased serum calcium and increased serum PTH.** **2. Why Incorrect Options are Wrong:** * **Option A & B:** Decreased PTH is characteristic of **Hypoparathyroidism** (e.g., post-surgical or DiGeorge syndrome), not "Pseudo" hypoparathyroidism. In PHP, the gland itself is healthy and hyperactive. * **Option D:** Normal calcium with high PTH is seen in **Secondary Hyperparathyroidism** (early stages) or **Pseudopseudohypoparathyroidism (PPHP)**, where the phenotypic features are present without the biochemical abnormalities. **3. High-Yield Clinical Pearls for NEET-PG:** * **Albright Hereditary Osteodystrophy (AHO):** This is the classic phenotype of PHP Type 1a, featuring short stature, round face, obesity, and **short 4th/5th metacarpals** (Archibald’s sign). * **Ellsworth-Howard Test:** Historically used to differentiate PHP from hypoparathyroidism; in PHP, there is a failure of urinary cAMP to rise following an infusion of exogenous PTH. * **Basal Ganglia Calcification:** Chronic hypocalcemia in these patients can lead to intracranial calcifications and seizures.

Question 69: Rickets in the neonatal period and early infancy present as all EXCEPT:

A. Craniotabes
B. Widened fontanel
C. Rachitic Rosary
D. Bow legs (Correct Answer)

Explanation: The clinical presentation of rickets is highly dependent on the **age of the child** and the **mechanical stresses** acting on the skeleton at that time. ### **Explanation of the Correct Answer** **D. Bow legs (Genu Varum):** This is the correct answer because it is **not** seen in neonates or early infants. Bowing of the legs is a weight-bearing deformity. It occurs only after the child begins to stand or walk (typically after 1 year of age), as the softened, unmineralized osteoid in the lower limbs bends under the effect of gravity and body weight. ### **Explanation of Incorrect Options** * **A. Craniotabes:** This is the **earliest sign of rickets**, often seen in infants under 6 months. It refers to the softening of the skull bones (especially the occiput and parietal bones), which feel like a "ping-pong ball" when pressed. * **B. Widened fontanel:** Rickets causes a delay in the closure of the anterior fontanel and widening of the sutures due to impaired mineralization of the skull bones. * **C. Rachitic Rosary:** This is a classic early sign caused by the expansion of the osteochondral junctions of the ribs. It is palpable (and sometimes visible) as bead-like prominences on the chest wall. ### **NEET-PG High-Yield Pearls** * **Earliest Sign:** Craniotabes (though it can be physiological in newborns, its persistence suggests rickets). * **Earliest Radiological Sign:** Cupping and splaying of the distal ends of long bones (best seen at the **distal ulna**). * **Sequence of Deformities:** * *Infancy:* Craniotabes, Rachitic Rosary, Harrison’s Sulcus. * *Toddler (Weight-bearing):* Genu Varum (Bow legs). * *Older Children:* Genu Valgum (Knock knees). * **Biochemical Hallmark:** Elevated **Alkaline Phosphatase (ALP)** is the most sensitive marker for active rickets.

Question 70: A 15-day-old male neonate presented with failure to thrive, recurrent vomiting, and symptoms of shock. On examination, severe dehydration is noted. He has normal genitalia along with precocious development of pubic hair, phallic enlargement, and accelerated skeletal maturation. The child's blood pressure was normal. Lab findings revealed hyponatremia and hypokalemia, increased serum 17-hydroxyprogesterone, and increased urinary pregnanetriol. A biopsy from the adrenal gland was taken. Which of the following is the most likely enzyme deficiency in this patient?

A. 21-hydroxylase deficiency (Correct Answer)
B. 11-hydroxylase deficiency
C. 3-beta-hydroxysteroid dehydrogenase deficiency
D. 17-hydroxylase deficiency

Explanation: ### **Explanation** The clinical presentation describes a classic case of **Congenital Adrenal Hyperplasia (CAH)**, specifically the **Salt-Wasting form of 21-Hydroxylase deficiency**. **1. Why 21-Hydroxylase Deficiency is Correct:** * **Pathophysiology:** A deficiency in 21-hydroxylase prevents the conversion of Progesterone to Deoxycorticosterone (Mineralocorticoid pathway) and 17-OHP to 11-deoxycortisol (Glucocorticoid pathway). * **Salt-Wasting:** Low aldosterone leads to **hyponatremia, hyperkalemia**, dehydration, and shock. (Note: The question mentions hypokalemia, which is likely a typographical error in the stem; CAH typically presents with **hyperkalemia**). * **Virilization:** Excess precursors are shunted toward androgen synthesis. In males, this causes phallic enlargement and precocious pubic hair (isosexual precocity). * **Biomarkers:** Elevated **17-hydroxyprogesterone (17-OHP)** and urinary **pregnanetriol** are pathognomonic. **2. Why Other Options are Incorrect:** * **11-beta-hydroxylase deficiency:** While it causes virilization, it leads to **hypertension** (due to accumulation of 11-deoxycorticosterone, a weak mineralocorticoid) and **hypokalemia**. * **3-beta-hydroxysteroid dehydrogenase deficiency:** This occurs earlier in the pathway. It results in salt-wasting but causes **undervirilization** (ambiguous genitalia) in males because testosterone cannot be synthesized. * **17-alpha-hydroxylase deficiency:** This leads to increased mineralocorticoids (**hypertension/hypokalemia**) but **decreased sex hormones**, resulting in delayed puberty and female phenotypes in males. **3. NEET-PG High-Yield Pearls:** * **Most Common Cause:** 21-hydroxylase deficiency accounts for >90% of CAH cases. * **Genetics:** Autosomal Recessive; associated with the **CYP21A2** gene. * **Diagnosis:** Elevated 17-OHP is the gold standard for screening. * **Management:** Acute crisis requires aggressive fluid resuscitation (Normal Saline) and IV Hydrocortisone. Long-term treatment involves glucocorticoid and mineralocorticoid (Fludrocortisone) replacement.

Practice by Chapter

Disorders of Growth

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Thyroid Disorders

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Disorders of Puberty

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Adrenal Disorders

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Diabetes Mellitus in Children

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Disorders of Calcium and Phosphate Metabolism

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Disorders of Sexual Development

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Hypoglycemia

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Obesity and Metabolic Syndrome

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Pituitary Disorders

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Multiple Endocrine Neoplasia Syndromes

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Endocrine Emergencies

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