Endocrinology Practice Questions

Q: A 3-week-old female infant presents with ambiguous genitalia and hyperpigmentation of the skin. Laboratory findings include hyponatremia and hyperkalemia. What is the most likely diagnosis?

21 hydroxylase deficiency. ***21 hydroxylase deficiency*** - This is the most common form of Congenital Adrenal Hyperplasia (CAH) where a lack of cortisol leads to high **ACTH**, resulting in adrenal hyperplasia and skin **hyperpigmentation**. - Reduced mineralocorticoids cause **hyponatremia** and **hyperkalemia**, while shunted precursors increase androgens, causing **ambiguous genitalia** in females. *17 alpha hydroxylase deficiency* - This condition leads to a decrease in androgens and cortisol, resulting in **normal female external genitalia** but phenotypic males appearing female. - It causes an excess of mineralocorticoids, leading to **hypertension** and hypokalemia, which contradicts the laboratory findings provided. *17, 20 lyase deficiency* - This enzyme deficiency selectively impairs the production of **sex hormones** (androgens and estrogens) without affecting cortisol or aldosterone. - It does not present with **salt-wasting** (hyponatremia/hyperkalemia) or skin hyperpigmentation, as the mineralocorticoid and glucocorticoid pathways remain intact. *11 beta hydroxylase deficiency* - While this deficiency causes androgen excess and **virilization** of females, it leads to the accumulation of 11-deoxycorticosterone, a potent mineralocorticoid. - The resulting clinical picture includes **hypertension** and hypokalemia rather than the hyponatremic/hyperkalemic salt-wasting state seen in this infant.

Q: Cretinism is characterized by which of the following physical features?

Disproportionate dwarfism. **Explanation:** **Cretinism** (Congenital Hypothyroidism) results from a deficiency of thyroid hormones during fetal or neonatal life. Thyroid hormone is essential for skeletal maturation and linear growth. In its absence, there is a significant delay in bone age and the maturation of the epiphyseal centers. **Why Option A is Correct:** The hallmark of cretinism is **disproportionate dwarfism**. Thyroid hormone is critical for the growth of long bones. When deficient, the limbs remain short while the trunk continues to grow relatively more, leading to a **low upper segment to lower segment (US:LS) ratio** for the child's age (retaining the infantile proportions where the upper segment is longer). This is distinct from growth hormone deficiency, which typically causes proportionate dwarfism. **Why Other Options are Incorrect:** * **Options B & C:** These descriptions are inaccurate. While the trunk may appear "long" relative to the limbs, the standard clinical terminology is "disproportionate." Short-trunk dwarfism is more characteristic of skeletal dysplasias like Morquio syndrome. * **Option D:** Hypothyroidism leads to growth retardation, not long stature. **Clinical Pearls for NEET-PG:** * **Most common cause:** Thyroid dysgenesis (Ectopic thyroid is the most common specific etiology). * **Early signs:** Prolonged physiological jaundice, poor feeding, constipation, and a large posterior fontanelle (>0.5 cm). * **Classic triad:** Coarse facies, macroglossia (large tongue), and umbilical hernia. * **Radiology:** Absence of the distal femoral epiphysis at birth is a strong indicator of in utero hypothyroidism. * **Treatment:** Levothyroxine (T4) must be started within the first 2 weeks of life to prevent permanent intellectual disability.

Q: A mother reports that her 2-week-old infant sleeps most of the day and needs to be awakened every 4 hours for feeding, taking only one ounce of formula at a time. She is also concerned about the infant's persistently hard, pellet-like stools. Examination reveals an infant with normal weight and length, but with an enlarged head, a heart rate of 75 beats per minute, a temperature of 35°C (95°F), persistent jaundice, large anterior and posterior fontanelles, a distended abdomen, and an umbilical hernia. This clinical presentation is likely a result of which of the following?

Congenital hypothyroidism. ### Explanation **Correct Answer: A. Congenital Hypothyroidism** This infant presents with the classic "quiet baby" syndrome of **Congenital Hypothyroidism (CH)**. Thyroid hormones are essential for metabolic processes and neurological development. A deficiency leads to a generalized slowing of body functions, manifesting as: * **Metabolic slowing:** Hypothermia (35°C), bradycardia (75 bpm), and lethargy (sleeping most of the day). * **Gastrointestinal:** Decreased motility leads to constipation (hard, pellet-like stools), poor feeding, and abdominal distension. * **Structural signs:** Large anterior and posterior fontanelles (delayed bone age), umbilical hernia, and macroglossia (often causing feeding issues). * **Jaundice:** Prolonged unconjugated hyperbilirubinemia due to delayed glucuronyl transferase activity. **Why other options are incorrect:** * **B. Hirschsprung Disease:** While it causes constipation, abdominal distension, and potentially an umbilical hernia, it does **not** explain the bradycardia, hypothermia, large fontanelles, or prolonged jaundice. * **C. Sepsis:** Can cause lethargy, poor feeding, and temperature instability, but it is an acute presentation. It would not explain the large fontanelles or umbilical hernia. * **D. Infantile Botulism:** Presents with "floppy baby" syndrome (hypotonia) and constipation, but typically occurs in slightly older infants (after honey ingestion) and does not feature the structural/metabolic signs of CH. **NEET-PG High-Yield Pearls:** * **Most common cause:** Dysgenesis (Agenesis/Ectopy) of the thyroid gland. * **Most sensitive screening test:** Serum TSH (usually performed via heel prick on day 3–5). * **Clinical Clue:** A posterior fontanelle >0.5 cm in a term neonate is highly suggestive of CH. * **Treatment:** Levothyroxine (10–15 μg/kg/day). Early treatment (within 2 weeks) is critical to prevent permanent intellectual disability (Cretinism).

Question 1

A 3-week-old female infant presents with ambiguous genitalia and hyperpigmentation of the skin. Laboratory findings include hyponatremia and hyperkalemia. What is the most likely diagnosis?

Accepted Answer

21 hydroxylase deficiency

Answer

17 alpha hydroxylase deficiency

Answer

17, 20 lyase deficiency

Answer

11 beta hydroxylase deficiency

Question 2

Cretinism is characterized by which of the following physical features?

Accepted Answer

Disproportionate dwarfism

Answer

Short stature with a long trunk

Answer

Short stature with a short trunk

Answer

Long stature with a long trunk

Question 3

What is the least common cause of ambiguous genitalia in a female genotype?

Accepted Answer

Fetal steroid sulphatase deficiency

Answer

21 hydroxylase deficiency

Answer

11 hydroxylase deficiency

Answer

WT1 gene

Question 4

A mother reports that her 2-week-old infant sleeps most of the day and needs to be awakened every 4 hours for feeding, taking only one ounce of formula at a time. She is also concerned about the infant's persistently hard, pellet-like stools. Examination reveals an infant with normal weight and length, but with an enlarged head, a heart rate of 75 beats per minute, a temperature of 35°C (95°F), persistent jaundice, large anterior and posterior fontanelles, a distended abdomen, and an umbilical hernia. This clinical presentation is likely a result of which of the following?

Accepted Answer

Congenital hypothyroidism

Answer

Congenital megacolon (Hirschsprung disease)

Answer

Sepsis

Answer

Infantile botulism

Question 5

A previously healthy 6-week-old female infant is found unresponsive in her crib. She is well-developed and well-nourished with normal blood pressure and appearance of the genitalia but has increased pigmentation of her skin. Her blood glucose level is 30 mg/dl. What is the most likely diagnosis?

Accepted Answer

Familial glucocorticoid deficiency

Answer

Congenital adrenal hyperplasia due to 21-alpha hydroxylase deficiency

Answer

Cushing syndrome

Answer

Insulinoma

Endocrinology — MCQs

Endocrinology — MCQs

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