Endocrinology

Endocrinology Indian Medical PG 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?

• A. 21 hydroxylase deficiency (Correct Answer)
• B. 17 alpha hydroxylase deficiency
• C. 17, 20 lyase deficiency
• D. 11 beta hydroxylase deficiency

Endocrinology Explanation: **Explanation:** The clinical presentation of ambiguous genitalia in a female infant, skin hyperpigmentation, and electrolyte imbalances (hyponatremia and hyperkalemia) is classic for **Congenital Adrenal Hyperplasia (CAH)**, specifically **21-hydroxylase deficiency**. **1. Why 21-hydroxylase deficiency is correct:** This is the most common cause of CAH (>90%). A deficiency in this enzyme blocks the conversion of progesterone to deoxycorticosterone (mineralocorticoid pathway) and 17-OH progesterone to 11-deoxycortisol (glucocorticoid pathway). * **Mineralocorticoid deficiency:** Leads to "salt-wasting" (hyponatremia, hyperkalemia, and hypotension). * **Glucocorticoid deficiency:** Triggers a feedback increase in ACTH, causing **hyperpigmentation** (due to shared precursor with MSH) and adrenal hyperplasia. * **Androgen excess:** Shunting of precursors toward the androgen pathway causes virilization/ambiguous genitalia in females. **2. Why other options are incorrect:** * **11-beta hydroxylase deficiency:** While it causes virilization and hyperpigmentation, it leads to **hypertension** and hypokalemia because 11-deoxycortisol (which builds up) has mineralocorticoid activity. * **17-alpha hydroxylase deficiency:** This results in decreased sex hormones. Females would have normal external genitalia at birth but fail puberty; males would present with ambiguous genitalia/pseudohermaphroditism. It also causes hypertension. * **17, 20 lyase deficiency:** This affects only sex hormone synthesis. It does not cause salt-wasting or hyperpigmentation as cortisol and aldosterone pathways remain intact. **High-Yield Pearls for NEET-PG:** * **Most common enzyme deficiency:** 21-hydroxylase. * **Diagnostic marker:** Elevated **17-hydroxyprogesterone (17-OHP)**. * **Karyotype:** Usually 46, XX in virilized females. * **Treatment:** Glucocorticoid (Hydrocortisone) and Mineralocorticoid (Fludrocortisone) replacement.

Endocrinology Indian Medical PG Question 2: Deep white matter lesion with bilateral deep bright thalamic appearance is suggestive of which condition?

• A. Alexander disease
• B. Canavan's disease
• C. Krabbe's disease (Correct Answer)
• D. Metachromatic leukodystrophy

Endocrinology Explanation: ### Explanation **Krabbe’s Disease (Globoid Cell Leukodystrophy)** The correct answer is **Krabbe’s Disease**. This is an autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme **Galactocerebrosidase (GALC)**, leading to the accumulation of psychosine, which is toxic to oligodendrocytes. The characteristic neuroimaging finding in the early infantile stage is **hyperdensity (on CT)** or **T2-weighted hypointensity/T1-weighted hyperintensity (on MRI)** in the **thalami**, caudate nuclei, and posterior limb of the internal capsule. This "bright thalamus" appearance, combined with symmetric demyelination of the deep white matter and cerebellar involvement, is a classic diagnostic clue for Krabbe’s. **Analysis of Incorrect Options:** * **Alexander Disease:** Characterized by **frontal lobe predominance** of white matter lesions and "Rosenthal fibers" on pathology. It often presents with macrocephaly. * **Canavan’s Disease:** Notable for **diffuse** white matter involvement including the **subcortical U-fibers** (which are spared in Krabbe’s and MLD) and elevated N-acetylaspartate (NAA) on MR spectroscopy. It also presents with macrocephaly. * **Metachromatic Leukodystrophy (MLD):** Shows a characteristic **"tigroid" or "leopard skin" pattern** of demyelination due to the sparing of perivascular white matter. It typically spares the thalami in early stages. **High-Yield Clinical Pearls for NEET-PG:** * **Krabbe’s:** Look for "Globoid cells" (multinucleated macrophages) on brain biopsy and optic atrophy. * **Macrocephaly + Leukodystrophy:** Think Alexander disease or Canavan’s disease. * **Microcephaly + Leukodystrophy:** Think Krabbe’s disease. * **Tigroid Pattern:** Pathognomonic for MLD (Arylsulfatase A deficiency).

Endocrinology Indian Medical PG Question 3: Cretinism is characterized by which of the following physical features?

• A. Disproportionate dwarfism (Correct Answer)
• B. Short stature with a long trunk
• C. Short stature with a short trunk
• D. Long stature with a long trunk

Endocrinology Explanation: **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.

Endocrinology Indian Medical PG Question 4: Which of the following is a manifestation of 22q11 deletion syndrome?

• A. Hypercalcemia
• B. Conotruncal abnormalities (Correct Answer)
• C. Thymic hyperplasia
• D. Dysmorphogenesis of the 1st and 2nd pharyngeal pouches

Endocrinology Explanation: **Explanation:** **22q11.2 Deletion Syndrome** (which encompasses DiGeorge Syndrome and Velocardiofacial Syndrome) results from a microdeletion leading to the defective development of the **3rd and 4th pharyngeal pouches**. 1. **Why Option B is Correct:** **Conotruncal cardiac abnormalities** are a hallmark of this syndrome, occurring in approximately 75% of patients. These include **Tetralogy of Fallot (most common)**, Interrupted Aortic Arch (Type B), Truncus Arteriosus, and Ventricular Septal Defects. These defects arise due to the failure of neural crest cell migration into the developing outflow tract. 2. **Why the Other Options are Incorrect:** * **A. Hypercalcemia:** Patients actually present with **Hypocalcemia**. This is due to parathyroid hypoplasia (derived from the 3rd/4th pouches), leading to low PTH levels and subsequent tetany or seizures, especially in the neonatal period. * **C. Thymic hyperplasia:** The syndrome is characterized by **Thymic hypoplasia or aplasia**, leading to T-cell deficiency and increased susceptibility to viral and fungal infections. * **D. Dysmorphogenesis of 1st/2nd pouches:** The defect specifically involves the **3rd and 4th pharyngeal pouches**. The 1st and 2nd pouches contribute to the middle ear, tonsils, and tongue, which are not the primary sites of pathology in 22q11 deletion. **High-Yield Clinical Pearls for NEET-PG:** * **CATCH-22 Mnemonic:** **C**ardiac defects, **A**bnormal facies (low-set ears, cleft palate), **T**hymic hypoplasia, **C**left palate, **H**ypocalcemia, **22**q11 deletion. * **Diagnosis:** Gold standard is **FISH** (Fluorescence In Situ Hybridization) or chromosomal microarray. * **Chest X-ray:** Look for the **absence of a thymic shadow** in a neonate.

Endocrinology Indian Medical PG Question 5: What is the least common cause of ambiguous genitalia in a female genotype?

• A. 21 hydroxylase deficiency
• B. 11 hydroxylase deficiency
• C. Fetal steroid sulphatase deficiency (Correct Answer)
• D. WT1 gene

Endocrinology Explanation: **Explanation:** Ambiguous genitalia in a female genotype (46,XX) is most commonly caused by **Female Pseudohermaphroditism**, where an excess of androgens leads to virilization of a genetically female fetus. **Why Option C is correct:** **Fetal Steroid Sulphatase Deficiency** (also known as Placental Sulphatase Deficiency) is associated with **X-linked Ichthyosis**. In this condition, the placenta cannot convert DHEAS into estriol. This leads to extremely low maternal serum estriol levels and failure of labor induction. Crucially, it **does not** cause virilization or ambiguous genitalia in the female fetus. In fact, it is a condition primarily affecting male fetuses (X-linked), making it the "least common" (or non-existent) cause among the choices provided. **Analysis of Incorrect Options:** * **A. 21-Hydroxylase Deficiency:** This is the **most common** cause of ambiguous genitalia in 46,XX (responsible for ~90% of Congenital Adrenal Hyperplasia cases). It causes a "salt-wasting" or "simple virilizing" crisis due to shunting of precursors to androgens. * **B. 11-Beta-Hydroxylase Deficiency:** The second most common cause of CAH. It causes virilization in females and is uniquely associated with **hypertension** due to the accumulation of 11-deoxycorticosterone (DOC). * **D. WT1 Gene Mutations:** Mutations in the Wilms Tumor 1 gene (e.g., Denys-Drash or Frasier Syndrome) typically cause 46,XY gonadal dysgenesis, but they are recognized causes of complex disorders of sexual development (DSD) and can present with ambiguous genitalia. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of 46,XX DSD:** Congenital Adrenal Hyperplasia (21-OH deficiency). * **Maternal cause of female virilization:** Luteoma of pregnancy or intake of androgenic progestins. * **Prader Staging:** Used to describe the degree of virilization of external genitalia in females. * **Steroid Sulphatase Deficiency Key Clue:** "Low estriol in a pregnant female with a post-dated pregnancy and fish-scale skin (ichthyosis) in the male newborn."

Endocrinology Flashcard 1 of 5

Question: Side effects of GH in children include raised IC pressure, Increased risk of T2DM, _____ and scoliosis

Answer: Slipped epiphysis

Endocrinology Flashcard 2 of 5

Question: Precocious puberty is defined as the onset of secondary sexual characteristics before the age of _____ years in girls and 9 years in boys.

Answer: 8

Endocrinology Flashcard 3 of 5

Question: _____ syndrome is characterized by unilateral caf-au-lait spots (coast of maine appearance), precocious puberty, and polyostotic fibrous dysplasia

Answer: McCune-Albright

Endocrinology Flashcard 4 of 5

Question: Thyroid, Pituitary, & Adrenal _____ is a hormone that may be used for treatment of Turner syndrome, which is characterized by an XO genotype

Answer: Growth hormone

Endocrinology Flashcard 5 of 5

Question: Pseudohypoparathyroidism type 1a or Albright hereditary osteodystrophy is characterized by shortened stature and shortened _____ and 5th digits

Answer: 4th