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: Screening of neonatal thyroid disease is done by?

• A. T4
• B. T3
• C. TSH (Correct Answer)
• D. TPO antibodies

Endocrinology Explanation: **Explanation:** **1. Why TSH is the Correct Answer:** Congenital Hypothyroidism (CH) is one of the most common preventable causes of intellectual disability. The primary screening strategy worldwide, including India, is the measurement of **Thyroid Stimulating Hormone (TSH)**. * **Sensitivity:** TSH is the most sensitive indicator for detecting **Primary Congenital Hypothyroidism** (which accounts for >95% of cases). Even a slight decrease in thyroid hormone production leads to a significant compensatory rise in TSH. * **Timing:** Screening is ideally performed between **48 to 72 hours of life**. This avoids the "physiological TSH surge" that occurs immediately after birth, which can lead to false-positive results. **2. Why Other Options are Incorrect:** * **T4 (Thyroxine):** While some programs use a "Primary T4 with reflex TSH" approach, T4 alone is less specific. It can be low in premature infants or those with TBG (Thyroid Binding Globulin) deficiency, leading to false positives. * **T3 (Triiodothyronine):** T3 levels are often the last to fall in hypothyroidism and can remain normal even in severe cases due to increased peripheral conversion of T4 to T3. It has no role in screening. * **TPO Antibodies:** These are markers for autoimmune thyroiditis (e.g., Hashimoto’s), which is an acquired condition and not a cause of congenital hypothyroidism. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of CH:** Thyroid Dysgenesis (Ectopy is the most common specific type). * **Most common clinical feature:** Most neonates are **asymptomatic** at birth. If present, early signs include a large posterior fontanelle, prolonged physiological jaundice, and umbilical hernia. * **Sample collection:** Done via **heel prick** on a Guthrie card (filter paper). * **Treatment:** Levothyroxine (10–15 μg/kg/day) should be started immediately, ideally within the first 2 weeks of life, to ensure normal neurodevelopment.

Endocrinology Indian Medical PG Question 5: 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 6: 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 Indian Medical PG Question 7: What is the drug of choice for a pregnant female suspected of having a baby with congenital adrenal hyperplasia?

• A. Dexamethasone (Correct Answer)
• B. Betamethasone
• C. Hydrocortisone
• D. Prednisolone

Endocrinology Explanation: ### Explanation **1. Why Dexamethasone is the Correct Answer:** The primary goal in treating a fetus suspected of having **Congenital Adrenal Hyperplasia (CAH)**—specifically 21-hydroxylase deficiency—is to prevent the **virilization (masculinization)** of a female fetus. Dexamethasone is the drug of choice because it is **not inactivated by the placental enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)**. Unlike most other steroids, Dexamethasone crosses the placenta in its active form, reaches the fetal circulation, and suppresses the fetal pituitary ACTH. This reduces the overproduction of adrenal androgens, thereby preventing ambiguous genitalia in females. Treatment must be started early (before the 9th week of gestation) to be effective. **2. Why Other Options are Incorrect:** * **Betamethasone:** While it also crosses the placenta (used for fetal lung maturity), Dexamethasone is the established standard of care in clinical protocols for CAH prenatal management. * **Hydrocortisone & Prednisolone:** These are the drugs of choice for treating CAH *after* birth. However, during pregnancy, they are **extensively metabolized/inactivated by the placental 11β-HSD2 enzyme**. Consequently, they do not reach the fetus in sufficient concentrations to suppress the fetal adrenal gland. **3. NEET-PG High-Yield Pearls:** * **Timing:** Treatment must begin as soon as pregnancy is confirmed, ideally by the **6th–7th week**, before the sex of the fetus is known. * **Diagnosis:** If the fetus is later determined to be male (via CVS or amniocentesis) or an unaffected female, Dexamethasone is discontinued to avoid unnecessary steroid exposure. * **Enzyme Deficiency:** 21-hydroxylase deficiency is the most common cause of CAH (>90%), leading to low cortisol and high 17-OH Progesterone. * **Side Effects:** Maternal side effects of prenatal dexamethasone include weight gain, striae, and gestational diabetes.

Endocrinology Indian Medical PG Question 8: Which of the following enzyme deficiencies is the most common cause of pseudohermaphroditism in a female child?

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

Endocrinology Explanation: **Explanation:** The correct answer is **21-hydroxylase deficiency**, which accounts for approximately **90-95% of all cases of Congenital Adrenal Hyperplasia (CAH)**. **Why 21-hydroxylase deficiency is correct:** In this condition, a block in the 21-hydroxylation pathway prevents the conversion of Progesterone to Deoxycorticosterone and 17-OH Progesterone to 11-Deoxycortisol. This leads to a deficiency in **Cortisol** and **Aldosterone**. The resulting lack of negative feedback causes an increase in ACTH, which shunts steroid precursors toward the **androgen pathway**. In a female fetus (46, XX), these excess androgens cause virilization of the external genitalia (clitoromegaly, labial fusion), leading to **female pseudohermaphroditism** (ambiguous genitalia with normal internal female organs). **Why the other options are incorrect:** * **11-hydroxylase deficiency:** This is the second most common cause (5%). While it also causes virilization, it is uniquely characterized by **hypertension** due to the accumulation of 11-deoxycorticosterone (a mineralocorticoid). * **17-hydroxylase deficiency:** This leads to a decrease in both cortisol and sex hormones. It causes **delayed puberty** and hypertension, but it does *not* cause virilization; rather, it leads to phenotypically female appearances in males. * **3-beta-hydroxysteroid dehydrogenase deficiency:** This is a rare form that affects all classes of adrenal and gonadal steroids, usually resulting in incomplete virilization in males and mild virilization in females. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** Elevated levels of **17-hydroxyprogesterone (17-OHP)**. * **Classic Presentation:** Salt-wasting crisis (hyponatremia, hyperkalemia, hypotension) usually occurs in the 2nd week of life. * **Management:** Glucocorticoid (Hydrocortisone) to suppress ACTH and Fludrocortisone for salt-wasting. * **Karyotype:** Always 46, XX in female pseudohermaphroditism.

Endocrinology Indian Medical PG Question 9: About Cushing syndrome, all are true except:

• A. Purple striae
• B. Plethora
• C. Hypoglycemia (Correct Answer)
• D. Obesity

Endocrinology Explanation: **Explanation:** Cushing syndrome is characterized by a state of chronic **hypercortisolism**. To identify the correct answer, one must understand the physiological actions of cortisol on metabolism and physical appearance. **Why Hypoglycemia is the Correct Answer (The "Except"):** Cortisol is a potent **glucocorticoid** and a counter-regulatory hormone. It increases blood glucose levels by stimulating gluconeogenesis in the liver and decreasing peripheral glucose uptake (anti-insulin effect). Therefore, Cushing syndrome typically presents with **hyperglycemia** or impaired glucose tolerance, not hypoglycemia. **Analysis of Other Options:** * **Obesity (Option D):** This is the most common clinical feature. It is typically "centripetal," involving the face (moon facies), neck (buffalo hump), and trunk, while sparing the extremities. * **Purple Striae (Option A):** Excess cortisol inhibits collagen synthesis and causes protein catabolism. This leads to thinning of the skin and rupture of dermal elastic fibers, resulting in wide (>1 cm), reddish-purple striae, usually on the abdomen and thighs. * **Plethora (Option B):** Facial plethora (redness) occurs due to the thinning of the dermis and underlying telangiectasia, making the subepidermal vascularity more visible. **NEET-PG High-Yield Pearls:** * **Most common cause overall:** Iatrogenic (exogenous steroid use). * **Most common endogenous cause (Pediatrics):** Adrenal tumors (especially in children <7 years); Cushing Disease (pituitary adenoma) is more common in adolescents. * **Screening Tests:** 24-hour urinary free cortisol, Overnight Dexamethasone Suppression Test (ODST), or Late-night salivary cortisol. * **Metabolic Profile:** Hypernatremia, **Hypokalemia**, and Metabolic Alkalosis (due to mineralocorticoid effects of high cortisol).

Endocrinology Indian Medical PG Question 10: A girl presents with hyperpigmented skin lesions, precocious puberty, and bony lesions. What is the most probable diagnosis?

• A. Cushing syndrome
• B. Neurofibromatosis
• C. McCune-Albright syndrome (Correct Answer)
• D. Hypothalamic hamartoma

Endocrinology Explanation: ### Explanation **McCune-Albright Syndrome (MAS)** is the correct diagnosis based on the classic clinical triad presented: 1. **Hyperpigmented skin lesions:** Characterized by "Café-au-lait" spots with irregular borders (often described as the **"Coast of Maine"** appearance). 2. **Precocious Puberty:** Specifically **GnRH-independent (peripheral)** precocious puberty, caused by autonomous functioning of the ovaries. 3. **Bony lesions:** Known as **Polyostotic Fibrous Dysplasia**, where normal bone is replaced by fibrous tissue, leading to fractures and deformities. **Pathophysiology:** The condition is caused by a somatic (post-zygotic) mutation in the **GNAS gene**, which encodes the alpha subunit of the **Gs protein**. This leads to constitutive activation of adenylate cyclase, causing overproduction of cAMP and subsequent overactivity in various endocrine tissues (ovaries, thyroid, adrenals, and pituitary). --- ### Why the other options are incorrect: * **Cushing Syndrome:** While it involves endocrine dysfunction, it typically presents with weight gain, moon facies, and striae, rather than precocious puberty or fibrous dysplasia. * **Neurofibromatosis (Type 1):** Also features Café-au-lait spots, but they have smooth borders (**"Coast of California"**) and are associated with neurofibromas and Lisch nodules, not precocious puberty or polyostotic fibrous dysplasia. * **Hypothalamic Hamartoma:** This is the most common cause of **central (GnRH-dependent)** precocious puberty. It does not present with skin pigmentation or bony lesions. --- ### High-Yield Clinical Pearls for NEET-PG: * **Inheritance:** It is **not inherited**; it occurs due to a sporadic somatic mutation. If the mutation were germline, it would be lethal. * **Gender:** More common in girls. * **Management:** For precocious puberty in MAS, **Letrozole** (aromatase inhibitor) or **Tamoxifen** (SERM) are often used to block estrogen effects. * **Radiology:** Fibrous dysplasia on X-ray shows a characteristic **"Ground-glass" appearance**.

Endocrinology Flashcard 1 of 10

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

Answer: Slipped epiphysis

Endocrinology Flashcard 2 of 10

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 10

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 4 of 10

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 5 of 10

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

Answer: 4th

Endocrinology Flashcard 6 of 10

Question: _____ syndrome, also known as dwarfism, is due to defective growth hormone receptors, causing decreased linear growth

Answer: Laron

Endocrinology Flashcard 7 of 10

Question: In childhood, hormone levels are _____ and FSH levels are greater than LH levels

Answer: lowest

Endocrinology Flashcard 8 of 10

Question: What is the effect of cryptorchidism on fertility? Why? _____

Answer: Decreased

Endocrinology Flashcard 9 of 10

Question: Acute suppurative thyroiditis mimics De Quervains thyroiditis but it is more common in _____.

Answer: children

Endocrinology Flashcard 10 of 10

Question: In _____ type of classical CAH, there is deficiency of cortisol and adequate aldosterone, with excess androgen production

Answer: simple virilizing