Endocrinology — MCQs
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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?
Deep white matter lesion with bilateral deep bright thalamic appearance is suggestive of which condition?
Cretinism is characterized by which of the following physical features?
Which of the following is a manifestation of 22q11 deletion syndrome?
What is the least common cause of ambiguous genitalia in a female genotype?
About Cushing syndrome, all are true except:
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?
A 13-year-old boy presents with bilateral gynecomastia. His height is 148 cm, weight is 58 kg, and his sexual maturity rating is stage 2. The gynecomastia is most likely due to what condition?
Which of the following drugs is not used for the therapy of congenital adrenal hyperplasia?
All of the following conditions except one can lead to delayed puberty?
Endocrinology Indian Medical PG Practice Questions and MCQs
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
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.
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
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).
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
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.
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
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.
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
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."
Question 6: About Cushing syndrome, all are true except:
- A. Purple striae
- B. Plethora
- C. Hypoglycemia (Correct Answer)
- D. Obesity
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).
Question 7: 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?
- A. Congenital adrenal hyperplasia due to 21-alpha hydroxylase deficiency
- B. Familial glucocorticoid deficiency (Correct Answer)
- C. Cushing syndrome
- D. Insulinoma
Explanation: **Explanation:** The clinical presentation of a 6-week-old infant with **hypoglycemia** (30 mg/dl) and **increased skin pigmentation** (hyperpigmentation) suggests primary adrenal insufficiency. The presence of hyperpigmentation indicates elevated ACTH levels (due to lack of negative feedback), which stimulates melanocytes. **1. Why Familial Glucocorticoid Deficiency (FGD) is correct:** FGD is a rare autosomal recessive disorder characterized by **isolated glucocorticoid deficiency** due to resistance to ACTH (often mutations in the MC2R receptor). * **Hypoglycemia:** Occurs due to the lack of cortisol, a counter-regulatory hormone. * **Hyperpigmentation:** Caused by compensatory high ACTH levels. * **Normal BP and Genitalia:** Unlike other adrenal disorders, mineralocorticoid (aldosterone) levels are normal, so there is no salt-wasting or hypotension. There is no excess androgen production, so genitalia appear normal. **2. Why other options are incorrect:** * **21-α Hydroxylase Deficiency (CAH):** This is the most common cause of CAH. While it causes hypoglycemia and hyperpigmentation, it typically presents with **ambiguous genitalia** in females (virilization) and **salt-wasting crises** (hypotension, hyponatremia, hyperkalemia), which are absent here. * **Cushing Syndrome:** Characterized by glucocorticoid *excess*, leading to hyperglycemia and weight gain, not hypoglycemia. * **Insulinoma:** Causes profound hypoglycemia but would not cause skin hyperpigmentation. **Clinical Pearls for NEET-PG:** * **Isolated Glucocorticoid Deficiency:** Think FGD if there is hypoglycemia + hyperpigmentation + **normal electrolytes/BP**. * **ACTH & Pigmentation:** ACTH is derived from POMC (Pro-opiomelanocortin). High ACTH leads to high α-MSH (Melanocyte Stimulating Hormone), causing darkening of skin/mucosa. * **Hypoglycemia in Infancy:** Always evaluate for "Critical Samples" (Cortisol, Growth Hormone, Insulin, and Ketones) during the hypoglycemic episode.
Question 8: A 13-year-old boy presents with bilateral gynecomastia. His height is 148 cm, weight is 58 kg, and his sexual maturity rating is stage 2. The gynecomastia is most likely due to what condition?
- A. Prolactinoma
- B. Testicular tumor
- C. Pubertal gynecomastia (Correct Answer)
- D. Chronic liver disease
Explanation: **Explanation:** **Pubertal gynecomastia** is the most common cause of breast enlargement in adolescent males, affecting up to 50–60% of boys during puberty. It typically occurs between ages 10 and 14, corresponding to **Sexual Maturity Rating (SMR/Tanner) stages 2 or 3**. The underlying pathophysiology is a **transient imbalance** between estrogen and androgen action at the breast tissue level, where estrogen levels rise earlier or more rapidly than testosterone during early puberty. In most cases, it is bilateral, benign, and resolves spontaneously within 6 to 24 months. **Why other options are incorrect:** * **Prolactinoma:** While hyperprolactinemia can cause galactorrhea, it rarely causes true gynecomastia unless it leads to secondary hypogonadism (low testosterone). * **Testicular Tumor:** Certain tumors (e.g., Leydig cell or hCG-secreting germ cell tumors) can cause gynecomastia due to excess estrogen production, but these are rare and usually present with a palpable testicular mass or rapid virilization. * **Chronic Liver Disease:** This causes gynecomastia via decreased degradation of androstenedione and increased peripheral conversion to estrogen. However, it would be accompanied by other systemic signs like jaundice, hepatosplenomegaly, or spider nevi. **NEET-PG High-Yield Pearls:** * **Peak Incidence:** Tanner Stage 2–3. * **Management:** Reassurance is the first line. Medical therapy (Tamoxifen) or surgery is only considered if it persists beyond age 17, causes severe psychological distress, or is macrogynecomastia (>5 cm). * **Drugs causing gynecomastia (Mnemonic: DISCO):** **D**igoxin, **I**soniazid, **S**pironolactone, **C**imetidine, **O**estrogens/Ketoconazole.
Question 9: Which of the following drugs is not used for the therapy of congenital adrenal hyperplasia?
- A. Hydrocortisone
- B. Prednisolone
- C. Antibiotics (Correct Answer)
- D. Dexamethasone
Explanation: **Explanation:** **Congenital Adrenal Hyperplasia (CAH)** is a group of autosomal recessive disorders characterized by a deficiency in enzymes required for cortisol synthesis (most commonly **21-hydroxylase deficiency**). The primary goal of therapy is to replace the deficient hormones and suppress the excess production of CRH and ACTH, which drive adrenal androgen excess. **Why Antibiotics is the Correct Answer:** Antibiotics have no role in the pathophysiology or standard management of CAH. CAH is an endocrine/genetic disorder, not an infectious one. While a patient with CAH might require antibiotics for a concurrent infection, they are not a "therapy for CAH" itself. **Analysis of Incorrect Options (Drugs used in CAH):** * **Hydrocortisone:** This is the **drug of choice** in growing children. It has a short half-life, which minimizes growth suppression while providing necessary glucocorticoid replacement and ACTH suppression. * **Prednisolone:** This is a longer-acting glucocorticoid. It is generally reserved for adolescents who have completed their linear growth or for cases where hydrocortisone fails to achieve adequate control. * **Dexamethasone:** This is a potent, long-acting glucocorticoid. It is avoided in growing children due to its profound effect on growth plates but may be used in adults or for **prenatal treatment** (administered to the mother) to prevent virilization in a female fetus. **NEET-PG High-Yield Pearls:** * **Most common cause:** 21-hydroxylase deficiency (>90% of cases). * **Diagnostic Marker:** Elevated **17-hydroxyprogesterone (17-OHP)**. * **Salt-wasting type:** Requires both glucocorticoids and mineralocorticoids (**Fludrocortisone**). * **Classic Presentation:** Ambiguous genitalia in females and salt-wasting crisis (hyponatremia, hyperkalemia, hypotension) in the neonatal period.
Question 10: All of the following conditions except one can lead to delayed puberty?
- A. Kallman syndrome
- B. McCune-Albright syndrome (Correct Answer)
- C. Turner syndrome
- D. Addison disease
Explanation: **Explanation:** The core concept in this question is differentiating between conditions that cause **delayed puberty** versus those that cause **precocious (early) puberty**. **Why McCune-Albright Syndrome (MAS) is the correct answer:** McCune-Albright Syndrome is a classic cause of **GnRH-independent (Peripheral) Precocious Puberty**. It is caused by a somatic mutation in the *GNAS1* gene, leading to constitutive activation of the G-protein signaling pathway. This results in autonomous overproduction of hormones. The clinical triad includes: 1. **Precocious puberty** (typically presenting as early vaginal bleeding in girls). 2. **Polyostotic fibrous dysplasia** (bony lesions). 3. **Café-au-lait spots** (irregular "Coast of Maine" borders). **Why the other options are incorrect:** * **Kallmann Syndrome:** A form of hypogonadotropic hypogonadism (low FSH/LH) due to failure of GnRH neuron migration. It presents with **delayed puberty** and anosmia. * **Turner Syndrome (45,XO):** The most common cause of primary amenorrhea and **delayed puberty** in females due to streak ovaries (hypergonadotropic hypogonadism). * **Addison Disease:** Chronic adrenal insufficiency can lead to significant systemic illness and nutritional compromise, which often results in a functional delay of the hypothalamic-pituitary-gonadal axis, leading to **delayed puberty**. **NEET-PG High-Yield Pearls:** * **Delayed Puberty Definition:** Absence of secondary sexual characteristics by age 13 in girls (thelarche) or age 14 in boys (testicular volume <4ml). * **McCune-Albright:** Look for the "Coast of Maine" café-au-lait spots. In contrast, Neurofibromatosis Type 1 has "Coast of California" (smooth) spots. * **Most common cause of delayed puberty:** Constitutional Delay of Growth and Puberty (CDGP) – often a "late bloomer" with a family history.
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
Practice Questions
Endocrine Emergencies
Practice Questions
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