Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 71: A female child presents with ambiguous genitalia and hyperpigmentation of the skin. She has increased blood pressure and hypokalemia. Which of the following enzymes is deficient in this child?

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

Explanation: ### Explanation The clinical presentation of **ambiguous genitalia** in a female child (virilization) combined with **hypertension** and **hypokalemia** is diagnostic of **11β-hydroxylase deficiency**, the second most common cause of Congenital Adrenal Hyperplasia (CAH). **1. Why 11β-hydroxylase is correct:** A deficiency in this enzyme blocks the conversion of 11-deoxycortisol to cortisol and 11-deoxycorticosterone (DOC) to corticosterone. This leads to: * **Androgen Excess:** Shunting of precursors into the androgen pathway causes virilization (ambiguous genitalia in females). * **Mineralocorticoid Excess:** While aldosterone is low, there is a massive buildup of **11-deoxycorticosterone (DOC)**. DOC is a potent mineralocorticoid that causes sodium retention and potassium excretion, leading to **hypertension** and **hypokalemia**. * **Hyperpigmentation:** Low cortisol leads to increased ACTH, which stimulates melanocytes. **2. Why other options are incorrect:** * **21-hydroxylase deficiency:** The most common CAH. It causes virilization but presents with **hypotension** (salt-wasting) and **hyperkalemia** due to a total lack of mineralocorticoids. * **17α-hydroxylase deficiency:** Presents with hypertension and hypokalemia, but results in a **lack of sex hormones**. This causes delayed puberty or primary amenorrhea in females, not ambiguous genitalia. * **17, 20 Lyase deficiency:** Affects only sex hormone synthesis. It leads to a lack of androgens (undervirilization in males) but does not affect mineralocorticoids or cause hypertension. **Clinical Pearls for NEET-PG:** * **Rule of "1":** If the enzyme starts with **1** (11β or 17α), it causes **Hypertension**. * **Rule of "Virilization":** If the enzyme ends with **1** (11β or 21), it causes **Virilization** in females. * **11β-hydroxylase** is unique because it is the only CAH that causes **both** virilization and hypertension.

Question 72: An abnormally tall 11-year-old child with normal mentation is most likely to have which of the following syndromes?

A. Sotos syndrome
B. Homocystinuria
C. XXY syndrome
D. Marfan syndrome (Correct Answer)

Explanation: **Explanation:** The clinical presentation of an abnormally tall child with **normal mentation** (intelligence) is a classic descriptor for **Marfan Syndrome**. 1. **Marfan Syndrome (Correct):** This is an autosomal dominant connective tissue disorder caused by a mutation in the **FBN1 gene** (Fibrillin-1) on Chromosome 15. Key features include arachnodactyly, a high arm span-to-height ratio (>1.05), and ectopia lentis (typically upward lens subluxation). Crucially, patients with Marfan syndrome have **normal intelligence**, which distinguishes it from several other overgrowth syndromes. 2. **Why other options are incorrect:** * **Sotos Syndrome:** Also known as "Cerebral Gigantism," it presents with rapid growth and a characteristic facial appearance (macrodolichocephaly). However, it is almost always associated with **intellectual disability** and developmental delay. * **Homocystinuria:** While it mimics Marfanoid habitus (tall stature, lens dislocation), it is characterized by **intellectual disability** and a high risk of thromboembolic events. The lens dislocation is typically downward (inferonasal). * **XXY Syndrome (Klinefelter Syndrome):** While these patients are tall, they often present with mild cognitive impairment, learning disabilities, and behavioral issues, alongside hypogonadism post-puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Marfan vs. Homocystinuria:** Marfan = Upward lens subluxation + Normal IQ. Homocystinuria = Downward lens subluxation + Low IQ + Thrombosis. * **Most common cause of death in Marfan:** Aortic root dilatation leading to aortic dissection or mitral valve prolapse (MVP). * **Sotos Syndrome marker:** Mutation in the **NSD1 gene**. * **Screening:** All children with suspected Marfan syndrome must undergo an **Echocardiogram** and a slit-lamp examination.

Question 73: Which of the following conditions affects only males?

A. Scheie's syndrome
B. Hunter's syndrome (Correct Answer)
C. Hurler's syndrome
D. Gaucher's disease

Explanation: **Explanation:** The correct answer is **Hunter’s syndrome (Mucopolysaccharidosis Type II)**. The key to solving this question lies in understanding the **mode of inheritance**. Hunter’s syndrome is the only Mucopolysaccharidosis (MPS) that is inherited in an **X-linked recessive** manner. Because males have only one X chromosome, they are primarily affected, while females are typically asymptomatic carriers. It is caused by a deficiency of the enzyme **Iduronate-2-sulfatase**, leading to the accumulation of dermatan and heparan sulfate. **Analysis of Incorrect Options:** * **Hurler’s syndrome (MPS I) and Scheie’s syndrome (MPS IS):** Both are caused by a deficiency of **Alpha-L-iduronidase**. They are inherited in an **Autosomal Recessive** pattern, meaning they affect males and females equally. Hurler’s is the most severe form, while Scheie’s is the mildest. * **Gaucher’s disease:** This is a lysosomal storage disorder caused by a deficiency of **Glucocerebrosidase**. It is also inherited in an **Autosomal Recessive** pattern, affecting both sexes. **High-Yield Clinical Pearls for NEET-PG:** 1. **The "No Clouding" Rule:** A classic clinical differentiator is that **Hunter’s syndrome has NO corneal clouding**, whereas Hurler’s syndrome does. (Mnemonic: *The Hunter needs clear vision to see his target*). 2. **Clinical Features:** Look for coarse facial features, hepatosplenomegaly, joint stiffness, and "pebbly" skin lesions (scapular region). 3. **X-linked Recessive Disorders in Pediatrics:** Other high-yield examples include Duchenne Muscular Dystrophy, Hemophilia A/B, G6PD deficiency, and Lesch-Nyhan syndrome.

Question 74: A child presents with stunted growth, a protuberant abdomen, short stature, and mental retardation. Deficiency of which of the following is the most likely cause?

A. Thyroxine (Correct Answer)
B. Growth hormone
C. Vitamin D
D. Parathyroid hormone

Explanation: The clinical presentation described is a classic case of **Congenital Hypothyroidism (Cretinism)**. ### **Why Thyroxine is the Correct Answer** Thyroxine ($T_4$) is essential for the normal development of the skeletal system and the central nervous system during infancy. Deficiency leads to: * **Mental Retardation:** Thyroid hormones are critical for myelination and neuronal migration in the brain. * **Stunted Growth & Short Stature:** Due to impaired bone maturation and delayed epiphyseal closure. * **Protuberant Abdomen:** Caused by hypotonia of the abdominal muscles and often associated with an umbilical hernia and constipation. * **Other features:** Macroglossia (large tongue), coarse facies, and prolonged neonatal jaundice. ### **Why Other Options are Incorrect** * **Growth Hormone (GH):** GH deficiency causes "Pituitary Dwarfism." While it leads to short stature and a "doll-like" face, it **does not** cause mental retardation or a protuberant abdomen. * **Vitamin D:** Deficiency causes Rickets. While it can cause a "pot-belly" (due to hypotonia) and growth retardation, it is not typically associated with mental retardation. * **Parathyroid Hormone (PTH):** Deficiency (Hypoparathyroidism) leads to hypocalcemia, tetany, and seizures, but not the classic triad of cretinism. ### **NEET-PG High-Yield Pearls** * **Most common cause of Congenital Hypothyroidism:** Thyroid dysgenesis (Ectopy is the most common specific type). * **Most common preventable cause of mental retardation:** Congenital Hypothyroidism. * **Early Sign:** A posterior fontanelle >0.5 cm in a newborn should raise suspicion. * **Diagnosis:** Best screened via **TSH levels** (usually >20 mU/L) in the neonatal period. * **Treatment:** Levothyroxine must be started within the first 2 weeks of life to prevent permanent neurocognitive deficits.

Question 75: Precocious puberty is seen in all except?

A. Tumor of the hypothalamus
B. Ovarian tumor
C. Tumor of the adrenal gland
D. None of the above (Correct Answer)

Explanation: **Explanation:** Precocious puberty is defined as the onset of secondary sexual characteristics before the age of 8 in girls and 9 in boys. It is broadly classified into **Central (GnRH-dependent)** and **Peripheral (GnRH-independent)** precocious puberty. The correct answer is **"None of the above"** because all the listed conditions (A, B, and C) are established causes of precocious puberty. * **Option A: Tumor of the Hypothalamus:** This causes **Central Precocious Puberty**. Lesions such as hypothalamic hamartomas, optic gliomas, or astrocytomas trigger the premature activation of the Hypothalamic-Pituitary-Gonadal (HPG) axis, leading to early gonadotropin release. * **Option B: Ovarian Tumor:** This causes **Peripheral Precocious Puberty** (Pseudoprecocity). Estrogen-secreting tumors, such as Granulosa cell tumors, lead to feminization and breast development independent of the HPG axis. * **Option C: Tumor of the Adrenal Gland:** This also causes **Peripheral Precocious Puberty**. Adrenocortical tumors can secrete excess androgens (leading to virilization in boys or girls) or estrogens, causing premature sexual development. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** In girls, central precocious puberty is usually **idiopathic** (80-90%). In boys, it is more likely to be due to a **CNS lesion** (up to 75%). * **McCune-Albright Syndrome:** A classic triad of peripheral precocious puberty, café-au-lait spots (irregular "Coast of Maine" borders), and polyostotic fibrous dysplasia. * **Bone Age:** In all forms of precocious puberty, bone age is typically **advanced** beyond the chronological age, which can lead to short adult stature due to early epiphyseal closure. * **Treatment:** GnRH analogs (e.g., Leuprolide) are the gold standard for Central Precocious Puberty.

Question 76: What is the most common gene involved in Noonan syndrome?

A. PTCN11
B. PTPN11 (Correct Answer)
C. PTPN22
D. PTCN22

Explanation: **Explanation:** **Noonan Syndrome** is an autosomal dominant disorder characterized by short stature, congenital heart defects, and distinct facial features. It is often referred to as the "Male Turner Syndrome," though it affects both sexes and has a normal karyotype. 1. **Why PTPN11 is correct:** The most common genetic cause of Noonan Syndrome (occurring in approximately **50% of cases**) is a germline mutation in the **PTPN11** gene located on chromosome 12. This gene encodes **SHP-2**, a protein tyrosine phosphatase that plays a critical role in the **RAS-MAPK signaling pathway**. Mutations in this pathway (collectively called "RASopathies") lead to gain-of-function signaling, resulting in the clinical manifestations of the syndrome. 2. **Analysis of Incorrect Options:** * **PTCN11 & PTCN22:** These are distractor options with incorrect prefixes. There are no major clinical syndromes associated with genes by these names in standard medical literature. * **PTPN22:** While this gene belongs to the same family, it is primarily associated with an increased risk of **autoimmune diseases** (such as Type 1 Diabetes, Rheumatoid Arthritis, and SLE) rather than developmental syndromes like Noonan. **High-Yield Clinical Pearls for NEET-PG:** * **Cardiac Findings:** The most common cardiac lesion is **Pulmonary Stenosis** (dysplastic valve), followed by Hypertrophic Cardiomyopathy (HCM). * **Facial Features:** Hypertelorism, downward slanting palpebral fissures, low-set posteriorly rotated ears, and a webbed neck. * **Hematology:** Patients often have a predisposition to bleeding diathesis and **Juvenile Myelomonocytic Leukemia (JMML)**. * **Differential:** Unlike Turner Syndrome (45,XO), Noonan patients are usually fertile (though males may have cryptorchidism) and have a normal 46,XX or 46,XY karyotype.

Question 77: Precocious puberty and patchy skin pigmentation are known to occur in which condition?

A. McCune Albright syndrome (Correct Answer)
B. Letterer-Siwe disease
C. Asherman's syndrome
D. Morquio's syndrome

Explanation: **McCune-Albright Syndrome (MAS)** is the correct answer because it is classically defined by a clinical triad: **Peripheral Precocious Puberty**, **Café-au-lait skin pigmentation**, and **Polyostotic Fibrous Dysplasia**. ### 1. Why McCune-Albright Syndrome is Correct The underlying pathophysiology is a post-zygotic somatic mutation in the **GNAS gene**, which leads to constitutive activation of the **Gs-alpha protein**. This results in overproduction of cAMP, causing autonomous hyperfunction of endocrine glands. In females, this manifests as recurrent ovarian cysts and estrogen secretion, leading to gonadotropin-independent (peripheral) precocious puberty. The skin lesions are typically large, irregular café-au-lait spots with "jagged" borders (resembling the **Coast of Maine**), usually stopping at the midline. ### 2. Why Other Options are Incorrect * **Letterer-Siwe Disease:** This is a severe, systemic form of Langerhans Cell Histiocytosis (LCH). While it presents with skin rashes (seborrheic-like), it involves hepatosplenomegaly and bone marrow infiltration, not precocious puberty. * **Asherman’s Syndrome:** This refers to intrauterine adhesions (scarring) usually following D&C. It causes secondary amenorrhea and infertility, the opposite of precocious puberty. * **Morquio’s Syndrome:** A type of Mucopolysaccharidosis (MPS IV) characterized by severe skeletal dysplasia and short stature, but it does not involve precocious puberty or specific patchy pigmentation. ### 3. NEET-PG High-Yield Pearls * **Triad:** Fibrous dysplasia + Café-au-lait spots + Precocious puberty. * **Mutation:** GNAS1 gene (Somatic mosaicism). * **Skin:** "Coast of Maine" (irregular) vs. Neurofibromatosis "Coast of California" (smooth). * **Endocrine:** Can also cause hyperthyroidism, GH excess (acromegaly), and Cushing syndrome.

Question 78: A child presents with learning disabilities. On examination, horseshoe kidney and streak gonads are noted. What is your diagnosis?

A. Klinefelter's syndrome
B. Noonan's syndrome
C. Turner's syndrome (Correct Answer)
D. Fragile-X syndrome

Explanation: **Explanation:** The clinical triad of **learning disabilities, horseshoe kidney, and streak gonads** is a classic presentation of **Turner’s Syndrome (45, XO)**. **Why Turner’s Syndrome is Correct:** Turner’s syndrome occurs due to complete or partial monosomy of the X chromosome. * **Streak Gonads:** The absence of the second X chromosome leads to accelerated oocyte atresia, replacing normal ovarian tissue with fibrous "streak" tissue, resulting in primary amenorrhea and hypergonadotropic hypogonadism. * **Horseshoe Kidney:** This is the most common renal anomaly in Turner’s (seen in ~10-15% of cases). * **Neuropsychiatric features:** While global IQ is usually normal, these children often face specific learning disabilities, particularly in visuospatial processing and mathematics. **Why Other Options are Incorrect:** * **Klinefelter’s Syndrome (47, XXY):** Presents in males with small, firm testes, gynecomastia, and tall stature. They do not have streak gonads or a high incidence of horseshoe kidneys. * **Noonan’s Syndrome:** Often called "Male Turner’s" due to similar features (webbed neck, short stature), but it is autosomal dominant. Key differentiators: it affects both sexes, features **Right-sided** heart defects (Pulmonary Stenosis), and patients usually have **normal** gonads/fertility. * **Fragile-X Syndrome:** The most common cause of inherited intellectual disability in males. Characterized by macro-orchidism (large testes), not streak gonads. **High-Yield Clinical Pearls for NEET-PG:** * **Most common Cardiac Anomaly:** Bicuspid Aortic Valve (overall); Coarctation of Aorta (classic association). * **Lymphedema:** Present at birth (hand/foot swelling) due to lymphatic hypoplasia. * **Short Stature:** Attributed to the loss of the **SHOX gene**. * **Dermatoglyphics:** Increased total ridge count on fingertips.

Question 79: Which clinical features are characteristic of congenital adrenal hyperplasia?

A. Female pseudohermaphroditism
B. Hypertension
C. Electrolyte imbalance
D. All of the above (Correct Answer)

Explanation: **Explanation:** Congenital Adrenal Hyperplasia (CAH) is a group of autosomal recessive disorders caused by a deficiency in enzymes required for cortisol synthesis. The clinical features depend on which enzyme is deficient, but the most common form is **21-Hydroxylase deficiency (90% of cases)**. 1. **Female Pseudohermaphroditism (Option A):** In 21-Hydroxylase deficiency, the blockage of the cortisol pathway shunts precursors toward androgen production. Excess androgens in utero lead to virilization of female fetuses (ambiguous genitalia/clitoromegaly), while chromosomal sex remains 46,XX. 2. **Hypertension (Option B):** While the most common form (21-OH deficiency) causes hypotension, the **11β-Hydroxylase** and **17α-Hydroxylase** deficiencies lead to an accumulation of 11-deoxycorticosterone (DOC), a potent mineralocorticoid that causes fluid retention and hypertension. 3. **Electrolyte Imbalance (Option C):** In the "salt-wasting" form of 21-Hydroxylase deficiency, aldosterone deficiency leads to **hyponatremia, hyperkalemia, and metabolic acidosis**. Since CAH encompasses various enzymatic defects that can present with any of these features, **"All of the above"** is the correct choice. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Enzyme Deficiency:** 21-Hydroxylase (Check for elevated **17-Hydroxyprogesterone**). * **The "1" Rule for Hypertension:** If the enzyme starts with '1' (11β-OH or 17α-OH), hypertension is present. * **The "1" Rule for Virilization:** If the enzyme ends with '1' (21-OH or 11β-OH), virilization/ambiguous genitalia occurs in females. * **Gold Standard Treatment:** Glucocorticoid replacement (e.g., Hydrocortisone) to suppress ACTH and reduce androgen overproduction.

Question 80: Delayed puberty is seen in all except?

A. Chronic disease
B. Hypothyroidism
C. Turner's syndrome
D. McCune-Albright syndrome (Correct Answer)

Explanation: **Explanation:** The core concept in this question is distinguishing between causes of **delayed puberty** versus **precocious puberty**. **Why McCune-Albright Syndrome (MAS) is the correct answer:** McCune-Albright syndrome is a classic cause of **Peripheral Precocious Puberty** (GnRH-independent). It is caused by a somatic mutation in the *GNAS1* gene, leading to constitutive activation of the G-protein signaling pathway. This results in the triad of: 1. **Precocious puberty** (due to autonomous endocrine hyperfunction, usually ovarian cysts in girls). 2. **Polyostotic fibrous dysplasia.** 3. **Café-au-lait spots** (typically with irregular "Coast of Maine" borders). Because it causes early onset of puberty, it is the "except" in this list. **Analysis of Incorrect Options (Causes of Delayed Puberty):** * **Chronic Disease (Option A):** Conditions like Celiac disease, Chronic Kidney Disease, or Cystic Fibrosis cause functional gonadotropin deficiency due to chronic stress and malnutrition, leading to delayed puberty. * **Hypothyroidism (Option B):** While severe primary hypothyroidism can rarely cause Van Wyk-Grumbach syndrome (pseudoprecocity), it is a well-established cause of **growth failure and delayed bone age**, which typically manifests as delayed onset of true puberty. * **Turner’s Syndrome (Option C):** This is a form of **Hypergonadotropic Hypogonadism**. Due to streak ovaries (gonadal dysgenesis), there is a lack of estrogen feedback, leading to elevated FSH/LH but a failure to initiate or progress through puberty. **NEET-PG High-Yield Pearls:** * **Definition:** Delayed puberty is the absence of secondary sexual characteristics by age **13 in girls** (no breast development) and **14 in boys** (testicular volume <4ml). * **Most common cause:** Constitutional Delay of Growth and Puberty (CDGP) – characterized by delayed bone age but a normal final height. * **Kallmann Syndrome:** A key cause of Hypogonadotropic Hypogonadism associated with **anosmia**.

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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