Endocrinology Practice Questions

Q: Which genetic syndrome is characterized by obesity and mental retardation?

Prader-Willi syndrome. **Explanation:** **Prader-Willi Syndrome (PWS)** is the correct answer. It is a classic example of **genomic imprinting**, caused by the loss of expression of genes on the paternal chromosome **15q11-q13**. The clinical hallmark is a biphasic presentation: neonatal hypotonia and feeding difficulties, followed by the development of **hyperphagia** leading to early-onset **morbid obesity** in early childhood. It is the most common genetic cause of life-threatening obesity and is consistently associated with mild-to-moderate intellectual disability (mental retardation). **Analysis of Incorrect Options:** * **Turner Syndrome (45,XO):** Characterized by short stature, webbed neck, and streak ovaries. While patients may have a higher BMI, obesity and mental retardation are not defining features; most have normal intelligence. * **Fragile-X Syndrome:** The most common inherited cause of intellectual disability. While it features macroorchidism and a long face, it is not typically associated with obesity. * **Noonan Syndrome:** Often called "Male Turner Syndrome," it presents with short stature, heart defects (Pulmonic stenosis), and webbed neck. Cognitive impairment is variable, but obesity is not a primary feature. **Clinical Pearls for NEET-PG:** * **Genetic Mechanism:** PWS is due to Paternal deletion (70%), Maternal Uniparental Disomy (25%), or Imprinting defects. * **Endocrine Features:** Growth hormone deficiency (short stature) and hypogonadotropic hypogonadism (undescended testes, delayed puberty). * **Behavioral Phenotype:** Skin picking (dermatillomania) and temper tantrums. * **Contrast:** **Angelman Syndrome** ("Happy Puppet") involves the loss of the *maternal* copy of the same region (15q11-q13).

Q: Which of the following is NOT a metabolic abnormality seen in congenital adrenal hyperplasia?

Hypokalemia. **Explanation:** Congenital Adrenal Hyperplasia (CAH), most commonly due to **21-hydroxylase deficiency** (90-95% of cases), results in the impaired synthesis of cortisol and aldosterone. The absence of aldosterone leads to a "salt-wasting" state, which is the key to understanding the metabolic profile. 1. **Why Hypokalemia is the correct answer:** In CAH, the lack of aldosterone prevents the kidneys from excreting potassium and hydrogen ions in exchange for sodium. This leads to **Hyperkalemia**, not hypokalemia. Therefore, hypokalemia is the metabolic abnormality NOT seen in CAH. 2. **Analysis of incorrect options:** * **Hyponatremia (C):** Aldosterone deficiency leads to failure of sodium reabsorption in the distal renal tubules, causing significant sodium loss in the urine. * **Hypotension (A):** The combination of hyponatremia and water loss (due to osmotic diuresis) leads to volume depletion, dehydration, and eventually hypotension or hypovolemic shock. * **Metabolic Acidosis (D):** Since aldosterone is required for the secretion of $H^+$ ions into the urine, its absence results in the retention of $H^+$ ions, leading to a **normal anion gap metabolic acidosis**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common enzyme deficiency:** 21-hydroxylase deficiency (presents with virilization and salt-wasting). * **The "Exception" Rule:** In the rare **11-$\beta$-hydroxylase deficiency**, patients present with **hypertension and hypokalemia** because of the buildup of 11-deoxycorticosterone (a potent mineralocorticoid). * **Diagnostic Marker:** Elevated levels of **17-hydroxyprogesterone (17-OHP)** is the gold standard for screening/diagnosis of 21-hydroxylase deficiency. * **Clinical Presentation:** Ambiguous genitalia in females; salt-wasting crisis (vomiting, dehydration) in males at 1–2 weeks of life.

Q: What is the most common central nervous system tumor associated with precocious puberty?

Hamartoma. **Explanation:** **Correct Answer: D. Hamartoma** **Medical Concept:** Hypothalamic hamartomas are the most common CNS tumors associated with **GnRH-dependent (Central) Precocious Puberty**. These are non-neoplastic congenital malformations consisting of ectopic neural tissue (neurons and glia) located in the region of the tuber cinereum or floor of the third ventricle. They act as "ectopic GnRH pulse generators," containing neurons that autonomously secrete GnRH in a pulsatile fashion, thereby prematurely activating the pituitary-gonadal axis. **Analysis of Incorrect Options:** * **A. Astrocytoma:** While optic gliomas and hypothalamic astrocytomas (often associated with NF-1) can cause precocious puberty by disrupting inhibitory pathways to the hypothalamus, they are less common causes than hamartomas. * **B. Neurofibroma:** Neurofibromatosis Type 1 (NF-1) is associated with precocious puberty, but the underlying cause is typically an **optic pathway glioma** (astrocytoma), not a neurofibroma itself. * **C. Ependymoma:** These tumors typically arise from the lining of the ventricles. While they can cause increased intracranial pressure or hydrocephalus, they are rarely implicated as a primary cause of precocious puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Hypothalamic hamartomas are classically associated with **Gelastic Seizures** (pathognomonic "laughing" seizures), precocious puberty, and developmental delay. * **Diagnosis:** MRI is the gold standard; hamartomas appear as a pedunculated mass at the base of the hypothalamus that is isointense to gray matter on T1-weighted images and does not enhance with contrast. * **Treatment:** The drug of choice for central precocious puberty is **long-acting GnRH agonists** (e.g., Leuprolide), which desensitize the pituitary GnRH receptors.

Q: Turner syndrome - karyotyping is:

45, XO. **Explanation:** **Turner Syndrome** is the most common sex chromosomal abnormality in females, characterized by the complete or partial absence of one X chromosome. 1. **Why 45, XO is correct:** The standard karyotype for Turner syndrome is **45, XO**, indicating a total of 45 chromosomes with a single X sex chromosome and no second sex chromosome (monosomy X). This occurs due to nondisjunction during meiosis, most commonly of paternal origin. 2. **Why other options are incorrect:** * **46, XO:** This is nomenclature error. A human cell with 46 chromosomes must have two sex chromosomes (e.g., 46, XX or 46, XY). * **47, XXX:** This represents **Triple X Syndrome**, where females have an extra X chromosome. These individuals are often asymptomatic or have tall stature and learning disabilities. * **Trisomy 21:** This is the karyotype for **Down Syndrome** (47, XX/XY +21), characterized by intellectual disability and distinct facial features. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Features:** Short stature (most common feature), webbed neck (pterygium colli), widely spaced nipples (shield chest), and cubitus valgus. * **Cardiac Associations:** Bicuspid aortic valve (most common) and Coarctation of the aorta. * **Renal Association:** Horseshoe kidney. * **Gonads:** "Streak ovaries" leading to primary amenorrhea and hypergonadotropic hypogonadism. * **Genetics:** 50% are 45, XO; others may show **mosaicism (45,X/46,XX)**, which carries a higher risk for secondary amenorrhea and pregnancy. If a Y chromosome fragment is present (45,X/46,XY), there is a high risk for **Gonadoblastoma**.

Q: Nelson syndrome is seen in which of the following conditions?

Adrenalectomy. **Explanation:** **Nelson syndrome** is a clinical condition characterized by the development of an ACTH-secreting pituitary adenoma following a **bilateral adrenalectomy**. **Why Adrenalectomy is Correct:** When bilateral adrenalectomy is performed (historically used to treat refractory Cushing’s disease), the source of endogenous cortisol is removed. This results in the loss of the negative feedback mechanism on the hypothalamus and pituitary gland. In the absence of cortisol, the pituitary corticotrophs undergo rapid hyperplasia and hypertrophy, leading to the formation of a large, aggressive **ACTH-secreting pituitary macroadenoma**. This results in extremely high levels of ACTH and hyperpigmentation. **Why Other Options are Incorrect:** * **Hypopituitarism:** This involves a deficiency of pituitary hormones; Nelson syndrome is characterized by the *excessive* production of ACTH. * **Deficiency of Beta Cells:** This refers to Type 1 Diabetes Mellitus (insulin deficiency) and has no physiological link to the pituitary-adrenal axis. * **Deficiency of Growth Hormone:** This leads to short stature/dwarfism. Nelson syndrome specifically involves the corticotroph (ACTH) lineage, not somatotrophs. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** History of bilateral adrenalectomy, hyperpigmentation (due to high ACTH/MSH), and an enlarging pituitary mass (causing bitemporal hemianopia). * **Diagnosis:** Elevated plasma ACTH levels and MRI showing a pituitary adenoma. * **Prevention:** The incidence has decreased significantly due to the use of pituitary surgery (transsphenoidal resection) and radiotherapy instead of bilateral adrenalectomy for Cushing’s disease.

Q: Which of the following findings is consistent with a diagnosis of delayed puberty?

Menarche delayed beyond 16 years of age. ### Explanation **Delayed puberty** is defined by the absence of secondary sexual characteristics by an age that is 2 to 2.5 standard deviations above the mean for the population. #### 1. Why Option B is Correct In girls, delayed puberty is clinically diagnosed if: * There is **no breast development (Thelarche)** by age **13**. * There is a gap of >5 years between thelarche and menarche. * **Menarche** has not occurred by age **16** (regardless of secondary sexual development). Therefore, menarche delayed beyond 16 years is a definitive criterion for delayed puberty. #### 2. Analysis of Incorrect Options * **Option A:** Breast budding (Thelarche) at age 10 is perfectly normal. The normal range for thelarche is 8–13 years. * **Option C:** Menarche typically occurs 2–2.5 years after thelarche (Stage B2). Menarche occurring 1 year after budding is slightly early but does not constitute "delayed" puberty. * **Option D:** FSH levels vary significantly based on the etiology. In **Hypogonadotropic Hypogonadism** (e.g., Kallmann syndrome), FSH is low ( 20 mIU/mL). A value "less than 20" is too non-specific to define delayed puberty. #### 3. High-Yield Clinical Pearls for NEET-PG * **Most Common Cause:** Constitutional Delay of Growth and Puberty (CDGP) is the most common cause in both sexes (characterized by "late bloomers" with delayed bone age). * **Male Criteria:** Delayed puberty in boys is defined as lack of testicular enlargement (**<4 mL or <2.5 cm**) by age **14**. * **Sequence in Girls:** Thelarche $\rightarrow$ Adrenarche/Pubarche $\rightarrow$ Growth Spurt $\rightarrow$ Menarche. * **Sequence in Boys:** Testicular enlargement $\rightarrow$ Penile growth $\rightarrow$ Pubarche $\rightarrow$ Growth Spurt.

Q: What percentage of pheochromocytomas are malignant?

10%. In clinical medicine and endocrinology, pheochromocytoma is famously known as the **"Rule of 10" tumor**. This mnemonic is a high-yield concept for NEET-PG, as it summarizes the epidemiological distribution of these catecholamine-secreting tumors. ### **Why 10% is Correct** Statistically, approximately **10% of pheochromocytomas are malignant**. Unlike many other tumors, malignancy in pheochromocytoma cannot be determined by histological appearance alone (cellular atypia or mitosis). Instead, malignancy is strictly defined by the **presence of distant metastasis** to non-chromaffin tissues, such as the lungs, liver, or bones. ### **Analysis of Incorrect Options** * **A (5%):** This underestimates the malignancy rate. While some pediatric series show variation, 10% remains the standard teaching for general boards. * **C & D (20% & 15%):** These percentages are too high for sporadic pheochromocytomas. However, it is important to note that malignancy rates can be significantly higher (up to 35-50%) in patients with specific genetic mutations, such as **SDHB mutations**. ### **Clinical Pearls for NEET-PG** To master this topic, remember the complete **"Rule of 10s"**: 1. **10% Malignant:** Defined by metastasis. 2. **10% Bilateral:** Often associated with familial syndromes. 3. **10% Extra-adrenal:** These are called **Paragangliomas** (most common site: Organ of Zuckerkandl). 4. **10% Pediatric:** Though rare, they are a classic cause of secondary hypertension in children. 5. **10% Familial:** (Note: Modern genetics suggests this may now be as high as 30-35%, but "10%" remains the classic exam answer). **High-Yield Fact:** The most sensitive screening test is **Plasma free metanephrines**, while the most specific is **24-hour urinary metanephrines**. For localization, **MIBG scan** is used if CT/MRI is inconclusive.

Q: When does the hypothalamopituitary axis become active and functional?

20th week of gestation. **Explanation:** The development of the endocrine system is a critical milestone in fetal physiology. The **hypothalamo-pituitary axis (HPA)** begins its structural development early in the first trimester, but it becomes **functionally integrated and active by the 20th week of gestation.** 1. **Why Option A is correct:** By the 20th week, the portal vascular system connecting the hypothalamus and the anterior pituitary is fully developed. This allows hypothalamic releasing hormones (like TRH, CRH, and GnRH) to trigger the secretion of pituitary hormones (TSH, ACTH, LH/FSH) into the fetal circulation. At this stage, feedback loops also begin to function, allowing the fetus to regulate its own hormonal environment independent of the mother. 2. **Why Options B, C, and D are incorrect:** These options suggest postnatal activation. While the HPA axis undergoes a "surge" after birth (e.g., the TSH surge or "mini-puberty" of infancy), the system is already fully operational in utero to support fetal growth and organ maturation. Waiting until the 5th week or 5th year of life would be incompatible with normal fetal development and metabolic homeostasis. **High-Yield Clinical Pearls for NEET-PG:** * **Rathke’s Pouch:** The anterior pituitary (adenohypophysis) is derived from oral ectoderm (Rathke’s pouch), while the posterior pituitary (neurohypophysis) is derived from neural ectoderm. * **Growth Hormone (GH):** Fetal growth is largely independent of fetal GH; it is primarily driven by **Insulin-like Growth Factors (IGF-1 and IGF-2)** and insulin. * **Thyroid:** The fetal thyroid starts trapping iodine by the **10th–12th week**, but full HPA regulation occurs by the 20th week. * **Cortisol:** Fetal ACTH stimulates the adrenal cortex, which is crucial for lung surfactant production near term.

Q: Advanced bone age is seen in all except?

Marfan's syndrome. **Explanation:** Bone age is a measure of skeletal maturity and is typically determined by an X-ray of the left hand and wrist. **Advanced bone age** occurs when skeletal maturation is faster than chronological age, usually due to the premature or excessive influence of sex steroids or growth-promoting hormones. **1. Why Marfan’s Syndrome is the Correct Answer:** In **Marfan’s syndrome**, patients exhibit tall stature and arachnodactyly, but their **bone age is typically normal** (concordant with chronological age). The increased height is due to connective tissue abnormalities and long bone overgrowth, not hormonal acceleration of epiphyseal closure. Therefore, it does not cause advanced bone age. **2. Analysis of Incorrect Options:** * **Congenital Adrenal Hyperplasia (CAH):** Excess adrenal androgens (e.g., in 21-hydroxylase deficiency) lead to rapid skeletal maturation. While these children are initially tall, their epiphyses fuse early, resulting in short adult stature. * **Precocious Puberty:** Early exposure to estrogen or testosterone causes a growth spurt and rapid advancement of bone age, leading to premature epiphyseal fusion. * **Obesity:** Nutritional thyrotoxicosis and increased aromatization of androgens to estrogens in adipose tissue often lead to accelerated linear growth and mildly advanced bone age in prepubertal children. **Clinical Pearls for NEET-PG:** * **Delayed Bone Age:** Seen in Constitutional Delay of Growth and Puberty (CDGP), Hypothyroidism (most significant delay), Growth Hormone deficiency, and Malnutrition. * **Advanced Bone Age:** Seen in CAH, Precocious puberty, Hyperthyroidism, and McCune-Albright Syndrome. * **Key Rule:** If Bone Age = Chronological Age < Height Age, think of **Genetic Tall Stature** or **Marfan’s**.

Question 1

Which genetic syndrome is characterized by obesity and mental retardation?

Accepted Answer

Prader-Willi syndrome

Answer

Turner syndrome

Answer

Fragile-X syndrome

Answer

Noonan syndrome

Question 2

A 8-year-old child presents with lethargy, multiple epiphyseal breaks, wormian bones, and growth and mental retardation. What is the diagnosis?

Accepted Answer

Hypothyroidism

Answer

Rickets

Answer

Scurvy

Answer

Hypoparathyroidism

Question 3

Which of the following is NOT a metabolic abnormality seen in congenital adrenal hyperplasia?

Accepted Answer

Hypokalemia

Answer

Hypotension

Answer

Hyponatremia

Answer

Metabolic acidosis

Question 4

What is the most common central nervous system tumor associated with precocious puberty?

Accepted Answer

Hamartoma

Answer

Astrocytoma

Answer

Neurofibroma

Answer

Ependymoma

Question 5

Turner syndrome - karyotyping is:

Accepted Answer

45, XO

Answer

46XO

Answer

47 XXX

Answer

Trisomy 21

Question 6

Nelson syndrome is seen in which of the following conditions?

Accepted Answer

Adrenalectomy

Answer

Hypopituitarism

Answer

Deficiency of beta cells

Answer

Deficiency of growth hormone

Question 7

Which of the following findings is consistent with a diagnosis of delayed puberty?

Accepted Answer

Menarche delayed beyond 16 years of age

Answer

Breast budding in a 10-year-old girl

Answer

Menarche occurring 1 year after breast budding

Answer

FSH values less than 20 mIU/mL

Question 8

What percentage of pheochromocytomas are malignant?

Accepted Answer

10%

Answer

5%

Answer

20%

Answer

15%

Question 9

When does the hypothalamopituitary axis become active and functional?

Accepted Answer

20th week of gestation

Answer

5th year of life

Answer

5th week of life

Answer

5th month of life

Question 10

Advanced bone age is seen in all except?

Accepted Answer

Marfan's syndrome

Answer

Congenital adrenal hyperplasia

Answer

Precocious puberty

Answer

Obesity

Endocrinology — MCQs

Endocrinology — MCQs

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