Endocrinology Practice Questions

Q: Salt losing hydroxylase deficiency is characterized by?

Hyponatremia. **Explanation:** Salt-losing hydroxylase deficiency most commonly refers to **21-hydroxylase deficiency**, the most frequent cause of **Congenital Adrenal Hyperplasia (CAH)**. **1. Why Hyponatremia is the Correct Answer:** In this condition, a deficiency of the enzyme 21-hydroxylase leads to a failure in the synthesis of **Aldosterone** and **Cortisol**. Aldosterone is responsible for sodium reabsorption and potassium excretion in the distal renal tubules. Its absence results in "salt wasting"—the excessive loss of sodium in the urine—leading to profound **Hyponatremia**. This is the hallmark biochemical finding in the salt-wasting form of CAH. **2. Analysis of Other Options:** * **Hyperkalemia (Option B):** While hyperkalemia *is* a classic feature of salt-losing CAH (due to lack of aldosterone-mediated potassium excretion), the question asks for the primary characterization of "salt losing." In medical entrance exams, when both are present, hyponatremia is often prioritized as the defining "salt-losing" event, though both are clinically significant. * **Hypoglycemia (Option C):** Deficiency of Cortisol (a counter-regulatory hormone) can lead to hypoglycemia, especially during stress. However, it is a secondary metabolic consequence rather than the defining feature of the "salt-losing" state. * **Hypocalcemia (Option D):** Calcium metabolism is generally unaffected in CAH; this is not a feature of hydroxylase deficiencies. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Enzyme:** 21-hydroxylase deficiency (>90% of cases). * **Biochemical Marker:** Elevated **17-hydroxyprogesterone (17-OHP)**. * **Clinical Presentation:** Ambiguous genitalia in females (virilization) and salt-wasting crisis (vomiting, dehydration, shock) in the second week of life. * **11-beta-hydroxylase deficiency:** Characterized by **hypertension** (due to 11-deoxycorticosterone buildup) rather than salt-wasting.

Q: True about Laron dwarfism is:

Growth hormone insensitivity. **Explanation:** **Laron Syndrome (Laron Dwarfism)** is an autosomal recessive condition characterized by severe short stature due to **Growth Hormone (GH) insensitivity**. 1. **Why Option B is Correct:** The primary defect in Laron syndrome is a mutation in the **Growth Hormone Receptor (GHR)** gene. Although the pituitary gland secretes GH normally (or even in excess), the peripheral tissues cannot respond to it. This failure of GH to bind to its receptor leads to a failure in the production of **Insulin-like Growth Factor-1 (IGF-1)**, which is the mediator of GH's growth-promoting effects. 2. **Why Other Options are Incorrect:** * **Option A:** GH levels are typically **elevated or normal**, not deficient. The body attempts to compensate for the perceived lack of GH action by secreting more. * **Option C:** Plasma **IGF-1 is markedly decreased**, not increased. Since the GH receptor is defective, the liver cannot synthesize IGF-1. * **Option D:** Plasma **IGF-BP3 (and GHBP) levels are low**. IGF-BP3 is GH-dependent; without functional GH signaling, its levels fall significantly. **High-Yield Clinical Pearls for NEET-PG:** * **Phenotype:** Patients present with "doll-like" facies, prominent forehead, small chin, high-pitched voice, and truncal obesity. * **Biochemical Hallmark:** High GH + Low IGF-1. * **Metabolic Feature:** Recurrent **fasting hypoglycemia** (due to the lack of the counter-regulatory effects of IGF-1/GH). * **Treatment:** Recombinant human **IGF-1 (Mecasermin)**. Exogenous GH is ineffective because the receptors are non-functional. * **Unique Fact:** Interestingly, individuals with Laron syndrome show a striking **resistance to cancer and Type 2 diabetes**.

Q: Congenital adrenal hyperplasia is most likely a result of which of the following?

Defects in adrenal steroidogenic enzymes. **Explanation:** **Congenital Adrenal Hyperplasia (CAH)** is a group of autosomal recessive disorders characterized by a deficiency in one of the enzymes required for the synthesis of cortisol from cholesterol in the adrenal cortex. **1. Why Option A is Correct:** The primary pathology in CAH is a **defect in adrenal steroidogenic enzymes**. The most common deficiency (95% of cases) is **21-hydroxylase**. When cortisol synthesis is impaired, the lack of negative feedback leads to an overproduction of **Adrenocorticotropic Hormone (ACTH)** by the pituitary. Chronic ACTH stimulation causes **hyperplasia** of the adrenal cortex and shunts precursor steroids into the androgen pathway, leading to virilization. **2. Why Other Options are Incorrect:** * **Option B (Addison’s Disease):** This is primary adrenal insufficiency, usually due to autoimmune destruction or infection (TB). While it involves low cortisol, it is an acquired destruction of the gland, not a congenital enzymatic defect. * **Option C (Defects in ACTH secretion):** CAH actually features *increased* ACTH secretion. A defect/deficiency in ACTH would lead to secondary adrenal insufficiency and adrenal *atrophy*, not hyperplasia. * **Option D (Defects in CBG):** Corticosteroid-binding globulin (Transcortin) carries cortisol in the blood. Defects here affect total cortisol levels but do not cause the enzymatic block or androgen excess seen in CAH. **High-Yield Clinical Pearls for NEET-PG:** * **Most common enzyme deficiency:** 21-hydroxylase (leads to high 17-OH Progesterone). * **Classic Presentation:** Ambiguous genitalia in females, salt-wasting crisis (hyponatremia, hyperkalemia, hypotension) in males. * **11β-hydroxylase deficiency:** Differentiated by the presence of **hypertension** (due to 11-deoxycorticosterone buildup). * **Treatment:** Glucocorticoid replacement (to suppress ACTH) and mineralocorticoids if salt-wasting.

Q: What is the recommended screening time for neonatal hypothyroidism after birth?

2-4 days after birth. **Explanation:** The primary goal of screening for Congenital Hypothyroidism (CH) is to detect the condition early to prevent irreversible intellectual disability. **Why 2-4 days (48-96 hours) is the correct timing:** Immediately after birth, there is a physiological **"TSH surge"** caused by the cold stress of delivery. TSH levels peak within 30–60 minutes of birth and remain high for the first 24–48 hours. If screening is performed during this window, it leads to a high rate of **false-positive** results. Waiting until 48–96 hours allows TSH levels to stabilize, ensuring that an elevated TSH is truly indicative of hypothyroidism rather than a transient neonatal surge. **Analysis of Incorrect Options:** * **Options C & D (1-4 hours):** These are incorrect because they coincide with the peak of the physiological TSH surge, leading to inaccurate results. * **Option A (1-2 days):** While some programs screen after 24 hours to facilitate early discharge, the risk of false positives remains higher than the 2-4 day window. **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause:** Thyroid dysgenesis (Ectopy is the most common specific type). * **Clinical Presentation:** Most neonates are **asymptomatic** at birth due to maternal T4 crossing the placenta. Early signs include a large posterior fontanelle, prolonged jaundice, hoarse cry, and umbilical hernia. * **Treatment Goal:** Start Levothyroxine (10-15 μg/kg/day) within the first **2 weeks** of life to ensure normal neurodevelopment. * **Sample Collection:** Capillary blood via **heel prick** onto a Guthrie card (filter paper).

Q: Mental retardation is not typically seen in which of the following conditions?

Hypopituitarism. **Explanation:** The core concept tested here is the role of specific hormones and insults in neurodevelopment. **Hypopituitarism** (Option C) typically involves deficiencies in Growth Hormone (GH), ACTH, TSH, and Gonadotropins. While GH is essential for linear growth and metabolic functions, it is **not required for brain development** or cognitive function. Children with isolated GH deficiency or panhypopituitarism usually have normal intelligence, though they may experience delayed physical milestones and "doll-like" facial features. **Why the other options are incorrect:** * **Down Syndrome (Option A):** This is the most common chromosomal cause of intellectual disability (mental retardation). It is characterized by varying degrees of cognitive impairment due to trisomy 21. * **Cretinism (Option B):** Congenital hypothyroidism is a leading cause of *preventable* mental retardation. Thyroid hormones (T3/T4) are critical for neuronal migration, myelination, and synaptic connectivity during the first two years of life. * **Birth Asphyxia (Option D):** Hypoxic-Ischemic Encephalopathy (HIE) resulting from birth asphyxia leads to permanent neuronal damage. It is a major cause of cerebral palsy and associated intellectual disability. **High-Yield Clinical Pearls for NEET-PG:** 1. **GH vs. Thyroid:** GH deficiency causes "Short Stature with Normal IQ"; Thyroid deficiency causes "Short Stature with Low IQ." 2. **Laron Syndrome:** A type of GH insensitivity characterized by very short stature but normal intelligence. 3. **Bone Age:** In both Hypothyroidism and Hypopituitarism, bone age is significantly delayed compared to chronological age. 4. **Micropenis:** In a neonate, the triad of hypoglycemia, jaundice, and micropenis strongly suggests Congenital Hypopituitarism.

Q: A child presents with hypercalcemia and hyperphosphatemia. What is the most likely diagnosis?

Renal osteodystrophy. **Explanation:** The hallmark of **Renal Osteodystrophy** (specifically in the context of Chronic Kidney Disease-Mineral and Bone Disorder) is the inability of the kidneys to excrete phosphate, leading to **hyperphosphatemia**. While early stages often show hypocalcemia, the development of **Tertiary Hyperparathyroidism** (autonomous PTH secretion) or the administration of calcium-based phosphate binders and Vitamin D analogs often results in **hypercalcemia**. The combination of high calcium and high phosphate is a classic laboratory finding in advanced renal bone disease. **Why the other options are incorrect:** * **Vitamin D Dependent Rickets (VDDR):** Caused by a defect in 1-alpha-hydroxylase (Type I) or Vitamin D receptors (Type II). Both types present with **hypocalcemia** and **hypophosphatemia** (due to secondary hyperparathyroidism). * **Vitamin D Resistant Rickets (X-linked Hypophosphatemic Rickets):** Characterized by renal phosphate wasting. It presents with **hypophosphatemia** and usually normal serum calcium levels. * **Hypophosphatasia:** A genetic deficiency of alkaline phosphatase. While it can cause hypercalcemia and hyperphosphatemia, it is characterized by a pathognomonic **very low Serum Alkaline Phosphatase (ALP)** level, which distinguishes it from other metabolic bone diseases. **NEET-PG High-Yield Pearls:** * **Calcium-Phosphate Product:** In Renal Osteodystrophy, if $Ca \times PO_4 > 55 \text{ mg}^2/\text{dL}^2$, there is a high risk of metastatic calcification (calciphylaxis). * **Rickets vs. Renal Osteodystrophy:** Most forms of Rickets present with *low* phosphate; Renal Osteodystrophy is the major pediatric bone pathology presenting with *high* phosphate. * **Radiology:** Look for "Rugger-jersey spine" (subperiosteal resorption) in renal osteodystrophy.

Q: What is the most common cause of peripheral precocious puberty in males?

Congenital adrenal hyperplasia. **Explanation:** Precocious puberty is defined as the onset of secondary sexual characteristics before age 9 in boys. It is divided into **Central (GnRH-dependent)** and **Peripheral (GnRH-independent)** types. **1. Why Congenital Adrenal Hyperplasia (CAH) is correct:** In males, peripheral precocious puberty is characterized by virilization (pubic hair, phallic enlargement) without a corresponding increase in testicular volume (testes remain prepubertal, <4ml). **Congenital Adrenal Hyperplasia (specifically 21-hydroxylase deficiency)** is the most common cause. It leads to an overproduction of adrenal androgens, which bypasses the Hypothalamic-Pituitary-Gonadal (HPG) axis, causing "isosexual" precocity. **2. Analysis of Incorrect Options:** * **Constitutional (Option B):** This refers to "Constitutional Delay," which is a variation of normal growth leading to *late* puberty, not precocious puberty. * **Klinefelter's syndrome (Option C):** This is a chromosomal anomaly (47, XXY) typically associated with *delayed* puberty and hypergonadotropic hypogonadism, not precocity. * **CNS Pathology (Option D):** CNS lesions (e.g., hypothalamic hamartomas) are the most common cause of **Central** (True) precocious puberty in males, where the HPG axis is activated early, leading to increased testicular volume. **High-Yield Clinical Pearls for NEET-PG:** * **Testicular Volume Rule:** In precocious puberty, if testes are **enlarged** (>4ml), think **Central** causes. If testes are **small/prepubertal**, think **Peripheral** (Adrenal) causes. * **Exception:** In CAH, if ectopic adrenal rests are present in the testes, they may appear enlarged, but this is rare. * **McCune-Albright Syndrome:** A classic cause of peripheral precocity in girls (triad of café-au-lait spots, polyostotic fibrous dysplasia, and autonomous endocrine function).

Q: Which endocrine disorder is associated with epiphyseal dysgenesis?

Hypothyroidism. **Explanation:** **Hypothyroidism** is the correct answer because thyroid hormones are essential for normal linear growth and skeletal maturation. In congenital or juvenile hypothyroidism, there is a significant delay in the appearance of ossification centers. When these centers finally appear, they do so from multiple small foci rather than a single center. These foci fail to coalesce normally, resulting in a fragmented, stippled, or "moth-eaten" appearance on X-ray, known as **epiphyseal dysgenesis**. This is most commonly seen in the femoral head and is a hallmark radiological sign of the condition. **Why other options are incorrect:** * **Cushing’s Syndrome:** Excess glucocorticoids lead to growth failure and osteoporosis (decreased bone density), but they do not cause the specific fragmented pattern of dysgenesis seen in hypothyroidism. * **Addison’s Disease:** Chronic adrenocortical insufficiency primarily affects electrolyte balance and blood pressure; it does not typically manifest with specific epiphyseal maturation defects. * **Hypoparathyroidism:** This condition leads to hypocalcemia and hyperphosphatemia. While it may cause basal ganglia calcification or dental enamel hypoplasia, it is not associated with epiphyseal dysgenesis. **High-Yield Clinical Pearls for NEET-PG:** * **Bone Age:** In hypothyroidism, bone age is significantly delayed compared to chronological age. * **Most Common Cause:** Worldwide, iodine deficiency is the most common cause of congenital hypothyroidism; in iodine-sufficient areas, it is thyroid dysgenesis. * **Other Skeletal Findings:** Look for a "double-contoured" appearance of vertebrae or a "bullet-shaped" vertebra (T12/L1) in hypothyroid patients. * **Screening:** The best time to screen for congenital hypothyroidism is between 48–72 hours of life to avoid the physiological TSH surge.

Question 1

Salt losing hydroxylase deficiency is characterized by?

Accepted Answer

Hyponatremia

Answer

Hyperkalemia

Answer

Hypoglycemia

Answer

Hypocalcemia

Question 2

True about Laron dwarfism is:

Accepted Answer

Growth hormone insensitivity

Answer

Growth hormone deficiency

Answer

Plasma IGF-1 is markedly increased

Answer

Plasma IGF-BP3 at normal levels

Question 3

Congenital adrenal hyperplasia is most likely a result of which of the following?

Accepted Answer

Defects in adrenal steroidogenic enzymes

Answer

Addison's disease

Answer

Defects in ACTH secretion

Answer

Defects in corticosteroid-binding globulin

Question 4

What is the recommended screening time for neonatal hypothyroidism after birth?

Accepted Answer

2-4 days after birth

Answer

1-2 days after birth

Answer

1-2 hours after birth

Answer

2-4 hours after birth

Question 5

A newborn with ambiguous genitalia and a 46,XY karyotype develops vomiting, low serum sodium concentration, and high serum potassium. Which of the following enzymes is most likely to be abnormal?

Accepted Answer

21-hydroxylase

Answer

An enzyme involved in ovarian development

Answer

5a-reductase

Answer

An androgen receptor

Question 6

Mental retardation is not typically seen in which of the following conditions?

Accepted Answer

Hypopituitarism

Answer

Down syndrome

Answer

Cretinism

Answer

Birth asphyxia

Question 7

A child presents with hypercalcemia and hyperphosphatemia. What is the most likely diagnosis?

Accepted Answer

Renal osteodystrophy

Answer

Vitamin D dependent rickets

Answer

Vitamin D resistant rickets

Answer

Hypophosphatasia

Question 8

What is the most common cause of peripheral precocious puberty in males?

Accepted Answer

Congenital adrenal hyperplasia

Answer

Constitutional

Answer

Klinefelter's syndrome

Answer

CNS pathology

Question 9

Pseudohermaphroditism in a female child is most commonly due to which of the following enzymatic deficiencies?

Accepted Answer

21-hydroxylase deficiency

Answer

17-hydroxylase deficiency

Answer

11-hydroxylase deficiency

Answer

3-hydroxylase deficiency

Question 10

Which endocrine disorder is associated with epiphyseal dysgenesis?

Accepted Answer

Hypothyroidism

Answer

Cushing's syndrome

Answer

Addison's disease

Answer

Hypoparathyroidism

Endocrinology — MCQs

Endocrinology — MCQs

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