Endocrinology Practice Questions

Q: Which of the following changes occur in bone growth?

Increased osteocalcin. ### Explanation **Correct Answer: D. Increased osteocalcin** **Why it is correct:** Bone growth and remodeling are driven by the activity of **osteoblasts** (bone-forming cells). **Osteocalcin** (also known as Bone Gamma-Carboxyglutamic Acid Protein) is a non-collagenous protein hormone synthesized exclusively by osteoblasts. It plays a crucial role in bone mineralization and calcium ion binding. Because its synthesis is specific to osteoblasts, serum levels of osteocalcin are considered a highly specific **biochemical marker of bone formation** and turnover. During periods of active bone growth, osteoblast activity increases, leading to elevated osteocalcin levels. **Why the other options are incorrect:** * **A. Increased acid phosphatase:** Tartrate-resistant acid phosphatase (TRAP) is a marker of **osteoclast** activity (bone resorption), not bone growth. * **B. Increased urinary calcium:** High urinary calcium (hypercalciuria) is typically a sign of bone resorption or impaired renal reabsorption, often seen in conditions like hyperparathyroidism or immobilization, rather than healthy bone growth. * **C. Increased bone nucleotidase:** While 5'-nucleotidase is a marker for liver/biliary disease, it is not a specific or standard marker for bone growth or mineralization. **NEET-PG High-Yield Pearls:** * **Markers of Bone Formation:** Osteocalcin, Bone-specific Alkaline Phosphatase (ALP), and Procollagen type 1 N-terminal propeptide (P1NP). * **Markers of Bone Resorption:** Urinary hydroxyproline, Pyridinoline cross-links, and Serum TRAP. * **Vitamin K Dependency:** Osteocalcin requires Vitamin K for carboxylation to become functional; thus, Vitamin K deficiency can impair bone mineralization. * **Metabolic Link:** Osteocalcin also acts as a hormone that increases insulin secretion and sensitivity, linking bone metabolism to energy homeostasis.

Q: Which of the following hormones is not involved in the regulation of food intake?

Gastrin. The regulation of food intake is governed by the **hypothalamus**, which integrates signals from peripheral hormones to balance hunger (orexigenic) and satiety (anorexigenic) signals. **Why Gastrin is the Correct Answer:** **Gastrin** is a gastrointestinal hormone primarily responsible for stimulating **gastric acid (HCl) secretion** from parietal cells and promoting the growth of the gastric mucosa. While it is vital for digestion, it does not play a direct role in the hypothalamic regulation of appetite or long-term energy balance. **Analysis of Incorrect Options:** * **Ghrelin:** Known as the "hunger hormone," it is secreted by P/D1 cells of the stomach fundus. It is the only major peripheral **orexigenic** hormone; it stimulates the NPY/AgRP neurons in the arcuate nucleus to increase food intake. * **Insulin:** Secreted by the pancreas in response to high blood glucose, insulin acts as a **satiety signal**. It crosses the blood-brain barrier to inhibit food intake and regulate long-term energy homeostasis. * **Leptin:** Produced by adipose tissue (the "satiety hormone"), it signals the brain about the body's fat stores. It stimulates POMC/CART neurons and inhibits NPY/AgRP neurons, thereby **decreasing food intake**. **High-Yield Clinical Pearls for NEET-PG:** * **Arcuate Nucleus:** The "master center" for appetite regulation in the hypothalamus. * **Prader-Willi Syndrome:** Characterized by hyperphagia and obesity due to extremely high levels of **Ghrelin**. * **Cholecystokinin (CCK):** Another important GI hormone that acts as a short-term satiety signal (unlike Gastrin). * **Leptin Resistance:** The primary mechanism behind obesity, where the brain fails to respond to high levels of circulating leptin.

Q: What is the primary function of Follistatin?

Prevents interaction of activin with receptor. **Explanation:** **Follistatin** is a glycoprotein primarily produced by the folliculostellate cells of the anterior pituitary and granulosa cells of the ovary. Its primary physiological role is to act as an **activin-binding protein**. 1. **Why Option C is Correct:** Follistatin functions as an activin antagonist. It binds directly to activin with high affinity, effectively "sequestering" it. This prevents activin from binding to its specific serine/threonine kinase receptors on the cell surface. Since activin is a potent stimulator of FSH synthesis, follistatin’s neutralization of activin leads to a significant reduction in FSH secretion. 2. **Why Other Options are Incorrect:** * **Option A & B:** While follistatin ultimately leads to decreased FSH, its *primary* biochemical mechanism is not a direct modulation of the gonadotrope cell's overall function, but rather the specific inhibition of the activin signaling pathway. * **Option D:** Activin stimulates FSH beta gene expression. Because follistatin inhibits activin, it **suppresses** (rather than stimulates) FSH beta gene expression. **High-Yield NEET-PG Pearls:** * **The TGF-β Superfamily:** Activin, Inhibin, and Follistatin are all part of this family and regulate the HPO axis. * **Activin vs. Inhibin:** Activin *increases* FSH; Inhibin *decreases* FSH. * **Follistatin’s Dual Role:** Beyond the pituitary, follistatin plays a role in muscle growth by binding to and inhibiting **Myostatin** (a negative regulator of muscle mass). * **Clinical Correlation:** Elevated follistatin levels are often observed in Polycystic Ovary Syndrome (PCOS), contributing to the characteristic arrest of follicular development.

Q: A person sustains head trauma leading to a transaction of the pituitary stalk. All can be a consequence of this, except?

Diabetes mellitus. **Explanation:** Pituitary stalk transection (disruption of the infundibulum) disconnects the hypothalamus from the pituitary gland, leading to significant endocrine disturbances. **Why Diabetes Mellitus is the correct answer:** Diabetes Mellitus is a disorder of insulin deficiency or resistance related to the pancreas. Pituitary stalk injury actually leads to a **deficiency of Growth Hormone (GH) and ACTH (Cortisol)**. Since GH and Cortisol are "diabetogenic" (counter-regulatory) hormones that increase blood glucose, their absence increases insulin sensitivity and can lead to **hypoglycemia**, not Diabetes Mellitus. **Analysis of other options:** * **Diabetes Insipidus (DI):** The posterior pituitary stores ADH produced in the hypothalamus. Stalk transection halts the transport of ADH, leading to Central DI (polyuria and polydipsia). * **Hyperprolactinemia:** Prolactin is the only pituitary hormone under tonic **inhibition** by hypothalamic Dopamine (Prolactin Inhibiting Factor). Disruption of the stalk prevents dopamine from reaching the anterior pituitary, causing "disinhibition" and a rise in prolactin levels. * **SIADH:** While DI is more common, head trauma or the "triphasic response" following stalk injury can cause a transient, inappropriate release of stored ADH from the degenerating posterior pituitary terminals, leading to SIADH. **High-Yield Clinical Pearls for NEET-PG:** * **The Triphasic Response in Stalk Injury:** 1. Initial DI (axonal shock), 2. Transient SIADH (leakage of stored ADH), 3. Permanent DI (death of neurons). * **The "Stalk Effect":** Any lesion compressing the stalk (e.g., Craniopharyngioma) causes hyperprolactinemia, but levels are usually <200 ng/mL (unlike Prolactinomas). * **Panhypopituitarism:** Stalk transection leads to a deficiency of all anterior pituitary hormones *except* Prolactin.

Q: All of the following are glycoproteins, EXCEPT:

GH. **Explanation:** The hormones of the anterior pituitary are chemically classified into three main groups: Glycoproteins, Pro-opiomelanocortin (POMC) derivatives, and Somatotropic hormones (Polypeptides). **1. Why GH is the correct answer:** **Growth Hormone (GH)** and **Prolactin (PRL)** belong to the Somatotropic hormone family. They are single-chain **polypeptides** (GH has 191 amino acids), not glycoproteins. They do not contain carbohydrate moieties and share structural similarities with human placental lactogen (hPL). **2. Why the other options are incorrect:** Options A, B, and C (**TSH, FSH, and LH**) along with the placental hormone **hCG**, form the **Glycoprotein family**. * These hormones are composed of two subunits: **Alpha (α) and Beta (β)**. * The **α-subunit is identical** in all four hormones. * The **β-subunit is unique** and confers biological and immunological specificity to each hormone. **High-Yield Clinical Pearls for NEET-PG:** * **Common α-subunit:** Because TSH, FSH, LH, and hCG share the same α-subunit, extremely high levels of hCG (as seen in Hydatidiform mole) can cross-react with TSH receptors, leading to hyperthyroidism. * **Acidophils vs. Basophils:** * **Acidophils** secrete GH and Prolactin (Mnemonic: **GPA** - **G**rowth hormone, **P**rolactin are **A**cidophils). * **Basophils** secrete the glycoproteins TSH, FSH, and LH (Mnemonic: **B-FLAT** - **B**asophils: **F**SH, **L**H, **A**CTH, **T**SH). * **Smallest Pituitary Hormone:** Vasopressin/ADH (9 amino acids). * **Largest Pituitary Hormone:** GH (191 amino acids).

Q: All of the following hormones accelerate the release of free fatty acids (FFA) from adipose tissue, EXCEPT:

Insulin. **Explanation:** The mobilization of free fatty acids (FFA) from adipose tissue is primarily regulated by the enzyme **Hormone-Sensitive Lipase (HSL)**. This enzyme catalyzes the breakdown of stored triglycerides into glycerol and FFAs (lipolysis). **1. Why Insulin is the Correct Answer:** Insulin is the most potent **anti-lipolytic** hormone. It inhibits HSL through the activation of phosphodiesterase, which lowers intracellular cAMP levels. Furthermore, insulin promotes glucose uptake into adipocytes (via GLUT-4) and stimulates **alpha-glycerophosphate** production, which favors the re-esterification of FFAs back into triglycerides. Therefore, insulin decreases the release of FFA into the plasma. **2. Why the Other Options are Incorrect:** * **Epinephrine & Norepinephrine (Catecholamines):** These are potent stimulators of lipolysis. They bind to **$\beta_3$-adrenergic receptors** on adipocytes, increasing cAMP levels, which activates Protein Kinase A (PKA). PKA then phosphorylates and activates HSL, accelerating FFA release. * **Vasopressin (ADH):** While its primary role is water reabsorption, at higher concentrations, vasopressin exerts a "pressor" effect and has been shown to stimulate lipolysis in adipose tissue via V1a receptors. **Clinical Pearls for NEET-PG:** * **Lipolytic Hormones (The "Stress" Hormones):** Glucagon, Epinephrine, Norepinephrine, Cortisol, Growth Hormone, and ACTH all increase FFA release. * **Rate-Limiting Enzyme:** Hormone-Sensitive Lipase (HSL) is the rate-limiting step for lipolysis. * **Insulin's Dual Action:** It inhibits HSL (preventing breakdown) and stimulates **Lipoprotein Lipase (LPL)** in capillary walls (promoting storage). * **Ketogenesis Connection:** In states of absolute insulin deficiency (like DKA), unchecked HSL activity leads to a massive influx of FFAs to the liver, providing the substrate for ketone body synthesis.

Q: Orexins play an important role in eating disorders. All of the following are orexins, EXCEPT?

Leptin. **Explanation:** The regulation of appetite is controlled by the hypothalamus through two types of signals: **Orexigenic** (appetite-stimulating) and **Anorexigenic** (appetite-suppressing). **Why Leptin is the correct answer:** Leptin is an **anorexigenic** hormone produced by adipocytes (fat cells). It acts on the arcuate nucleus of the hypothalamus to inhibit hunger and stimulate satiety. Therefore, it is not an orexin; rather, it is an "anti-orexin" or satiety factor. **Analysis of incorrect options:** * **Orexin-A and Orexin-B:** These are neuropeptides produced in the lateral hypothalamus (the "feeding center"). They strongly stimulate food intake and play a vital role in regulating wakefulness. * **Hypocretin 1 and 2:** These are alternative names for Orexin-A and Orexin-B, respectively. The terms are used interchangeably in medical literature (Hypocretin-1 = Orexin-A; Hypocretin-2 = Orexin-B). Since they promote feeding, they are true orexins. **High-Yield Clinical Pearls for NEET-PG:** * **Narcolepsy Connection:** A deficiency of orexin (hypocretin) producing neurons in the hypothalamus is the primary cause of **Narcolepsy Type 1** (associated with cataplexy). * **The "Satiety Center":** The **Ventromedial Nucleus (VMN)** of the hypothalamus is the satiety center (lesion leads to obesity). * **The "Feeding Center":** The **Lateral Hypothalamus (LHA)** is the feeding center where orexins are produced (lesion leads to anorexia/starvation). * **Ghrelin:** Known as the "hunger hormone," it is the only peripheral orexigenic hormone (produced by the stomach).

Q: Catecholamine hormones are synthesized in which location?

Chromaffin cells of the adrenal medulla. **Explanation:** **1. Why Option A is Correct:** Catecholamines (Epinephrine, Norepinephrine, and Dopamine) are synthesized in the **Chromaffin cells** of the **adrenal medulla**. These cells are embryologically derived from the **neural crest** and act as modified postganglionic sympathetic neurons. Within these cells, the amino acid Tyrosine is converted into catecholamines through a series of enzymatic steps. The final step (Norepinephrine to Epinephrine) is catalyzed by the enzyme **PNMT** (Phenylethanolamine N-methyltransferase), which is uniquely induced by high concentrations of cortisol draining from the adrenal cortex. **2. Why Other Options are Incorrect:** Options B, C, and D refer to the **Adrenal Cortex**, which is mesodermal in origin and produces **steroid hormones**, not catecholamines. * **Zona Glomerulosa (B):** The outermost layer, responsible for secreting mineralocorticoids (primarily **Aldosterone**). * **Zona Fasciculata (C):** The middle and widest layer, responsible for secreting glucocorticoids (primarily **Cortisol**). * **Zona Reticularis (D):** The innermost layer of the cortex, responsible for secreting adrenal androgens (e.g., **DHEA**). **3. NEET-PG High-Yield Pearls:** * **Rate-limiting enzyme:** Tyrosine hydroxylase is the rate-limiting step in catecholamine synthesis. * **VMAT-2:** This transporter packages catecholamines into granules (inhibited by Reserpine). * **Tumor Correlation:** **Pheochromocytoma** is a tumor of the chromaffin cells, leading to episodic hypertension due to excessive catecholamine release. * **Rule of 10s:** Pheochromocytoma is 10% bilateral, 10% malignant, and 10% extra-adrenal (where they are called Paragangliomas).

Question 1

What is the direct action of parathyroid hormone (PTH)?

Accepted Answer

Controls the rate of formation of 1,25-dihydroxycholecalciferol

Answer

Controls the rate of 25-hydroxycholecalciferol formation

Answer

Controls the rate of calcium transport in the mucosa of the small intestine

Answer

Controls the rate of formation of calcium-binding protein

Question 2

Which of the following changes occur in bone growth?

Accepted Answer

Increased osteocalcin

Answer

Increased acid phosphatase

Answer

Increased urinary calcium

Answer

Increased bone nucleotidase

Question 3

Which of the following hormones is not involved in the regulation of food intake?

Accepted Answer

Gastrin

Answer

Ghrelin

Answer

Insulin

Answer

Leptin

Question 4

What is the primary function of Follistatin?

Accepted Answer

Prevents interaction of activin with receptor

Answer

Decreases gonadotrope function

Answer

Increases gonadotrope function

Answer

Stimulates FSH beta gene expression

Question 5

A person sustains head trauma leading to a transaction of the pituitary stalk. All can be a consequence of this, except?

Accepted Answer

Diabetes mellitus

Answer

SIADH

Answer

Diabetes insipidus

Answer

Hyperprolactinemia

Question 6

All of the following are glycoproteins, EXCEPT:

Accepted Answer

GH

Answer

TSH

Answer

FSH

Answer

LH

Question 7

All of the following hormones accelerate the release of free fatty acids (FFA) from adipose tissue, EXCEPT:

Accepted Answer

Insulin

Answer

Epinephrine

Answer

Norepinephrine

Answer

Vasopressin

Question 8

Orexins play an important role in eating disorders. All of the following are orexins, EXCEPT?

Accepted Answer

Leptin

Answer

Orexin-A

Answer

Hypocretin 1

Answer

Hypocretin 2

Question 9

Catecholamine hormones are synthesized in which location?

Accepted Answer

Chromaffin cells of the adrenal medulla

Answer

Zona glomerulosa of the adrenal cortex

Answer

Zona fasciculata of the adrenal cortex

Answer

Zona reticularis of the adrenal cortex

Question 10

The occurrence of hypothyroidism following administration of supplemental iodine to subjects with endemic iodine deficiency goiter is known as:

Accepted Answer

Wolff-Chaikoff effect

Answer

Jod-Basedow effect

Answer

Rafetoff Syndrome

Answer

Pendred Syndrome

Endocrinology — MCQs

Endocrinology — MCQs

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