Endocrinology Practice Questions

Q: Which of the following is NOT an appetite suppressant?

Neuropeptide Y. **Explanation:** The regulation of appetite occurs primarily in the **Arcuate Nucleus (ARC)** of the hypothalamus, which contains two distinct sets of neurons: the **Orexigenic** (appetite-stimulating) and **Anorexigenic** (appetite-suppressing) pathways. **Why Neuropeptide Y (NPY) is the correct answer:** Neuropeptide Y is one of the most potent **orexigenic** peptides known. It is co-released with Agouti-related peptide (AgRP) from the ARC. When activated, NPY stimulates food intake, reduces energy expenditure, and promotes fat storage. Therefore, it is an appetite stimulant, not a suppressant. **Analysis of Incorrect Options (Appetite Suppressants):** * **Melanocyte Stimulating Hormone (α-MSH):** This is an anorexigenic peptide derived from Pro-opiomelanocortin (POMC). It acts on MC3 and MC4 receptors in the hypothalamus to inhibit feeding. * **Corticotropin-Releasing Hormone (CRH):** Produced in the paraventricular nucleus, CRH acts as a potent anorexigenic signal, typically reducing food intake during stress responses. * **Leptin:** Produced by adipocytes, Leptin is the "satiety hormone." It crosses the blood-brain barrier to inhibit NPY/AgRP neurons (stimulants) and excite POMC neurons (suppressants), leading to long-term energy balance. **High-Yield Clinical Pearls for NEET-PG:** * **Vagus Nerve:** The primary neural pathway for short-term satiety signals (like CCK) from the gut to the brain. * **Ghrelin:** The only major peripheral hormone that **stimulates** hunger (produced by P/D1 cells of the stomach). * **POMC Deficiency:** Leads to hyperphagia, early-onset obesity, and red hair (due to lack of MSH). * **Mnemonic for ARC:** **N**PY/AgRP = **N**o (stop) fasting/Start eating; **P**OMC/CART = **P**ause eating.

Q: Calcitonin levels are increased in which of the following conditions?

Hyperparathyroidism. **Explanation:** **Correct Option: B. Hyperparathyroidism** The primary stimulus for the secretion of **Calcitonin** (produced by the parafollicular C-cells of the thyroid gland) is **Hypercalcemia**. In Hyperparathyroidism, there is an excess of Parathyroid Hormone (PTH), which leads to elevated serum calcium levels through increased bone resorption and renal calcium reabsorption. As a physiological feedback mechanism, the body increases Calcitonin levels to counteract this hypercalcemia by inhibiting osteoclast activity and promoting renal calcium excretion. **Analysis of Incorrect Options:** * **A. Hyperthyroidism:** This involves excess T3/T4 from follicular cells. While severe thyrotoxicosis can occasionally cause mild hypercalcemia due to increased bone turnover, it is not a primary or classic cause for elevated Calcitonin. * **C. Hypoparathyroidism:** This condition results in **Hypocalcemia**. Low serum calcium levels inhibit the secretion of Calcitonin. * **D. Cushing Syndrome:** Excess glucocorticoids generally lead to decreased bone formation and can cause secondary hyperparathyroidism due to decreased intestinal calcium absorption, but they do not directly stimulate Calcitonin secretion. **High-Yield Clinical Pearls for NEET-PG:** * **Tumor Marker:** Calcitonin is the most sensitive tumor marker for **Medullary Carcinoma of the Thyroid (MCT)**. * **Antagonist:** Calcitonin acts as a physiological antagonist to PTH, but its role in human calcium homeostasis is much weaker than PTH. * **Therapeutic Use:** Exogenous Calcitonin (Salmon calcitonin) is used clinically to treat **Paget’s disease** and severe hypercalcemia. * **Stimuli:** Besides hypercalcemia, GI hormones like **Gastrin** are potent stimulators of Calcitonin secretion.

Q: Pulsatile release of GnRH is important for?

Gonadotrophin stimulation. **Explanation:** The secretion of **Gonadotropin-Releasing Hormone (GnRH)** from the hypothalamus is inherently **pulsatile**. This intermittent release is physiological and essential for the stimulation of the anterior pituitary to secrete LH (Luteinizing Hormone) and FSH (Follicle-Stimulating Hormone). **1. Why Option A is Correct:** The pituitary GnRH receptors require a "rest period" between pulses to remain sensitive. Pulsatile GnRH (occurring every 60–90 minutes) prevents the internalization of receptors, thereby maintaining the synthesis and release of **Gonadotrophins**. **2. Why Other Options are Incorrect:** * **Option B:** While pulsatile GnRH eventually leads to ovulation, its *direct* physiological function is the stimulation of gonadotrophs. Ovulation is a secondary downstream effect of the LH surge. * **Option C:** Feedback inhibition is primarily mediated by ovarian/testicular steroids (estrogen, progesterone, testosterone) acting on the hypothalamus and pituitary, not by the pulsatility of GnRH itself. * **Option D:** **Continuous (non-pulsatile)** administration of GnRH leads to the **downregulation** and desensitization of GnRH receptors. This suppresses the pituitary-gonadal axis. **Clinical Pearls for NEET-PG:** * **GnRH Agonists (e.g., Leuprolide, Goserelin):** When given continuously, they cause "chemical castration." This is used clinically to treat **prostate cancer, endometriosis, and precocious puberty**. * **Kallmann Syndrome:** Characterized by the failure of GnRH neurons to migrate, leading to hypogonadotropic hypogonadism and anosmia. * **Pulse Frequency:** High-frequency pulses favor **LH** release, while low-frequency pulses favor **FSH** release.

Q: Destruction of the zona glomerulosa will lead to a depletion of which hormone?

Aldosterone. **Explanation:** The adrenal gland is divided into an outer cortex and an inner medulla. The adrenal cortex consists of three distinct layers, often remembered by the mnemonic **"GFR"** (from superficial to deep), which correspond to the hormones they produce: **"Salt, Sugar, Sex."** 1. **Zona Glomerulosa (Outer):** Produces mineralocorticoids, primarily **Aldosterone**. This hormone regulates sodium and potassium balance. Therefore, destruction of this layer leads directly to a depletion of Aldosterone. 2. **Zona Fasciculata (Middle):** The thickest layer, responsible for producing glucocorticoids, mainly **Cortisol**. 3. **Zona Reticularis (Inner):** Produces adrenal androgens, such as **Dehydroepiandrosterone (DHEA)** and **Testosterone**. **Analysis of Incorrect Options:** * **B. Cortisol:** Produced by the Zona Fasciculata, not the Glomerulosa. * **C. Testosterone:** Produced by the Zona Reticularis (and primarily by the testes in males). * **D. Catecholamines:** These (Epinephrine and Norepinephrine) are produced by the **Adrenal Medulla** (chromaffin cells), which is embryologically derived from the neural crest, unlike the cortex. **High-Yield Clinical Pearls for NEET-PG:** * **Regulation:** The Zona Glomerulosa is primarily regulated by **Angiotensin II and Potassium levels**, whereas the Fasciculata and Reticularis are regulated by **ACTH**. * **Conn’s Syndrome:** Primary hyperaldosteronism usually caused by an adenoma in the Zona Glomerulosa. * **Addison’s Disease:** Primary adrenal insufficiency involving the destruction of all three cortical layers, leading to deficiencies in aldosterone, cortisol, and androgens.

Q: Which of the following hormones increases appetite?

Ghrelin. **Explanation:** The regulation of appetite is controlled by the arcuate nucleus of the hypothalamus, which balances **orexigenic** (appetite-stimulating) and **anorexigenic** (appetite-suppressing) signals. **Correct Option: D. Ghrelin** Ghrelin is the only major peripheral hormone that is **orexigenic**. It is secreted primarily by the P/D1 cells in the fundus of the stomach and epsilon cells of the pancreas. Ghrelin levels rise during fasting (pre-prandially) and stimulate the **NPY/AgRP neurons** in the hypothalamus to increase hunger and food intake. **Incorrect Options:** * **A. Leptin:** Produced by adipocytes, leptin is a long-term satiety signal. It inhibits NPY/AgRP neurons and stimulates POMC/CART neurons to **decrease** appetite. * **B. GLP-1:** Secreted by L-cells of the ileum and colon in response to food, it stimulates insulin secretion and acts as a potent **satiety** signal. * **C. Peptide YY (PYY):** Also secreted by L-cells of the distal small intestine and colon, it reduces appetite by inhibiting NPY release. **High-Yield Facts for NEET-PG:** * **"Hunger Hormone":** Ghrelin (G for "Growl" of the stomach). * **Sleep Deprivation:** Increases Ghrelin and decreases Leptin, leading to weight gain. * **Prader-Willi Syndrome:** Characterized by hyperphagia and obesity due to pathologically high Ghrelin levels. * **Vagus Nerve:** Ghrelin also acts via the vagal afferents to signal the brain. * **Bariatric Surgery:** Gastric bypass often leads to weight loss not just by restriction, but by significantly lowering Ghrelin production.

Q: The final cleavage products of proopiomelanocortin (POMC) are all of the following except?

Testosterone. **Explanation:** The correct answer is **Testosterone** because it is a steroid hormone synthesized from cholesterol in the Leydig cells of the testes, not a peptide derivative of Proopiomelanocortin (POMC). **Understanding POMC Cleavage:** Proopiomelanocortin (POMC) is a large precursor polypeptide synthesized primarily in the corticotrophs of the anterior pituitary and the intermediate lobe. It undergoes extensive post-translational proteolytic cleavage by enzymes called prohormone convertases to produce several biologically active peptides: * **ACTH (Adrenocorticotropic Hormone):** The primary product in the anterior pituitary. * **MSH (Melanocyte-Stimulating Hormone):** Derived from the cleavage of ACTH (α-MSH) and γ-LPH (β-MSH). This explains why hyperpigmentation occurs in Addison’s disease (high ACTH). * **Lipotropin (LPH):** Specifically β-LPH and γ-LPH, which are involved in lipid metabolism. * **Endorphins:** Specifically β-endorphin, which is derived from the cleavage of β-lipotropin and acts as an endogenous opioid. **Why other options are incorrect:** * **MSH, Lipotropin, and Endorphin** are all direct or indirect cleavage products of the POMC prohormone chain. **High-Yield Clinical Pearls for NEET-PG:** 1. **Hyperpigmentation Link:** In primary adrenal insufficiency, high levels of POMC/ACTH lead to increased α-MSH, causing characteristic skin darkening. 2. **Location Matters:** In the **Anterior Pituitary**, the main products are ACTH and β-LPH. In the **Intermediate Lobe** (and hypothalamus), these are further cleaved into MSH and Endorphins. 3. **MC4R Receptor:** α-MSH produced in the hypothalamus acts on MC4 receptors to inhibit appetite; mutations here are a common cause of monogenic obesity.

Q: TSH acts through which mechanism?

cAMP. **Explanation:** **Mechanism of Action:** Thyroid-Stimulating Hormone (TSH) is a glycoprotein hormone that acts via the **G-protein coupled receptor (GPCR)** pathway. Upon binding to its specific receptor on the thyroid follicular cell membrane, it activates the enzyme **Adenylate Cyclase**. This enzyme converts ATP into **cyclic AMP (cAMP)**, which serves as the second messenger. cAMP then activates Protein Kinase A (PKA), leading to the phosphorylation of proteins responsible for thyroid hormone synthesis (iodine trapping, thyroglobulin synthesis, and proteolysis). **Analysis of Options:** * **Option A (Ion channels):** This mechanism is typical for neurotransmitters (e.g., Acetylcholine at nicotinic receptors) or GABA, which produce rapid electrical changes, not for trophic hormones like TSH. * **Option B & D (Nuclear/Cytoplasmic receptors):** These are used by lipid-soluble hormones. **Thyroid hormones (T3/T4)** themselves act via nuclear receptors, but TSH (a peptide hormone) is water-soluble and cannot cross the lipid bilayer, necessitating a cell-surface receptor. **High-Yield Clinical Pearls for NEET-PG:** * **Second Messenger Mnemonic:** Most "stimulating" or "releasing" hormones from the pituitary (TSH, ACTH, FSH, LH, Glucagon, PTH, and V2 receptors of ADH) use the **cAMP** pathway. * **Exceptions:** Oxytocin, GnRH, and TRH use the **IP3/DAG** (Phospholipase C) pathway. * **Graves’ Disease:** This condition involves "Thyroid Stimulating Immunoglobulins" (TSI) that mimic TSH by binding to the TSH receptor and overactivating the cAMP pathway, leading to hyperthyroidism.

Question 1

Which of the following is NOT an appetite suppressant?

Accepted Answer

Neuropeptide Y

Answer

Melanocyte stimulating hormone

Answer

Melanocyte corticotropic releasing hormone

Answer

Leptin

Question 2

Calcitonin levels are increased in which of the following conditions?

Accepted Answer

Hyperparathyroidism

Answer

Hyperthyroidism

Answer

Hypoparathyroidism

Answer

Cushing Syndrome

Question 3

The blood glucose level in diabetes mellitus is decreased by the removal of which endocrine gland?

Accepted Answer

Anterior pituitary

Answer

Thyroid

Answer

Parathyroids

Answer

Posterior pituitary

Question 4

Pulsatile release of GnRH is important for?

Accepted Answer

Gonadotrophin stimulation

Answer

Ovulation induction

Answer

GnRH feedback inhibition

Answer

Gonadotropin downregulation

Question 5

Steroid hormones exert their effects by binding to which of the following?

Accepted Answer

Transcription factors

Answer

Cell surface receptors

Answer

G proteins

Answer

Cyclic adenosine monophosphate (AMP)

Question 6

All of the following developmental events are dependent on the production of maternal or fetal glucocorticoids, except?

Accepted Answer

Functional hypothalamic pituitary axis

Answer

Induction of thymic involution

Answer

Production of surfactant by type II alveolar cells

Answer

Functional thyroid

Question 7

Destruction of the zona glomerulosa will lead to a depletion of which hormone?

Accepted Answer

Aldosterone

Answer

Cortisol

Answer

Testosterone

Answer

Catecholamines

Question 8

Which of the following hormones increases appetite?

Accepted Answer

Ghrelin

Answer

Leptin

Answer

Glucagon-like peptide 1 (GLP-1)

Answer

Peptide YY (PYY)

Question 9

The final cleavage products of proopiomelanocortin (POMC) are all of the following except?

Accepted Answer

Testosterone

Answer

MSH

Answer

Lipotropin

Answer

Endorphin

Question 10

TSH acts through which mechanism?

Accepted Answer

cAMP

Answer

Ion channels

Answer

Nuclear receptors

Answer

Cytoplasmic receptors

Endocrinology — MCQs

Endocrinology — MCQs

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