Endocrinology Practice Questions

Q: Which of the following pituitary hormones does NOT decrease the stimulatory control of the pituitary?

Prolactin. ### Explanation The regulation of the pituitary gland primarily follows a **negative feedback mechanism**. In most endocrine axes, the pituitary hormone (or the peripheral hormone it stimulates) inhibits the hypothalamus to decrease further stimulation. **Why Prolactin is the Correct Answer:** Unlike most anterior pituitary hormones, **Prolactin** is unique because it is under **tonic inhibitory control** by the hypothalamus via **Dopamine** (Prolactin-Inhibiting Hormone). Prolactin does not decrease the "stimulatory control" because its primary regulator is an inhibitor. When Prolactin levels rise, they stimulate the hypothalamus to increase the secretion of Dopamine, which further *inhibits* the pituitary. It lacks a classic stimulatory releasing hormone (like TRH or GnRH) as its primary regulator. **Analysis of Incorrect Options:** * **FSH and LH (Options B & C):** These gonadotropins are regulated by **GnRH** (Gonadotropin-Releasing Hormone). Through the "short-loop" feedback mechanism, high levels of FSH and LH inhibit the hypothalamus, decreasing the stimulatory release of GnRH. * **Oxytocin (Option D):** While Oxytocin is known for **positive feedback** (e.g., Ferguson reflex during labor), in the context of the hypothalamic-pituitary axis, it does not function under a tonic inhibitory tone like Prolactin. **High-Yield Clinical Pearls for NEET-PG:** * **Dopamine is the primary Prolactin-Inhibiting Hormone (PIH).** Any drug that blocks Dopamine (e.g., Antipsychotics like Haloperidol or Metoclopramide) will cause **Hyperprolactinemia**. * **Stalk Effect:** Damage to the pituitary stalk interrupts the flow of Dopamine to the anterior pituitary, leading to a decrease in all pituitary hormones *except* Prolactin, which rises. * **TRH (Thyrotropin-Releasing Hormone)** can act as a minor prolactin-releasing factor; hence, patients with primary hypothyroidism (high TRH) often present with galactorrhea.

Q: Proopiomelanocortin is released from which gland?

Hypothalamus. **Explanation:** **Proopiomelanocortin (POMC)** is a large precursor polypeptide synthesized primarily in the **corticotrophs of the anterior pituitary** and the **arcuate nucleus of the Hypothalamus**. In the hypothalamus, POMC neurons play a critical role in energy homeostasis; they are processed into **α-MSH** (alpha-melanocyte-stimulating hormone), which acts on MC3/MC4 receptors to inhibit food intake (anorexigenic effect). **Analysis of Options:** * **A. Hypothalamus (Correct):** As mentioned, POMC is synthesized in the arcuate nucleus. It is also produced in the anterior pituitary (precursor to ACTH) and the intermediate lobe of the pituitary. * **B. Liver:** The liver is involved in the synthesis of proteins like albumin, clotting factors, and Angiotensinogen, but it does not produce POMC. * **C. Adrenal:** The adrenal cortex is the *target* for ACTH (a derivative of POMC), where it stimulates cortisol production. It does not synthesize the POMC precursor itself. * **D. Lung:** While small cell carcinoma of the lung can produce ACTH ectopically (paraneoplastic syndrome), the lung is not a physiological site of POMC release. **High-Yield Clinical Pearls for NEET-PG:** 1. **Post-translational Processing:** POMC is cleaved by **Prohormone Convertases (PC1 and PC2)**. PC1 leads to ACTH production (Pituitary), while PC2 leads to α-MSH production (Hypothalamus). 2. **Derivatives:** POMC is the parent molecule for **ACTH, β-endorphin, α-MSH, and γ-LPH**. 3. **Hyperpigmentation:** In Addison’s disease, high levels of POMC/ACTH lead to skin hyperpigmentation because ACTH shares a structural sequence with MSH and can bind to melanocortin-1 receptors. 4. **Appetite Regulation:** Leptin stimulates POMC neurons in the hypothalamus to decrease appetite. Mutations in the POMC gene can lead to early-onset severe obesity.

Q: Which adrenergic beta receptor has a role in lipolysis in fat cells?

Beta 3. **Explanation:** The correct answer is **Beta 3 (Option D)**. Adrenergic receptors are G-protein coupled receptors (GPCRs) that mediate the effects of catecholamines. The **Beta-3 ($\beta_3$) receptor** is primarily located in **adipose tissue** (both brown and white fat). When stimulated by norepinephrine, it activates the $G_s$ protein-adenylyl cyclase pathway, increasing intracellular cAMP. This activates Protein Kinase A, which phosphorylates **hormone-sensitive lipase (HSL)**, leading to the breakdown of triglycerides into free fatty acids and glycerol (**lipolysis**). In brown adipose tissue, $\beta_3$ stimulation also promotes thermogenesis via Uncoupling Protein 1 (UCP1/Thermogenin). **Analysis of Incorrect Options:** * **Alpha 1 ($\alpha_1$):** Linked to $G_q$ proteins; primarily causes smooth muscle contraction (vasoconstriction, pupillary dilation, and intestinal sphincter contraction). * **Alpha 2 ($\alpha_2$):** Linked to $G_i$ proteins; acts as a presynaptic autoreceptor to inhibit norepinephrine release. In fat cells, $\alpha_2$ stimulation actually **inhibits** lipolysis (antagonistic to $\beta_3$). * **Beta 1 ($\beta_1$):** Primarily located in the **heart** (increases heart rate and contractility) and the juxtaglomerular apparatus of the kidney (increases renin release). **High-Yield Clinical Pearls for NEET-PG:** * **Mirabegron:** A selective $\beta_3$ agonist used clinically for the treatment of **overactive bladder** (causes detrusor muscle relaxation). * **Lipolysis hierarchy:** While $\beta_3$ is the classic answer for fat cells, $\beta_1$ also contributes to lipolysis in humans, but $\beta_3$ is the specific "metabolic" receptor often tested. * **Mnemonic:** $\beta_1$ (1 Heart), $\beta_2$ (2 Lungs), $\beta_3$ (3 letters in FAT).

Q: All of the following hormones are increased during stress except?

Insulin. **Explanation:** The body’s response to stress (the "fight or flight" response) is designed to mobilize energy substrates—primarily glucose and free fatty acids—to meet increased metabolic demands. This is achieved through the activation of the **Sympathetic Nervous System (SNS)** and the **Hypothalamic-Pituitary-Adrenal (HPA) axis**. **Why Insulin is the correct answer:** Insulin is an **anabolic hormone** that promotes glucose storage (glycogenesis) and uptake into peripheral tissues. During stress, the body needs to maintain high blood glucose levels for the brain and muscles. Therefore, insulin secretion is **inhibited** by the sympathetic nervous system (via $\alpha_2$-adrenergic receptors on pancreatic beta cells). This state of "stress-induced hyperglycemia" ensures glucose availability. **Why the other options are incorrect:** * **Cortisol (Option A):** Known as the primary "stress hormone," it increases gluconeogenesis and protein catabolism to provide energy during prolonged stress. * **Adrenaline & Noradrenaline (Options C & D):** These catecholamines are released immediately during acute stress. They stimulate glycogenolysis in the liver and lipolysis in adipose tissue to rapidly elevate blood glucose and fatty acid levels. **NEET-PG High-Yield Pearls:** * **Glucagon and Growth Hormone** are also increased during stress; both are "counter-regulatory" hormones that oppose insulin action. * **Catecholamine effect on Insulin:** While $\beta_2$ stimulation can increase insulin, the **$\alpha_2$ inhibitory effect predominates** during stress, leading to a net decrease in insulin levels. * **ADH (Vasopressin):** Also increases during stress to maintain blood pressure and fluid volume.

Q: Insulin secretion is decreased by which of the following hormones?

Somatostatin. **Explanation:** The regulation of insulin secretion is a complex process involving nutrients, autonomic nerves, and gastrointestinal hormones. **Why Somatostatin is correct:** Somatostatin, secreted by the **Delta (δ) cells** of the pancreatic islets, acts as a potent universal inhibitor. It exerts a **paracrine effect** on neighboring Beta (β) cells to **decrease insulin secretion** and on Alpha (α) cells to decrease glucagon secretion. It acts via G-protein coupled receptors (SSTR-2 and SSTR-5) which decrease intracellular cAMP and inhibit calcium influx, thereby preventing exocytosis of insulin granules. **Why the other options are incorrect:** * **Glucagon:** While it has the opposite metabolic effect of insulin, glucagon actually **stimulates** insulin secretion. This ensures that as glucagon mobilizes glucose into the bloodstream, insulin is available to facilitate its utilization by peripheral tissues. * **Gastrin and Secretin:** These are gastrointestinal hormones (Incretins/Enterogastrones). The "Incretin effect" describes how oral glucose causes a higher insulin response than intravenous glucose. Gastrin, Secretin, CCK, and GIP all act to **increase** insulin secretion in anticipation of rising blood glucose levels following a meal. **High-Yield Clinical Pearls for NEET-PG:** * **Most potent stimulator** of insulin: Glucose. * **Most potent inhibitor** of insulin: Somatostatin (Physiological) and Epinephrine (via α2 receptors during stress). * **Incretin Effect:** Primarily mediated by **GLP-1** (Glucagon-like peptide-1) and **GIP** (Glucose-dependent insulinotropic peptide). * **Drug Link:** Octreotide is a synthetic somatostatin analogue used clinically to treat insulinomas and acromegaly due to its inhibitory properties.

Q: Which of the following hormones is NOT secreted by the anterior pituitary?

Oxytocin. **Explanation:** The pituitary gland (hypophysis) is divided into the **Anterior Pituitary (Adenohypophysis)** and the **Posterior Pituitary (Neurohypophysis)**. The key distinction lies in their embryology and function: the anterior pituitary synthesizes its own hormones, whereas the posterior pituitary only stores and releases hormones produced in the hypothalamus. **Why Oxytocin is the Correct Answer:** Oxytocin is synthesized in the **paraventricular nuclei** (and to a lesser extent, the supraoptic nuclei) of the **hypothalamus**. It travels down the hypothalamo-hypophyseal tract to be stored in the posterior pituitary. Therefore, the posterior pituitary *releases* but does *not* secrete (synthesize) oxytocin. **Analysis of Incorrect Options:** * **Growth Hormone (GH):** Secreted by **Somatotrophs** in the anterior pituitary. It is the most abundant anterior pituitary hormone. * **FSH (Follicle-Stimulating Hormone):** A gonadotropin secreted by **Gonadotrophs** in the anterior pituitary. * **Prolactin:** Secreted by **Lactotrophs** (Mammotrophs) in the anterior pituitary. Unlike other hormones, its primary regulation is inhibitory (via Dopamine). **High-Yield NEET-PG Pearls:** 1. **Posterior Pituitary Hormones:** Only two—**Oxytocin** and **ADH (Vasopressin)**. Both are synthesized in the hypothalamus. 2. **Embryology:** The anterior pituitary develops from **Rathke’s pouch** (ectodermal outpocketing of the oropharynx), while the posterior pituitary develops from the **neuroectoderm** of the floor of the third ventricle. 3. **Cell Types:** Acidophils (GH, Prolactin) and Basophils (FSH, LH, ACTH, TSH). Remember the mnemonic: **"B-FLAT"** for Basophils.

Question 1

Estrogen receptors are typically located in which cellular compartment?

Accepted Answer

Nucleus

Answer

Microsomes

Answer

Membrane-bound organelles

Answer

Mitochondria

Question 2

Which of the following pituitary hormones does NOT decrease the stimulatory control of the pituitary?

Accepted Answer

Prolactin

Answer

Follicle-stimulating hormone (FSH)

Answer

Luteinizing hormone (LH)

Answer

Oxytocin

Question 3

Proopiomelanocortin is released from which gland?

Accepted Answer

Hypothalamus

Answer

Liver

Answer

Adrenal

Answer

Lung

Question 4

Which adrenergic beta receptor has a role in lipolysis in fat cells?

Accepted Answer

Beta 3

Answer

Alpha 1

Answer

Alpha 2

Answer

Beta 1

Question 5

All of the following hormones are increased during stress except?

Accepted Answer

Insulin

Answer

Cortisol

Answer

Adrenaline

Answer

Noradrenaline

Question 6

Insulin secretion is decreased by which of the following hormones?

Accepted Answer

Somatostatin

Answer

Glucagon

Answer

Gastrin

Answer

Secretin

Question 7

Which of the following hormones is NOT secreted by the anterior pituitary?

Accepted Answer

Oxytocin

Answer

Growth hormone

Answer

FSH

Answer

Prolactin

Question 8

What is the mechanism of action of Calcitriol?

Accepted Answer

Increased calcium absorption from the intestine

Answer

Decreased calcium resorption from bone

Answer

Decreased calcium absorption from the kidney

Answer

Decreased calcium absorption from the intestine

Question 9

Posterior pituitary hormone secretion is mediated by which of the following mechanisms?

Accepted Answer

The hypothalamo-hypophyseal tract originating from magnocellular neurons in the supraoptic and paraventricular nuclei

Answer

A portal capillary system from the hypothalamus to the posterior pituitary

Answer

The fight-or-flight response

Answer

The reticular activating system's input to the hypothalamus

Question 10

Increased blood levels of cholesterol seen in hypothyroidism are most likely due to which of the following mechanisms?

Accepted Answer

Decreased production of LDL receptors in adipose tissue and increased release of cholesterol from adipose tissue

Answer

Decreased calorigenesis

Answer

Decreased production of LDL receptors in the liver, leading to decreased hepatic clearance

Answer

Increased breakdown of lipoproteins releasing cholesterol into circulation

Endocrinology — MCQs

Endocrinology — MCQs

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