Endocrinology Practice Questions

Q: Which of the following hormones is NOT produced by the endocrine part of the pancreas?

Bombesin. **Explanation:** The pancreas is a dual-function organ consisting of an exocrine part (acini) and an endocrine part (Islets of Langerhans). The Islets of Langerhans contain several distinct cell types that secrete specific hormones directly into the bloodstream. **Why Bombesin is the correct answer:** Bombesin is a peptide originally isolated from the skin of amphibians. In humans, its equivalent is **Gastrin-Releasing Peptide (GRP)**. It is primarily found in the gastrointestinal tract and the brain, acting as a neurotransmitter and a stimulator of gastrin release. It is **not** a product of the pancreatic Islets of Langerhans. **Why the other options are incorrect:** * **Insulin (Option A):** Produced by the **Beta (β) cells**, which make up about 60-75% of the islet cells. It is the primary anabolic hormone responsible for lowering blood glucose. * **Somatostatin (Option B):** Produced by the **Delta (δ) cells** (approx. 5-10%). It acts locally (paracrine effect) to inhibit the secretion of both insulin and glucagon. * **Glucagon (Option C):** Produced by the **Alpha (α) cells** (approx. 20%). It is a catabolic hormone that increases blood glucose levels via glycogenolysis and gluconeogenesis. **High-Yield Clinical Pearls for NEET-PG:** * **Cell Distribution:** Remember the mnemonic **"BAGS"** for islet cells: **B**eta (Insulin), **A**lpha (Glucagon), **G**amma/PP cells (Pancreatic Polypeptide), and **S**igma/Delta (Somatostatin). * **Epsilon (ε) cells:** A minor cell type in the pancreas that produces **Ghrelin** (the hunger hormone). * **Blood Flow Pattern:** Blood in the islets flows from the center (Beta cells) to the periphery (Alpha/Delta cells), allowing insulin to inhibit glucagon release directly.

Q: Which of the following can result in the secretion of both insulin and glucagon?

Arginine. **Explanation:** The secretion of insulin and glucagon is typically reciprocal (one increases while the other decreases) to maintain glucose homeostasis. However, **Arginine** (and other amino acids like lysine) is a unique potent stimulator for **both** hormones. 1. **Why Arginine is Correct:** When a protein-rich meal is consumed, amino acids stimulate **insulin** to promote protein synthesis and glucose uptake. Simultaneously, they stimulate **glucagon** secretion. This "protective" glucagon release prevents hypoglycemia that might otherwise occur if insulin acted alone in the absence of dietary carbohydrates (the "protein-induced hypoglycemia" prevention mechanism). 2. **Why Incorrect Options are Wrong:** * **Fatty Acids:** High levels of free fatty acids primarily stimulate insulin secretion but generally inhibit glucagon. * **Hypoglycemia:** Low blood glucose is the primary stimulus for **glucagon** but strongly inhibits insulin secretion to prevent further glucose drop. * **Hyperglycemia:** High blood glucose is the primary stimulus for **insulin** but inhibits glucagon secretion via paracrine effects (somatostatin and intra-islet insulin). **NEET-PG High-Yield Pearls:** * **Biphasic Response:** Insulin secretion is biphasic; the first phase is the release of pre-formed granules, and the second is the synthesis of new insulin. * **Incretin Effect:** Oral glucose causes a much higher insulin response than intravenous glucose due to GIP and GLP-1 (Incretins). * **Major Inhibitor:** Somatostatin (from Delta cells) inhibits the secretion of both insulin and glucagon. * **Adrenergic Effect:** Alpha-2 stimulation inhibits insulin, while Beta-2 stimulation increases it.

Q: Luteinizing hormone (LH) is secreted by which endocrine gland?

Pituitary gland. **Explanation:** Luteinizing Hormone (LH) is a gonadotropin synthesized and secreted by the **gonadotroph cells** of the **Anterior Pituitary Gland**. Its release is stimulated by the pulsatile secretion of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus. In females, LH triggers ovulation and maintains the corpus luteum; in males, it stimulates Leydig cells to produce testosterone. **Analysis of Options:** * **Pituitary Gland (Correct):** Specifically, the anterior lobe (adenohypophysis) produces LH and FSH. These are glycoprotein hormones consisting of an alpha subunit (common to TSH and hCG) and a hormone-specific beta subunit. * **Ovary (Incorrect):** The ovary is the target organ for LH, not the source. It produces steroid hormones like estrogen and progesterone in response to LH stimulation. * **Corpus Luteum (Incorrect):** This is a temporary endocrine structure formed in the ovary *after* ovulation (triggered by the LH surge). It primarily secretes progesterone. * **Hypothalamus (Incorrect):** The hypothalamus acts as the "master controller" by secreting **GnRH**, which then signals the pituitary to release LH. **High-Yield Clinical Pearls for NEET-PG:** * **The LH Surge:** A positive feedback loop of Estrogen leads to a massive release of LH, which is the immediate trigger for **ovulation** (occurring ~24–36 hours after the surge). * **Alpha Subunit:** LH, FSH, TSH, and hCG share an identical alpha subunit. Specificity is determined by the **beta subunit**. * **LH:FSH Ratio:** An elevated ratio (>2:1 or 3:1) is a classic biochemical marker for **Polycystic Ovary Syndrome (PCOS)**. * **Leydig Cells:** In males, LH is often called Interstitial Cell Stimulating Hormone (ICSH).

Q: A 30-year-old male presents with recurrent attacks of sweating and dizziness. Further workup reveals low blood glucose levels with inappropriately elevated insulin and C-peptide levels. Imaging shows a lesion in the pancreas. He is diagnosed with insulinoma and given diazoxide. What is the mechanism of action of diazoxide?

Opening of ATP-sensitive K+ channels. **Explanation:** **Correct Option: A (Opening of ATP-sensitive K+ channels)** In the normal physiology of insulin secretion, glucose enters pancreatic beta cells and increases the ATP/ADP ratio. This causes the **ATP-sensitive K+ channels ($K_{ATP}$)** to close, leading to cell depolarization, calcium influx, and insulin release. **Diazoxide** acts as a **$K_{ATP}$ channel opener**. By keeping these channels open, it allows potassium to exit the cell (hyperpolarization). This prevents the opening of voltage-gated calcium channels, thereby inhibiting the exocytosis of insulin. In patients with insulinoma, diazoxide is used to manage hypoglycemia by suppressing this excessive insulin secretion. **Incorrect Options:** * **B (Closing of ATP-sensitive K+ channels):** This is the mechanism of **Sulfonylureas** (e.g., Glibenclamide). Closing these channels triggers insulin release, which would worsen hypoglycemia in an insulinoma patient. * **C (Increase in GLUT-4 receptors):** This is the mechanism of **Thiazolidinediones** (e.g., Pioglitazone) and is also a secondary effect of exercise and insulin. It increases peripheral glucose uptake but does not address the primary pathology of hyperinsulinism. * **D (Opening of voltage-sensitive Ca+2 channels):** This occurs downstream of $K_{ATP}$ channel closure and directly triggers insulin release. Diazoxide indirectly prevents this step. **NEET-PG High-Yield Pearls:** * **Insulinoma Triad (Whipple’s Triad):** Hypoglycemic symptoms, low plasma glucose (<50 mg/dL), and relief of symptoms after glucose administration. * **C-peptide:** Elevated in insulinoma (endogenous production) but low/absent in exogenous insulin surreptitious use. * **Other uses of Diazoxide:** It was historically used as an IV vasodilator for hypertensive emergencies (though rarely used now due to side effects like sodium retention and hypertrichosis).

Q: Which hormone, along with insulin, is produced by the beta cells of the pancreas?

Both Amylin and C-peptide. ### Explanation **Correct Answer: C. Both Amylin and C-peptide** **1. Why the answer is correct:** The beta cells of the Islets of Langerhans are responsible for synthesizing and secreting insulin. However, this process involves the co-secretion of two other important molecules: * **C-peptide (Connecting peptide):** Insulin is synthesized as a precursor called **proinsulin**. Inside the secretory granules, proinsulin is cleaved by endopeptidases into equimolar amounts of mature insulin and C-peptide. Therefore, for every molecule of insulin released into the portal circulation, one molecule of C-peptide is also released. * **Amylin (Islet Amyloid Polypeptide - IAPP):** This is a 37-amino acid peptide hormone that is stored in the same secretory granules as insulin and is co-released in response to nutrient stimuli (though in much smaller quantities, roughly 1:100 ratio). Amylin functions to slow gastric emptying and promote satiety. **2. Why other options are incorrect:** * **Option A & B:** While both are produced by beta cells, selecting either individually is incomplete. Since both are co-secreted with insulin, Option C is the most accurate choice. **3. High-Yield Clinical Pearls for NEET-PG:** * **C-peptide Clinical Utility:** Unlike insulin, C-peptide undergoes negligible first-pass metabolism by the liver and has a longer half-life. It is used as a **marker of endogenous insulin production**. It helps distinguish Type 1 DM (low/absent C-peptide) from Type 2 DM (normal/high C-peptide) and is used in the workup of insulinoma. * **Amylin & Pathology:** In Type 2 Diabetes, amylin can aggregate to form **amyloid deposits** in the pancreas, which is a classic histopathological finding. * **Pramlintide:** This is a synthetic analogue of amylin used as an adjunct treatment in both Type 1 and Type 2 DM to control postprandial glucose.

Q: What are the metabolic effects of insulin on adipose tissue?

Accelerated transport of glucose. ### Explanation Insulin is an anabolic hormone that promotes energy storage. In adipose tissue, its primary role is to facilitate glucose uptake and promote lipogenesis while inhibiting lipolysis. **Why Option A is Correct:** Insulin stimulates the **GLUT-4** (glucose transporter type 4) translocation from intracellular vesicles to the plasma membrane of adipocytes. This leads to the **accelerated transport of glucose** into the cell. Once inside, glucose provides the glycerol backbone (via α-glycerophosphate) necessary for the esterification of fatty acids into triglycerides. **Analysis of Incorrect Options:** * **B. Decreased glucose phosphorylation:** Incorrect. Insulin actually **increases** glucose phosphorylation by stimulating **hexokinase**, ensuring that glucose entering the cell is trapped and utilized for metabolism. * **C. Decreased lipoprotein lipase:** Incorrect. Insulin **increases** the activity of **endothelial lipoprotein lipase (LPL)**. This enzyme breaks down circulating chylomicrons and VLDLs into free fatty acids, which are then taken up by adipocytes for storage. * **D. Increased cyclic AMP:** Incorrect. Insulin **decreases** intracellular cAMP levels by activating phosphodiesterase. Lower cAMP levels inhibit **hormone-sensitive lipase (HSL)**, thereby decreasing lipolysis (the breakdown of stored fat). **NEET-PG High-Yield Pearls:** * **GLUT-4** is the only insulin-dependent glucose transporter; it is found specifically in **adipose tissue and skeletal muscle**. * Insulin is the most potent **antilipolytic hormone** because it inhibits hormone-sensitive lipase. * In **Diabetes Mellitus**, insulin deficiency leads to increased HSL activity, resulting in high levels of circulating free fatty acids and potential ketoacidosis.

Q: Which of the following decreases the secretion of both insulin and glucagon?

Somatostatin. ### Explanation The correct answer is **Somatostatin**. **Mechanism of Action:** Somatostatin is a potent inhibitory hormone produced by the **delta ($\delta$) cells** of the pancreatic islets (as well as the hypothalamus and GI tract). In the pancreas, it acts via **paracrine signaling** to inhibit the secretion of both **Insulin** (from beta cells) and **Glucagon** (from alpha cells). It acts through G-protein coupled receptors (SSTRs) that decrease intracellular cAMP and inhibit calcium influx, effectively "shutting down" islet cell output. **Analysis of Incorrect Options:** * **Epinephrine:** Stimulates glucagon secretion (to increase blood glucose for "fight or flight") but **inhibits** insulin secretion (primarily via $\alpha_2$-adrenergic receptors). It does not decrease both. * **Increased blood glucose:** This is the primary physiological stimulus for **insulin** secretion. While it inhibits glucagon, it significantly increases insulin levels. * **None of the above:** Incorrect, as Somatostatin is the classic "universal inhibitor." **NEET-PG High-Yield Pearls:** * **The "Universal Inhibitor":** Somatostatin inhibits not only pancreatic hormones but also Growth Hormone (GH), Thyroid Stimulating Hormone (TSH), and various GI hormones (Gastrin, CCK, Secretin). * **Clinical Application:** **Octreotide**, a synthetic somatostatin analog, is used clinically to treat acromegaly, carcinoid tumors, and acute variceal bleeding (by reducing splanchnic blood flow). * **Islet Cell Arrangement:** Remember the flow of blood in the islet is usually from the center (Beta cells) to the periphery (Alpha/Delta cells), allowing insulin to inhibit glucagon directly.

Question 1

Inappropriate ADH secretion is characterised by all of the following except?

Accepted Answer

Hypo-osmolar urine

Answer

Water intoxication

Answer

Expanded fluid volume

Answer

Hypomagnesemia

Question 2

Which of the following hormones is NOT produced by the endocrine part of the pancreas?

Accepted Answer

Bombesin

Answer

Insulin

Answer

Somatostatin

Answer

Glucagon

Question 3

Continuous administration of testosterone leads to which of the following conditions?

Accepted Answer

Azoospermia

Answer

Increased sperm motility

Answer

Increased spermatogenesis

Answer

Increased gonadotrophins

Question 4

Which of the following is not controlled by the autonomic nervous system?

Accepted Answer

Aldosterone

Answer

Insulin

Answer

Growth Hormone (GH)

Answer

Somatostatin

Question 5

Which of the following can result in the secretion of both insulin and glucagon?

Accepted Answer

Arginine

Answer

Fatty acids

Answer

Hypoglycemia

Answer

Hyperglycemia

Question 6

Luteinizing hormone (LH) is secreted by which endocrine gland?

Accepted Answer

Pituitary gland

Answer

Ovary

Answer

Corpus luteum

Answer

Hypothalamus

Question 7

A 30-year-old male presents with recurrent attacks of sweating and dizziness. Further workup reveals low blood glucose levels with inappropriately elevated insulin and C-peptide levels. Imaging shows a lesion in the pancreas. He is diagnosed with insulinoma and given diazoxide. What is the mechanism of action of diazoxide?

Accepted Answer

Opening of ATP-sensitive K+ channels

Answer

Closing of ATP-sensitive K+ channels

Answer

Increase in the number of GLUT-4 receptors

Answer

Opening of voltage-sensitive Ca+2 channels

Question 8

Which hormone, along with insulin, is produced by the beta cells of the pancreas?

Accepted Answer

Both Amylin and C-peptide

Answer

Amylin

Answer

C-peptide

Answer

Neither Amylin nor C-peptide

Question 9

What are the metabolic effects of insulin on adipose tissue?

Accepted Answer

Accelerated transport of glucose

Answer

Decreased glucose phosphorylation

Answer

Decreased lipoprotein lipase

Answer

Increased cyclic AMP

Question 10

Which of the following decreases the secretion of both insulin and glucagon?

Accepted Answer

Somatostatin

Answer

Epinephrine

Answer

Increased blood glucose

Answer

None of the above

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?