Endocrinology Practice Questions

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: 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.

Q: Which of the following is NOT seen in Growth Hormone (GH) deficiency?

Hyperglycemia. **Explanation:** The correct answer is **A. Hyperglycemia**. Growth Hormone (GH) is a potent **diabetogenic hormone**. It antagonizes the action of insulin, decreases glucose uptake by peripheral tissues (anti-insulin effect), and increases hepatic gluconeogenesis. Therefore, GH deficiency leads to **hypoglycemia** (especially fasting hypoglycemia), not hyperglycemia. **Analysis of other options:** * **B. Stunting:** GH is essential for linear bone growth via the production of IGF-1 (Somatomedin C). Deficiency results in proportionate short stature or stunting. * **C. Delayed bone age:** In GH deficiency, the maturation of the skeletal system is slowed. On X-ray, the bone age is significantly lagging behind the chronological age. * **D. High-pitched voice:** GH is responsible for the growth of the larynx. Deficiency leads to a small larynx, resulting in a characteristic high-pitched or "cherubic" voice. **High-Yield Clinical Pearls for NEET-PG:** * **Laron Syndrome:** A condition of GH insensitivity due to GH receptor mutations. Features include high GH levels but low IGF-1 levels. * **Micropenis:** A common clinical sign of congenital GH deficiency in male neonates due to lack of synergistic action with androgens. * **Metabolic Effects:** GH increases lipolysis (increasing free fatty acids) and promotes protein anabolism (positive nitrogen balance). * **Screening Test:** Insulin-induced hypoglycemia is the gold standard provocative test for GH deficiency (GH levels fail to rise).

Q: Decreased activity of type I 5'-monodeiodinase could lead to which of the following physiological effects?

Increased plasma reverse T3. The thyroid gland primarily secretes **Thyroxine (T4)**, which is a pro-hormone. To become biologically active, T4 must be converted into **Triiodothyronine (T3)**. This process is mediated by **deiodinase enzymes**: 1. **Type I and Type II 5'-deiodinase:** These remove iodine from the *outer* ring of T4 to produce active **T3**. 2. **Type III deiodinase:** This removes iodine from the *inner* ring of T4 to produce inactive **reverse T3 (rT3)**. **Why Option B is Correct:** Type I 5'-monodeiodinase is responsible for the peripheral conversion of T4 to T3 and also for the **clearance (degradation) of rT3**. When the activity of this enzyme decreases, two things happen: less T4 is converted to T3, and less rT3 is broken down. This leads to a characteristic rise in plasma **reverse T3** levels. **Analysis of Incorrect Options:** * **Option A:** T3 levels would **decrease**, not increase, because the conversion from T4 is impaired [1]. * **Option C:** T4 levels usually remain **normal or slightly elevated** because its peripheral utilization/conversion is blocked. * **Option D:** TSH typically remains **normal** in these scenarios (like Euthyroid Sick Syndrome) because Type II deiodinase in the pituitary remains active, maintaining local T3 levels and feedback inhibition [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Euthyroid Sick Syndrome:** Characterized by low T3, high rT3, and normal TSH. It is the most common clinical scenario involving decreased Type I deiodinase activity (seen in starvation, trauma, or severe illness). * **Drugs inhibiting Type I deiodinase:** Propylthiouracil (PTU), Propranolol, Glucocorticoids, and Amiodarone. * **Selenium:** This trace element is a crucial cofactor for deiodinase enzymes (selenoproteins). Deficiency can impair T4 to T3 conversion.

Q: Which of the following statements is incorrect regarding melatonin?

It is secreted by the pituitary gland.. **Explanation:** The correct answer is **C**, as melatonin is **not** secreted by the pituitary gland; it is synthesized and secreted by the **pineal gland** (epiphysis cerebri). **1. Why Option C is the correct (incorrect statement) answer:** Melatonin is a derivative of the amino acid **Tryptophan**. It is produced by the pinealocytes of the pineal gland. The secretion is regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus, which acts as the body's master biological clock. The pituitary gland, conversely, secretes hormones like GH, TSH, ACTH, and LH/FSH, but not melatonin. **2. Analysis of other options:** * **Option A & B:** Melatonin is known as the "hormone of darkness." Its levels rise in the evening, promoting sleep onset and regulating the sleep-wake cycle. Clinically, exogenous melatonin is used to treat **circadian rhythm disorders**, such as insomnia and **jet lag syndrome**, to help reset the internal clock. * **Option D:** This is a factual statement. The pineal gland is the primary anatomical source of melatonin in the body. **High-Yield NEET-PG Pearls:** * **Precursor:** Tryptophan → Serotonin → Melatonin. * **Rate-limiting enzyme:** N-acetyltransferase (activity increases at night). * **Light Inhibition:** Light exposure to the retina inhibits melatonin secretion via the retinohypothalamic tract. * **Other Functions:** It is a potent antioxidant and plays a role in inhibiting reproductive function (antigonadotropic effect) in certain species by inhibiting GnRH release. * **Tumor Association:** Pineal tumors can lead to precocious puberty if they destroy the gland (removing the inhibitory effect of melatonin on gonadotropins).

Q: Which of the following findings shall be seen in a patient with hyperparathyroidism?

Hypophosphatemia. **Explanation:** The primary function of **Parathyroid Hormone (PTH)** is to maintain calcium homeostasis by increasing serum calcium levels. In **Hyperparathyroidism**, the excess secretion of PTH acts on three main target organs: the bones, the kidneys, and the intestines (indirectly). **Why Hypophosphatemia is correct:** PTH has a potent **phosphaturic effect**. It acts on the proximal convoluted tubules (PCT) of the kidney to inhibit the sodium-phosphate cotransporter (NaPi-IIa). This leads to a decrease in the reabsorption of phosphate, causing increased urinary excretion of phosphate (**phosphaturia**) and a subsequent decrease in serum phosphate levels (**Hypophosphatemia**). **Analysis of Incorrect Options:** * **B. Hyperphosphatemia:** This is typically seen in *Hypoparathyroidism* or Chronic Kidney Disease (CKD). In hyperparathyroidism, the kidney is actively "wasting" phosphate. * **C & D. Magnesium levels:** While PTH can slightly increase magnesium reabsorption in the distal tubule, magnesium levels are not a primary diagnostic hallmark of hyperparathyroidism. In fact, chronic hyperparathyroidism can sometimes lead to mild *hypomagnesemia* due to associated hypercalciuria, but **Hypophosphatemia** is the classic, high-yield biochemical finding. **NEET-PG High-Yield Pearls:** 1. **Biochemical Triad:** Hypercalcemia + Hypophosphatemia + Hypercalciuria (the latter occurs because the filtered load of calcium exceeds the kidney's reabsorptive capacity). 2. **Bone Finding:** *Osteitis fibrosa cystica* (subperiosteal bone resorption, especially in phalanges). 3. **Renal Finding:** PTH stimulates **1-alpha-hydroxylase** in the kidneys, increasing the production of active Vitamin D [1,25(OH)₂D]. 4. **Mnemonic:** "Stones, bones, abdominal groans, and psychic overtones."

Question 1

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 2

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

Accepted Answer

Pituitary gland

Answer

Ovary

Answer

Corpus luteum

Answer

Hypothalamus

Question 3

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 4

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 5

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

Question 6

Which of the following is NOT seen in Growth Hormone (GH) deficiency?

Accepted Answer

Hyperglycemia

Answer

Stunting

Answer

Delayed bone age

Answer

High pitched voice

Question 7

Decreased activity of type I 5'-monodeiodinase could lead to which of the following physiological effects?

Accepted Answer

Increased plasma reverse T3

Answer

Increased plasma triiodothyronine (T3)

Answer

Decreased plasma thyroxine T4

Answer

Increased TSH

Question 8

Which of the following statements is incorrect regarding melatonin?

Accepted Answer

It is secreted by the pituitary gland.

Answer

It induces sleep.

Answer

It is used in the treatment of jet lag syndrome.

Answer

It is a pineal hormone.

Question 9

Which of the following findings shall be seen in a patient with hyperparathyroidism?

Accepted Answer

Hypophosphatemia

Answer

Hyperphosphatemia

Answer

Hypermagnesemia

Answer

Hypomagnesemia

Question 10

What is the primary action of estrogen on bone?

Accepted Answer

Acts as an antiresorptive agent on trabecular bone

Answer

Stimulates bone matrix deposition

Answer

Has an anti-osteoblastic effect on compact bone

Answer

Acts as a resorptive agent on compact bone

Endocrinology — MCQs

Endocrinology — MCQs

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