Endocrinology Practice Questions

Q: Which of the following is NOT a stimulus for insulin secretion?

Hypokalemia. **Explanation:** Insulin secretion from the pancreatic beta cells is a highly regulated process. The correct answer is **Hypokalemia** because low serum potassium levels actually **inhibit** insulin release. **1. Why Hypokalemia is the correct answer:** The mechanism of insulin secretion depends on the closure of ATP-sensitive $K^+$ channels, leading to cell depolarization and calcium influx. In **hypokalemia**, the cell membrane becomes hyperpolarized (more negative), making it harder for the cell to depolarize. This inhibits the release of insulin, which can clinically manifest as glucose intolerance in patients with low potassium levels. **2. Why the other options are stimuli for insulin:** * **Glucagon (A):** Glucagon acts via a paracrine mechanism to directly stimulate beta cells to secrete insulin. This ensures that as glucagon raises blood glucose, insulin is available to facilitate glucose uptake. * **Ketone bodies (C):** Elevated levels of ketones (like acetoacetate) act as a feedback signal to stimulate insulin, which in turn inhibits further lipolysis and ketogenesis, preventing ketoacidosis in healthy individuals. * **Amino acids (D):** Arginine and Lysine are potent stimulators of insulin secretion. They depolarize the beta cell membrane directly or via co-transport with sodium. **Clinical Pearls for NEET-PG:** * **The "Incretin Effect":** Oral glucose causes a much greater insulin response than IV glucose due to the release of GIP and GLP-1 from the gut. * **Potassium Connection:** Insulin therapy causes an intracellular shift of potassium. Therefore, always monitor for hypokalemia when treating Diabetic Ketoacidosis (DKA) with insulin. * **Drug Correlation:** Sulfonylureas stimulate insulin by blocking the same ATP-sensitive $K^+$ channels mentioned above.

Q: What is the effect of cortisol?

Decreased bone matrix. **Explanation:** Cortisol (the primary glucocorticoid) has profound effects on bone metabolism and hematology. **Why Option A is Correct:** Cortisol causes a **decrease in bone matrix** through several mechanisms. It inhibits **osteoblast** (bone-forming cell) activity and protein synthesis (collagen type I), while simultaneously stimulating **osteoclast** (bone-resorbing cell) activity. Furthermore, cortisol decreases intestinal calcium absorption and increases renal calcium excretion, leading to secondary hyperparathyroidism, which further accelerates bone loss. This is why chronic steroid use is a major risk factor for osteoporosis. **Analysis of Incorrect Options:** * **Option B:** Incorrect, as cortisol is catabolic to bone and connective tissue. * **Option C:** Incorrect. Cortisol causes **lymphocytopenia**, eosinopenia, and monocytopenia by sequestering these cells into the spleen and bone marrow and inducing apoptosis in T-cells. * **Option D:** While cortisol does stimulate erythropoiesis (increasing RBC count), it is not the classic "textbook" primary effect often tested in the context of bone matrix pathology. However, in many competitive exams, if "Decreased bone matrix" is an option, it is prioritized due to its significant clinical implication in Cushing’s syndrome. **NEET-PG High-Yield Pearls:** * **Hematological "Rule of Thumb":** Cortisol **increases** "B-N-P" (Blood pressure, Neutrophils, Platelets/RBCs) and **decreases** "L-E-M" (Lymphocytes, Eosinophils, Monocytes). * **Neutrophilia:** Cortisol causes neutrophilia by decreasing the "marginal pool" (preventing neutrophils from sticking to vessel walls). * **Cushing’s Syndrome:** Characterized by osteoporosis, pathological fractures, and "buffalo hump" due to fat redistribution despite muscle wasting (proteolysis).

Q: Which of the following is NOT an effect of the T3 hormone?

It decreases pulse pressure. **Explanation:** The thyroid hormone (T3) has profound effects on the cardiovascular system, primarily acting to increase cardiac output and meet the body's metabolic demands. **Why Option D is the Correct Answer:** T3 **increases pulse pressure**, it does not decrease it. Pulse pressure is the difference between systolic blood pressure (SBP) and diastolic blood pressure (DBP). T3 increases SBP (due to increased stroke volume and contractility) and decreases DBP (due to vasodilation). This widening of the gap results in a **wide pulse pressure**, a classic clinical sign of hyperthyroidism. **Analysis of Incorrect Options:** * **A. Increases Heart Rate:** T3 has a direct chronotropic effect by upregulating $\beta_1$-adrenergic receptors in the heart and increasing the rate of depolarization in the SA node. * **B. Increases Stroke Volume:** T3 exerts a positive inotropic effect by increasing the expression of $\alpha$-myosin heavy chains and SERCA (sarcoplasmic reticulum calcium ATPase), enhancing myocardial contractility and stroke volume. * **C. Decreases Peripheral Resistance:** T3 causes direct vasodilation of peripheral arterioles by increasing local metabolic end-products and decreasing systemic vascular resistance (SVR). **NEET-PG High-Yield Pearls:** * **Hyperthyroidism:** Characterized by tachycardia, palpitations, and a "bounding pulse" (due to wide pulse pressure). * **Hypothyroidism:** Characterized by bradycardia and a "narrow pulse pressure." * **Molecular Mechanism:** T3 increases the transcription of the **SERCA2 pump**, which improves calcium sequestration during diastole, leading to faster relaxation (lusitropic effect) and stronger subsequent contraction.

Q: A middle-aged man notices that he can no longer fit in his shoes and observes enlargement of his jaw and phalanges. Which hormone mediates these effects?

Somatomedin. ### Explanation The clinical presentation of increasing shoe size, jaw enlargement (prognathism), and phalangeal thickening in an adult is classic for **Acromegaly**, which results from the hypersecretion of Growth Hormone (GH) after epiphyseal closure [2]. **Why Somatomedin is Correct:** While GH is the primary hormone secreted by the pituitary adenoma, its peripheral effects—especially linear and bony growth—are mediated by **Somatomedin C**, also known as **Insulin-like Growth Factor 1 (IGF-1)** [1]. GH stimulates the liver to produce IGF-1, which then acts on tissues to promote protein synthesis and skeletal growth [1]. In clinical practice, measuring serum IGF-1 is the most reliable screening test for Acromegaly because it has a longer half-life and lacks the pulsatile secretion pattern of GH [3]. **Why the Other Options are Incorrect:** * **ACTH (A):** Stimulates the adrenal cortex to produce cortisol. Excess leads to Cushing’s syndrome (moon face, buffalo hump), not bony enlargement. * **TRH (B):** A hypothalamic hormone that stimulates the release of TSH and Prolactin. It does not mediate bone or soft tissue growth. * **TGF-beta (D):** A cytokine involved in cell growth, differentiation, and development, but it is not the mediator of GH-induced systemic growth in Acromegaly. **High-Yield Clinical Pearls for NEET-PG:** * **Screening Test:** Serum IGF-1 levels (Somatomedin C). * **Confirmatory Test:** Oral Glucose Tolerance Test (OGTT) with GH measurement [3]. Failure to suppress GH <1 ng/mL after 75g glucose is diagnostic. * **Most Common Cause:** Somatotroph adenoma of the anterior pituitary. * **Radiology:** Look for "spade-like" phalanges on X-ray and enlargement of the sella turcica on MRI. * **Treatment of Choice:** Transsphenoidal surgery [3]. Medical management includes Somatostatin analogues (Octreotide).

Q: Which of the following glucose transporters is insulin-dependent for its action?

GLUT 4. **Explanation:** The correct answer is **GLUT 4**. Glucose transporters (GLUTs) are membrane proteins that facilitate the transport of glucose across cell membranes via facilitated diffusion. **GLUT 4** is the only major glucose transporter that is **insulin-dependent**. In the resting state, GLUT 4 is sequestered in intracellular vesicles. When insulin binds to its receptor, it triggers a signaling cascade that causes these vesicles to translocation and fuse with the plasma membrane, allowing glucose entry into the cell. **Analysis of Options:** * **GLUT 1:** Found in RBCs, the blood-brain barrier, and the heart. It provides basal glucose uptake and is insulin-independent. * **GLUT 2:** A high-capacity, low-affinity transporter found in the Liver, Pancreatic beta cells, and the Basolateral membrane of the kidney/intestine. It acts as a "glucose sensor" and is insulin-independent. * **GLUT 3:** Found primarily in Neurons and the placenta. It has a high affinity for glucose, ensuring brain uptake even during hypoglycemia; it is insulin-independent. **High-Yield Clinical Pearls for NEET-PG:** * **Location of GLUT 4:** Primarily found in **Skeletal muscle** and **Adipose tissue**. * **Exercise:** Muscle contraction can also trigger GLUT 4 translocation to the membrane independent of insulin, which is why exercise helps manage blood sugar in Type 2 Diabetes. * **SGLT vs. GLUT:** Remember that SGLT (Sodium-Glucose Linked Transporters) use **secondary active transport** (found in the kidney and gut), whereas GLUTs use **facilitated diffusion**. * **GLUT 5:** Specifically transports **Fructose** (found in the small intestine and spermatozoa).

Q: Which hormone stimulates the synthesis of milk proteins?

Prolactin (PRL). **Explanation:** **Prolactin (PRL)** is the primary hormone responsible for the **synthesis of milk proteins** (such as casein and lactalbumin) and the initiation of lactation (lactogenesis). It is secreted by the lactotrophs of the anterior pituitary. During pregnancy, high levels of estrogen and progesterone stimulate breast development but inhibit the actual secretion of milk. Postpartum, the sudden drop in these steroid hormones allows Prolactin to stimulate the mammary alveolar cells to produce milk. **Analysis of Incorrect Options:** * **Luteinizing hormone (LH):** A gonadotropin that triggers ovulation in females and stimulates testosterone production by Leydig cells in males. It has no direct role in milk synthesis. * **Thyroid-stimulating hormone (TSH):** Regulates the production of thyroid hormones (T3 and T4) from the thyroid gland to control basal metabolic rate. * **Growth hormone (GH):** While structurally similar to Prolactin and possessing some lactogenic properties, its primary role is promoting linear growth and protein synthesis via IGF-1. **High-Yield NEET-PG Pearls:** * **Dopamine** (Prolactin-Inhibiting Hormone) is the primary physiological regulator that keeps Prolactin levels low in non-pregnant individuals. * **Oxytocin** is responsible for the **milk-ejection reflex** (let-down reflex) via contraction of myoepithelial cells, whereas Prolactin is for **milk production**. * **Suckling** is the strongest stimulus for both Prolactin and Oxytocin release. * **Hyperprolactinemia** often presents with galactorrhea and secondary amenorrhea (due to inhibition of GnRH).

Q: A 45-year-old female patient, known diabetic on insulin therapy, presents for a routine general checkup. On examination, truncal obesity is noted. The sensitivity of the agent used in the treatment of this patient is enhanced by which of the following?

Adiponectin. The patient described is a diabetic on **insulin therapy**. The question asks which factor enhances the sensitivity of insulin. **1. Why Adiponectin is Correct:** Adiponectin is an adipokine secreted by adipose tissue [2]. It acts as a potent **insulin sensitizer**. It enhances insulin sensitivity by [1]: * Increasing fatty acid oxidation via activation of **AMP-activated protein kinase (AMPK)** in skeletal muscle and the liver. * Decreasing hepatic gluconeogenesis. * Increasing glucose uptake in muscles. In patients with truncal obesity (as seen in this case), adiponectin levels are typically **decreased**, contributing to insulin resistance [1]. Therefore, higher levels of adiponectin directly enhance the sensitivity of the insulin the patient is receiving. **2. Why Other Options are Incorrect:** * **Leptin:** While also an adipokine, its primary role is regulating energy balance and appetite (satiety signal) [2]. In obesity, "leptin resistance" occurs. It does not directly enhance insulin sensitivity in the same potent manner as adiponectin. * **Glucagon:** This is a counter-regulatory hormone. It opposes insulin action by promoting glycogenolysis and gluconeogenesis, thereby **decreasing** insulin effectiveness and raising blood glucose. * **Insulin:** Insulin does not enhance its own sensitivity; chronic high levels of insulin (hyperinflation) actually lead to the downregulation of receptors and **increased** insulin resistance. **Clinical Pearls for NEET-PG:** * **Adiponectin Paradox:** Unlike other adipokines (like Resistin or TNF-α), adiponectin levels are **inversely** correlated with body fat percentage (lower in obesity). * **Thiazolidinediones (TZDs):** Drugs like Pioglitazone work partly by increasing the expression and secretion of adiponectin. * **AMPK Activation:** This is the common pathway for both Adiponectin and Metformin to improve insulin sensitivity.

Q: Which of the following is NOT a physiologic change of thyroid metabolism during pregnancy?

TSH level is highest during the first trimester. **Explanation:** The correct answer is **D**. During pregnancy, thyroid physiology undergoes significant changes driven by rising levels of **Human Chorionic Gonadotropin (hCG)** and **Estrogen**. 1. **Why Option D is the correct (incorrect statement):** hCG shares a common alpha-subunit with TSH and can directly stimulate the TSH receptor. During the **first trimester**, hCG levels peak, leading to a transient increase in free T4. This rise in T4 exerts negative feedback on the pituitary, causing **TSH levels to reach their lowest point** (nadir) during the first trimester, not the highest. 2. **Why the other options are wrong (correct physiologic changes):** * **Option B:** High estrogen levels stimulate the liver to increase the synthesis of **Thyroxine-Binding Globulin (TBG)** and decrease its clearance. * **Option A:** Because TBG levels are elevated, more T4 and T3 are bound. To maintain a constant level of "free" (active) hormone, the total pool of thyroid hormones increases. Thus, **Total T4 and T3 are elevated**, while Free T4/T3 remain largely within normal limits. * **Option C:** hCG is a structural analog of TSH. At high concentrations (especially weeks 8–12), it acts as a weak thyrotropin, stimulating the thyroid gland. **High-Yield Clinical Pearls for NEET-PG:** * **Total T4** in pregnancy is roughly **1.5 times** the non-pregnant value. * The **TSH reference range is lower** in pregnancy (Lower limit ~0.1 mIU/L; Upper limit ~2.5–3.0 mIU/L in the first trimester). * **Iodine requirements increase** during pregnancy due to increased glomerular filtration rate (renal loss) and fetal transfer. * **Thyroid size** may increase slightly (goitrogenesis) due to hCG stimulation and iodine deficiency, but significant goiter is always pathologic.

Question 1

The metabolic functions of insulin include all of the following except?

Accepted Answer

Increased lipoprotein lipase activity

Answer

Increased glycogen synthesis in the liver

Answer

Decreased hepatic gluconeogenesis

Answer

Increased transport of glucose into deep tissues

Question 2

Which of the following is NOT a stimulus for insulin secretion?

Accepted Answer

Hypokalemia

Answer

Glucagon

Answer

Ketone bodies

Answer

Amino acids

Question 3

What is the effect of cortisol?

Accepted Answer

Decreased bone matrix

Answer

Increased bone matrix

Answer

Increases lymphocytes

Answer

Increases RBCs

Question 4

Which of the following is NOT an effect of the T3 hormone?

Accepted Answer

It decreases pulse pressure

Answer

It increases the heart rate

Answer

It increases the stroke volume

Answer

It decreases the peripheral resistance

Question 5

A middle-aged man notices that he can no longer fit in his shoes and observes enlargement of his jaw and phalanges. Which hormone mediates these effects?

Accepted Answer

Somatomedin

Answer

Adrenocorticotropic hormone (ACTH)

Answer

Thyrotropin-releasing hormone (TRH)

Answer

Transforming growth factor beta (TGF-beta)

Question 6

Which of the following glucose transporters is insulin-dependent for its action?

Accepted Answer

GLUT 4

Answer

GLUT 1

Answer

GLUT 2

Answer

GLUT 3

Question 7

Which hormone stimulates the synthesis of milk proteins?

Accepted Answer

Prolactin (PRL)

Answer

Luteinizing hormone (LH)

Answer

Thyroid-stimulating hormone (TSH)

Answer

Growth hormone (GH)

Question 8

A diet deficient in calcium will result in what physiological change?

Accepted Answer

Production of parathyroid hormone and bone resorption

Answer

Stimulation of the thyroid gland

Answer

Increased ability to cross-link fibrin

Answer

Production of Calcitonin and a low blood calcium level

Question 9

A 45-year-old female patient, known diabetic on insulin therapy, presents for a routine general checkup. On examination, truncal obesity is noted. The sensitivity of the agent used in the treatment of this patient is enhanced by which of the following?

Accepted Answer

Adiponectin

Answer

Leptin

Answer

Glucagon

Answer

Insulin

Question 10

Which of the following is NOT a physiologic change of thyroid metabolism during pregnancy?

Accepted Answer

TSH level is highest during the first trimester

Answer

Increased levels of total T4 and T3

Answer

Elevated levels of serum TBG

Answer

hCG acts at the TSH receptor

Endocrinology — MCQs

Endocrinology — MCQs

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