Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 761: What is the role of leptin in energy homeostasis, and what are the current evidence-based therapeutic approaches for managing leptin resistance in obesity?

A. Leptin decreases appetite, use bariatric surgery for severe obesity
B. Leptin increases appetite, use GLP-1 receptor agonists
C. Leptin increases appetite, use lifestyle modifications and caloric restriction
D. Leptin decreases appetite, use lifestyle modifications and evidence-based pharmacotherapy (Correct Answer)

Explanation: ***Leptin decreases appetite, use lifestyle modifications and evidence-based pharmacotherapy*** - **Leptin** is an adipocyte-derived hormone that signals **satiety** to the hypothalamus, leading to **decreased appetite** and increased energy expenditure. - In common obesity, **leptin resistance** develops where high leptin levels fail to suppress appetite due to impaired signaling. - **First-line management of leptin resistance** includes **lifestyle modifications** (weight loss improves leptin sensitivity), **dietary interventions**, and **evidence-based pharmacotherapy** such as metformin (improves insulin sensitivity), GLP-1 receptor agonists, and addressing underlying inflammation. - This represents the **standard, evidence-based approach** for managing leptin resistance in obesity. *Leptin decreases appetite, use bariatric surgery for severe obesity* - While this correctly identifies leptin's role in **decreasing appetite**, bariatric surgery is reserved for **severe/morbid obesity** (BMI >40 or >35 with comorbidities) and is a **last-resort intervention**, not a first-line treatment for leptin resistance. - The question specifically asks about managing **leptin resistance**, where lifestyle and pharmacotherapy are the primary evidence-based approaches. *Leptin increases appetite, use GLP-1 receptor agonists* - This is incorrect because **leptin's primary physiological role is to decrease appetite**, not increase it. - Although **GLP-1 receptor agonists** are effective pharmacological treatments that can help with obesity and may improve leptin sensitivity, the fundamental misrepresentation of leptin's function makes this option incorrect. *Leptin increases appetite, use lifestyle modifications and caloric restriction* - This option incorrectly states that **leptin increases appetite**; its actual role is to **suppress appetite** and signal energy sufficiency. - While **lifestyle modifications and caloric restriction** are crucial components of obesity management, the incorrect premise about leptin's physiological function invalidates this option.

Question 762: Which gland is primarily responsible for regulating metabolism through the secretion of hormones?

A. Pituitary gland
B. Thyroid gland (Correct Answer)
C. Adrenal gland
D. Pancreas

Explanation: ***Correct Option: Thyroid gland*** - The **thyroid gland** produces **thyroid hormones (T3 and T4)**, which are crucial regulators of the body's metabolic rate, influencing energy production, protein synthesis, and body temperature. - **Dysfunction** of the thyroid gland, such as in **hypothyroidism** or **hyperthyroidism**, directly impacts an individual's metabolic state. *Incorrect: Pituitary gland* - The **pituitary gland** is often called the "master gland" because it controls other endocrine glands, but it regulates metabolism indirectly by **secreting TSH**, which stimulates the thyroid gland. - Its direct hormonal contributions are more focused on growth, reproduction, and stress response, rather than primary metabolic regulation. *Incorrect: Adrenal gland* - The **adrenal glands** primarily produce hormones like **cortisol** and **adrenaline**, which are involved in stress response, blood pressure regulation, and electrolyte balance. - While cortisol does influence glucose metabolism, the adrenal glands are not the primary regulators of overall metabolic rate. *Incorrect: Pancreas* - The **pancreas** is vital for regulating **blood glucose levels** through the secretion of **insulin and glucagon**. - While this is a critical aspect of metabolism, its primary role is glucose homeostasis, not the overall metabolic rate like the thyroid.

Question 763: The primary action of parathyroid hormone (PTH) is to:

A. Increase blood calcium levels (Correct Answer)
B. Decrease blood phosphate levels
C. Decrease blood potassium levels
D. Increase blood sodium levels

Explanation: ***Increase blood calcium levels*** - **Parathyroid hormone (PTH)** is the primary regulator of **calcium homeostasis**, acting to raise serum calcium when levels are low. - It achieves this by promoting **calcium reabsorption in the kidneys**, stimulating **osteoclast activity** to release calcium from bone, and indirectly increasing **intestinal calcium absorption** via vitamin D activation. *Decrease blood phosphate levels* - While PTH does decrease blood phosphate levels, this is a **secondary effect** to its primary goal of increasing calcium. - PTH achieves this by **reducing phosphate reabsorption** in the renal tubules, a mechanism that helps prevent calcium-phosphate precipitation as calcium levels rise. *Decrease blood potassium levels* - **PTH** has no direct or significant role in regulating **blood potassium levels**. - **Potassium balance** is primarily regulated by **aldosterone** and kidney function. *Increase blood sodium levels* - **PTH** does not directly influence **blood sodium levels**. - **Sodium balance** is predominantly controlled by the **renin-angiotensin-aldosterone system (RAAS)** and **antidiuretic hormone (ADH)**.

Question 764: In a patient with type 1 diabetes mellitus, which abnormal physiological process most directly contributes to hyperglycemia?

A. Decreased glucose uptake by cells
B. Decreased glycogen synthesis
C. Normal insulin sensitivity
D. Increased hepatic glucose production (Correct Answer)

Explanation: ***Increased hepatic glucose production*** - In **Type 1 Diabetes Mellitus (T1DM)**, the absolute deficiency of **insulin** removes its suppressive effect on the liver, leading to uncontrolled **gluconeogenesis** and **glycogenolysis**. - This persistent release of glucose from the liver into the bloodstream is the **most direct and primary contributor** to the **hyperglycemia** observed in T1DM patients. - The liver's continuous overproduction of glucose occurs even in the fasting state, which is a hallmark of diabetic hyperglycemia. *Decreased glucose uptake by cells* - While **decreased glucose uptake** by **insulin-sensitive cells** (like muscle and adipose tissue) does occur in T1DM due to insulin deficiency, it contributes more to the inability to lower blood glucose after meals. - This is a secondary contributor to hyperglycemia, as the liver's glucose overproduction is the more dominant and continuous process. *Decreased glycogen synthesis* - **Insulin** normally promotes **glycogen synthesis** in the liver and muscles. In T1DM, the lack of insulin does lead to decreased glycogen synthesis. - However, the inability to store glucose is less impactful on hyperglycemia than the liver's active overproduction and release of glucose through gluconeogenesis and glycogenolysis. *Normal insulin sensitivity* - **Insulin sensitivity** is generally **normal** in individuals with newly diagnosed **type 1 diabetes mellitus**. - The core problem is the absolute **deficiency of insulin**, not insulin resistance at the cellular level, which is characteristic of type 2 diabetes. - This option does not describe an abnormal process.

Question 765: Which hormone is primarily involved in the regulation of blood calcium levels?

A. Insulin
B. Cortisol
C. Parathyroid hormone (Correct Answer)
D. Thyroxine

Explanation: ***Parathyroid hormone*** - **Parathyroid hormone (PTH)** directly regulates blood calcium by increasing its reabsorption in the kidneys, stimulating calcium release from bones, and increasing intestinal calcium absorption via **vitamin D activation**. - It plays a crucial role in maintaining **calcium homeostasis** and preventing hypocalcemia. *Insulin* - **Insulin** is primarily involved in regulating **blood glucose levels** by promoting glucose uptake into cells and conversion to glycogen. - It has no direct primary role in the regulation of blood calcium levels. *Cortisol* - **Cortisol** is a **glucocorticoid** that primarily influences stress response, metabolism, and immune function, but not the primary regulation of blood calcium. - High levels of cortisol can indirectly affect calcium by increasing bone resorption, but it is not its primary function. *Thyroxine* - **Thyroxine (T4)** is a **thyroid hormone** that regulates metabolism, growth, and development. - Its primary role is not in the direct regulation of blood calcium levels.

Question 766: A patient is observed to have high levels of cortisol. What effect on carbohydrate metabolism is most likely?

A. Increased insulin sensitivity
B. Decreased gluconeogenesis
C. Increased glucose uptake by cells
D. Increased gluconeogenesis (Correct Answer)

Explanation: ***Increased gluconeogenesis*** - **Cortisol**, a glucocorticoid, promotes **gluconeogenesis** in the liver, which is the synthesis of glucose from non-carbohydrate precursors like amino acids and glycerol. - This action helps to **raise blood glucose levels**, preparing the body for "fight or flight" responses or periods of stress. *Increased insulin sensitivity* - High levels of cortisol actually *decrease* **insulin sensitivity** in peripheral tissues, leading to **insulin resistance**. - This effect contributes to **elevated blood glucose levels** by making cells less responsive to insulin's actions. *Decreased gluconeogenesis* - Cortisol's primary action on glucose metabolism is to *increase* **gluconeogenesis**, not decrease it. - A decrease in gluconeogenesis would typically lead to **lower blood glucose levels**, contradicting the known effects of elevated cortisol. *Increased glucose uptake by cells* - Cortisol generally *reduces* **glucose uptake by peripheral cells**, particularly in muscle and adipose tissue. - This mechanism, along with increased gluconeogenesis, contributes to the **hyperglycemic** effects of cortisol.

Question 767: Which hormone is responsible for the letdown reflex during breastfeeding?

A. Prolactin
B. Oxytocin (Correct Answer)
C. Estrogen
D. Progesterone

Explanation: **Oxytocin** - **Oxytocin** is released in response to suckling, causing **myoepithelial cells** around the alveoli in the breast to contract. - This contraction pushes milk from the alveoli through the ducts, leading to the **milk ejection reflex**, commonly known as the **letdown reflex**. *Prolactin* - **Prolactin** is primarily responsible for the **production of milk** (lactogenesis) by the mammary glands. - While essential for lactation, it does not directly cause the *ejection* or letdown of milk. *Estrogen* - **Estrogen** plays a significant role in the **development of mammary glands** during puberty and pregnancy. - However, high levels of estrogen can **inhibit milk production** post-delivery and are not involved in the letdown reflex. *Progesterone* - **Progesterone** is crucial for the development of ductal and lobular structures in the breast during pregnancy. - Similar to estrogen, high levels of progesterone **inhibit lactation** postpartum and it does not play a direct role in the letdown reflex.

Question 768: What is the primary function of the enzyme renin in the renin-angiotensin-aldosterone system?

A. Convert angiotensinogen to angiotensin I (Correct Answer)
B. Convert angiotensin I to angiotensin II
C. Increase blood potassium levels
D. Decrease blood pressure

Explanation: ***Convert angiotensinogen to angiotensin I*** - Renin is an **enzyme** released by the **juxtaglomerular cells** in the kidneys in response to decreased blood pressure, decreased sodium delivery to the distal tubule, or sympathetic stimulation. - Its primary role is to cleave **angiotensinogen**, a protein produced by the liver, into **angiotensin I**. *Convert angiotensin I to angiotensin II* - This conversion is primarily carried out by **Angiotensin-Converting Enzyme (ACE)**, which is found predominantly in the endothelial cells of the lungs. - **Angiotensin II** is the main active hormone in the RAAS, responsible for vasoconstriction, aldosterone release, and ADH secretion. *Increase blood potassium levels* - This is incorrect; **aldosterone**, a hormone whose secretion is stimulated by angiotensin II, actually promotes **potassium excretion** in the kidneys. - The primary function of the RAAS is to increase blood pressure and volume, not directly regulate potassium homeostasis. *Decrease blood pressure* - This is incorrect; the entire purpose of the **renin-angiotensin-aldosterone system (RAAS)** is to **increase blood pressure** and blood volume. - Renin initiates a cascade that ultimately leads to vasoconstriction, increased water and sodium retention, all of which elevate blood pressure.

Question 769: What is the primary action of thyroid-stimulating hormone (TSH) on the function of the thyroid gland?

A. Decrease iodine uptake
B. Increase calcitonin release
C. Stimulate thyroxine synthesis (Correct Answer)
D. Inhibit hormone release

Explanation: ***Stimulate thyroxine synthesis*** - **TSH** binds to receptors on thyroid follicular cells, leading to a cascade of events that **stimulate the synthesis and release of thyroid hormones**, primarily **thyroxine (T4)**. - This action is crucial for maintaining proper **metabolic rate, growth, and development**. *Decrease iodine uptake* - **TSH** primarily **increases iodine uptake** by the thyroid follicular cells, which is a necessary step for the synthesis of thyroid hormones. - Decreased iodine uptake would lead to reduced thyroid hormone production, which is contrary to TSH's stimulatory role. *Increase calcitonin release* - **Calcitonin** is produced by the **parafollicular C cells** of the thyroid gland, not the follicular cells that are the primary target of TSH. - The primary stimulus for calcitonin release is **hypercalcemia**, not TSH. *Inhibit hormone release* - **TSH** has a **stimulatory effect** on the thyroid gland, promoting both the synthesis and release of thyroid hormones. - Inhibition of hormone release would negate the physiological role of TSH in regulating thyroid function.

Question 770: Which of the following hormones is most likely to increase during dehydration?

A. ADH (Correct Answer)
B. Aldosterone
C. ANP
D. Cortisol

Explanation: ***ADH*** - Dehydration leads to increased **plasma osmolality**, which is the primary stimulus for **ADH (vasopressin)** secretion from the posterior pituitary. - ADH acts on the **collecting ducts** of the kidneys to increase water reabsorption, concentrating urine and conserving body water. *Aldosterone* - While dehydration can indirectly stimulate **aldosterone** release via the **renin-angiotensin-aldosterone system** (due to decreased blood volume/pressure), its primary role is in **sodium reabsorption** and **potassium excretion**. - ADH is more directly and acutely responsive to changes in **plasma osmolality** which is a hallmark of dehydration. *ANP* - **Atrial natriuretic peptide (ANP)** is released in response to **atrial stretch** caused by **increased blood volume** or pressure. - Dehydration typically leads to **decreased blood volume** and pressure, thus ANP levels would likely decrease, or at least not increase significantly. *Cortisol* - **Cortisol** is a stress hormone released in response to various physical and physiological stressors, and it has some roles in fluid balance by influencing ADH. - However, it is not the **primary or most direct hormonal response** to dehydration for fluid conservation; ADH plays that crucial role.

Practice by Chapter

Principles of Endocrine Regulation

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Hypothalamus and Pituitary Gland

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Thyroid Physiology

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Adrenal Cortex and Medulla

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Pancreatic Hormones and Glucose Metabolism

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Calcium and Phosphate Homeostasis

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Growth Hormone and Growth Factors

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Endocrine Regulation of Metabolism

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Hormone Receptors and Signaling

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Assessment of Endocrine Function

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