Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 771: What is the primary effect of thyroid hormones on the metabolic rate?

A. Decrease metabolic rate
B. Increase metabolic rate (Correct Answer)
C. No effect on metabolic rate
D. Variable effects on metabolic rate

Explanation: ***Increase metabolic rate*** - Thyroid hormones **triiodothyronine (T3)** and **thyroxine (T4)** primarily act to increase the body's overall **basal metabolic rate**. - They enhance cellular oxygen consumption and stimulate various metabolic pathways, leading to increased **energy production**. *Decrease metabolic rate* - A decrease in metabolic rate is characteristic of conditions like **hypothyroidism**, where there is insufficient thyroid hormone production. - This typically results in symptoms such as **fatigue**, weight gain, and cold intolerance. *No effect on metabolic rate* - This option is incorrect because thyroid hormones are **fundamental regulators** of metabolism, directly influencing cellular functions across almost all tissues. - Their presence or absence has a profound and measurable impact on the body's **energy expenditure**. *Variable effects on metabolic rate* - While the *degree* of metabolic increase can vary with hormone levels, the *primary effect* of thyroid hormones is consistently to elevate metabolism. - The direct and overarching action is **stimulatory**, not variably increasing or decreasing depending on minor contextual factors.

Question 772: Which of the following is most likely to increase in response to chronic stress?

A. Insulin
B. Cortisol (Correct Answer)
C. Epinephrine
D. Aldosterone

Explanation: ***Cortisol*** - **Cortisol** is a primary **stress hormone** released by the adrenal glands in response to activation of the **hypothalamic-pituitary-adrenal (HPA) axis** during chronic stress. - Its continuous elevation can lead to various health problems, including **immune suppression**, **weight gain**, and **cognitive impairment**. *Insulin* - While stress can acutely increase **blood glucose** levels, indirectly affecting insulin, insulin itself is not typically elevated long-term by chronic stress directly. - **Insulin** primarily regulates glucose metabolism and is more directly influenced by dietary intake and insulin sensitivity. *Epinephrine* - **Epinephrine** (**adrenaline**) is strongly elevated during **acute stress** (fight-or-flight response), but chronic stress generally involves a more sustained increase in cortisol rather than epinephrine. - Its effects are rapid and short-lived, primarily preparing the body for immediate action. *Aldosterone* - **Aldosterone** is mainly involved in regulating **blood pressure** and **electrolyte balance** through the **renin-angiotensin-aldosterone system (RAAS)**. - While indirect effects on the RAAS can occur during stress, aldosterone is not typically the primary hormone that shows a sustained increase in response to chronic psychological stress.

Question 773: Which of the following hormones is secreted in response to low blood calcium levels?

A. Calcitonin
B. Parathyroid hormone (Correct Answer)
C. Thyroxine
D. Aldosterone

Explanation: ***Parathyroid hormone*** - **Parathyroid hormone (PTH)** is the primary hormone responsible for increasing blood calcium levels in response to **hypocalcemia**. - It acts on bone to resorb calcium, on the kidneys to reabsorb calcium and excrete phosphate, and stimulates the production of **calcitriol** (active vitamin D) to enhance intestinal calcium absorption. *Calcitonin* - **Calcitonin** is secreted by the **C-cells of the thyroid gland** and acts to **lower blood calcium levels** by inhibiting osteoclast activity and promoting calcium excretion by the kidneys. - It is released in response to **high blood calcium levels**, not low. *Thyroxine* - **Thyroxine (T4)** is a thyroid hormone that primarily regulates **metabolism**, growth, and development. - It does not have a direct or significant role in the regulation of blood calcium levels. *Aldosterone* - **Aldosterone** is a mineralocorticoid steroid hormone produced by the **adrenal cortex** that primarily regulates **sodium and potassium balance** and blood pressure. - It does not play a role in regulating blood calcium levels.

Question 774: What is the main function of the hormone parathyroid hormone (PTH)?

A. Increase blood calcium levels (Correct Answer)
B. Decrease blood calcium levels
C. Stimulate insulin release
D. Decrease glucose levels

Explanation: ***Increase blood calcium levels*** - **Parathyroid hormone (PTH)** is the primary regulator of **calcium homeostasis**, acting to raise circulating calcium. - It achieves this by promoting **bone resorption**, increasing **renal reabsorption of calcium**, and enhancing **vitamin D activation** to increase intestinal calcium absorption. *Decrease blood calcium levels* - This is the main function of **calcitonin**, a hormone produced by the parafollicular cells of the thyroid gland, not PTH. - Calcitonin primarily acts to inhibit osteoclast activity and promote renal calcium excretion, thus lowering blood calcium. *Stimulate insulin release* - This is the primary function of **glucose**, which stimulates **beta cells** in the pancreas to release insulin, and of certain gastrointestinal hormones. - PTH has no direct role in regulating insulin secretion. *Decrease glucose levels* - This is the main action of **insulin**, which facilitates glucose uptake by cells and promotes glycogen synthesis in the liver and muscles. - PTH is not involved in glucose metabolism or the regulation of blood glucose concentrations.

Question 775: A patient with untreated hypothyroidism will exhibit which of the following as the PRIMARY metabolic change affecting energy expenditure?

A. Increased basal metabolic rate
B. Decreased basal metabolic rate (Correct Answer)
C. Increased serum cholesterol
D. Decreased protein synthesis

Explanation: ***Decreased basal metabolic rate*** - **Thyroid hormones** (T3 and T4) are the primary regulators of **basal metabolic rate (BMR)**, which represents the body's baseline energy expenditure. - In hypothyroidism, reduced thyroid hormone levels lead to **decreased oxygen consumption** and **reduced heat production** in tissues, resulting in a fundamentally lower metabolic rate. - This is the **most direct and primary metabolic change**, manifesting as **fatigue**, **weight gain**, **cold intolerance**, and **bradycardia**. *Increased basal metabolic rate* - This is characteristic of **hyperthyroidism**, not hypothyroidism. - Excess thyroid hormones increase cellular metabolism, causing **weight loss**, **heat intolerance**, and **tachycardia**. *Increased serum cholesterol* - This is indeed seen in hypothyroidism due to **decreased LDL receptor expression** and **reduced hepatic clearance** of cholesterol. - However, this is a **secondary consequence** of the decreased metabolic rate, not the primary change in energy metabolism itself. - Hypercholesterolemia develops as a result of slowed lipid metabolism. *Decreased protein synthesis* - Thyroid hormones do stimulate protein synthesis, and hypothyroidism causes **reduced protein turnover**. - However, the **most fundamental metabolic change** is the reduction in overall energy expenditure (BMR), which encompasses multiple metabolic pathways including protein, lipid, and carbohydrate metabolism. - Decreased BMR is the primary defect from which other metabolic changes follow.

Question 776: What metabolic pathway is primarily activated during the fight or flight response?

A. Lipogenesis (conversion of glucose to fat)
B. Glycogenolysis (breakdown of glycogen to release glucose) (Correct Answer)
C. Glycolysis (breakdown of glucose for energy)
D. Gluconeogenesis (synthesis of glucose from non-carbohydrate sources)

Explanation: ***Glycogenolysis (breakdown of glycogen to release glucose)*** - During the **fight-or-flight response**, the body needs a rapid supply of glucose for immediate energy to fuel muscle activity and brain function. - **Glycogenolysis** is the **primary rate-limiting pathway** activated by catecholamines (epinephrine and norepinephrine), which rapidly breaks down stored **glycogen** in the liver and muscles into glucose. - This provides the immediate substrate availability that distinguishes the acute stress response. *Lipogenesis (conversion of glucose to fat)* - **Lipogenesis** is the process of synthesizing **fat** from excess glucose, primarily for long-term energy storage. - This anabolic process is activated during periods of caloric surplus and is **suppressed** during the fight-or-flight response. *Glycolysis (breakdown of glucose for energy)* - While **glycolysis** is indeed activated during fight-or-flight to metabolize the glucose released, it is not the **primary** pathway that defines this response. - Glycolysis depends on substrate availability; the **primary activation** is at the level of glucose mobilization through glycogenolysis. - Without glycogenolysis first providing glucose, glycolysis cannot meet the increased energy demands. *Gluconeogenesis (synthesis of glucose from non-carbohydrate sources)* - **Gluconeogenesis** synthesizes glucose from non-carbohydrate precursors like amino acids and glycerol, and it is a slower, more sustained process. - It is crucial for maintaining blood glucose during prolonged fasting or chronic stress, but it is **not fast enough** to meet the immediate energy demands of the acute **fight-or-flight response**.

Question 777: Which hormone, derived from cholesterol, plays a vital role in regulating sodium and water balance in the body?

A. Cortisol
B. Aldosterone (Correct Answer)
C. Testosterone
D. Estradiol

Explanation: **Aldosterone** - Aldosterone is a **mineralocorticoid** hormone synthesized from **cholesterol** in the adrenal cortex. - Its primary function is to regulate **sodium and water balance** by promoting sodium reabsorption and potassium excretion in the renal tubules, thereby influencing blood pressure. *Cortisol* - Cortisol is a **glucocorticoid** hormone, also synthesized from cholesterol, primarily involved in **stress response**, metabolism, and immune function. - While it can have some mineralocorticoid activity, its main role is not the direct regulation of sodium and water balance at physiological concentrations. *Testosterone* - Testosterone is an **androgen** (sex hormone) derived from cholesterol, predominantly produced by the testes in males and adrenal glands in both sexes. - Its main functions include the development of male secondary sexual characteristics, muscle mass, and bone density, not sodium and water balance. *Estradiol* - Estradiol is an **estrogen** (sex hormone) derived from cholesterol, primarily produced by the ovaries in females. - It plays a crucial role in the female reproductive cycle, bone health, and cardiovascular function, with no direct primary role in sodium and water balance.

Question 778: A decrease in which of the following physiological parameters would stimulate the release of aldosterone from the adrenal cortex?

A. Potassium concentration
B. Blood glucose level
C. Blood pressure (Correct Answer)
D. Sodium concentration

Explanation: ***Blood pressure*** - A decrease in **blood pressure** (or blood volume) is sensed by the **juxtaglomerular apparatus** in the kidneys, leading to the release of renin. - Renin initiates the **renin-angiotensin-aldosterone system (RAAS)**, ultimately stimulating aldosterone secretion to increase **sodium** and water retention. *Sodium concentration* - While aldosterone's primary role is to promote **sodium reabsorption**, a *decrease* in sodium concentration itself doesn't directly stimulate aldosterone release. - Instead, reduced sodium (and thus reduced osmolality) can indirectly affect blood volume, which then triggers the RAAS. *Potassium concentration* - An *increase* in **potassium concentration** (hyperkalemia) is a direct stimulus for aldosterone release, as aldosterone promotes potassium excretion. - A *decrease* in potassium concentration would **inhibit** aldosterone release, not stimulate it. *Blood glucose level* - **Blood glucose level** primarily regulates the release of insulin and glucagon from the pancreas. - It has no direct or significant role in stimulating aldosterone secretion from the adrenal cortex.

Question 779: What is the normal daily production rate of cortisol in adults?

A. 50-60 mg/day
B. 10-15 mg/day (Correct Answer)
C. 30-40 mg/day
D. 15-25 mg/day

Explanation: ***10-15 mg/day*** - The **normal physiological production** of cortisol in a healthy adult is typically **10-20 mg per day**, making 10-15 mg/day the most accurate answer representing basal cortisol secretion. - This production rate is crucial for maintaining various **homeostatic functions**, including stress response, metabolism, immune regulation, and circadian rhythm. - This range aligns with standard physiology textbooks (Ganong, Guyton & Hall) and represents unstressed, baseline adrenal function. *15-25 mg/day* - This range represents the **upper end of normal to slightly elevated** cortisol production, often seen during moderate physiological stress or increased activity. - While still within acceptable limits, it exceeds the typical basal production rate of 10-20 mg/day cited in most physiology references. - This might be observed in individuals under moderate stress or with slightly increased adrenal activity. *30-40 mg/day* - This production rate indicates **significantly increased cortisol secretion**, typically seen during substantial stress, acute illness, surgery, or pathological conditions like Cushing's syndrome. - It substantially exceeds the normal physiological range for basal cortisol production in a healthy, unstressed individual. *50-60 mg/day* - This level of cortisol production is **markedly elevated** and is usually observed in states of severe stress, critical illness, major surgery, or pathological hypercortisolism. - It is far above the normal daily production rate and would warrant clinical investigation if sustained.

Question 780: What hormone is primarily responsible for triggering the LH surge?

A. Estrogen (Correct Answer)
B. Anti-Mullerian Hormone (AMH)
C. Follicle-Stimulating Hormone (FSH)
D. Progesterone

Explanation: ***Estrogen*** - As the dominant follicle matures, it produces increasing amounts of **estrogen**, primarily **estradiol**. - When **estradiol** levels reach a critical threshold, it switches from negative to positive feedback on the hypothalamus and anterior pituitary, leading to the **LH surge**. *Anti-Mullerian Hormone (AMH)* - **AMH** is produced by granulosa cells of small antral follicles and is a marker of **ovarian reserve**. - It plays a role in regulating follicular development but is not directly responsible for initiating the **LH surge**. *Follicle-Stimulating Hormone (FSH)* - **FSH** stimulates the growth and development of ovarian follicles, which in turn produce estrogen. - While essential for follicular development, the surge is not triggered by FSH itself but rather by the high **estrogen** levels resulting from FSH action. *Progesterone* - **Progesterone** levels rise significantly **after** the LH surge and ovulation, primarily from the corpus luteum, to prepare the uterus for implantation. - It acts to inhibit further LH and FSH release and is not the primary trigger for the initial **LH surge**.

Practice by Chapter

Principles of Endocrine Regulation

Practice Questions

Hypothalamus and Pituitary Gland

Practice Questions

Thyroid Physiology

Practice Questions

Adrenal Cortex and Medulla

Practice Questions

Pancreatic Hormones and Glucose Metabolism

Practice Questions

Calcium and Phosphate Homeostasis

Practice Questions

Growth Hormone and Growth Factors

Practice Questions

Endocrine Regulation of Metabolism

Practice Questions

Hormone Receptors and Signaling

Practice Questions

Assessment of Endocrine Function

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free