Endocrinology Practice Questions

Q: A 30-year-old patient presents with symptoms of hyperthyroidism, including palpitations and heat intolerance. Which hormone is primarily responsible for these symptoms?

Triiodothyronine (T3). ***Triiodothyronine (T3)*** - **T3** is the **biologically active form** of thyroid hormone and is several times more potent than T4, directly mediating the effects of hyperthyroidism [1]. - Symptoms like **palpitations** and **heat intolerance** are direct consequences of increased metabolic rate and heightened adrenergic sensitivity driven by elevated T3 [3]. *Thyroxine (T4)* - **Thyroxine (T4)** is the primary hormone secreted by the thyroid gland, but it is largely a **prohormone** that must be converted to T3 to exert its full biological effects. - While elevated T4 is present in hyperthyroidism, the symptoms are primarily mediated by its conversion to T3 at the tissue level. *Thyroid-stimulating hormone (TSH)* - **TSH** is produced by the pituitary gland and *stimulates* the thyroid to produce T3 and T4; in primary hyperthyroidism, TSH levels are typically **suppressed** due to negative feedback [2]. - TSH itself does not directly cause the symptoms of hyperthyroidism but rather regulates the production of the hormones that do. *Parathyroid hormone (PTH)* - **PTH** is involved in **calcium and phosphate homeostasis** and is produced by the parathyroid glands. - It has no direct role in regulating metabolism or causing symptoms of thyroid dysfunction.

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

Cortisol. ***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.

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

Parathyroid hormone. ***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.

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

Glycogenolysis (breakdown of glycogen to release glucose). ***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**.

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

Decreased basal metabolic rate. ***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.

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

Aldosterone. **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.

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

Blood pressure. ***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.

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

10-15 mg/day. ***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.

Q: At what weeks of gestation is the fetal thyroid gland capable of synthesizing hormones?

10-12 weeks. ***10-12 weeks*** - The fetal thyroid gland begins to develop around **3-4 weeks of gestation** but becomes functionally mature enough to **synthesize hormones (thyroxine and triiodothyronine)** by 10-12 weeks. - At this stage, the fetal pituitary gland starts secreting **thyroid-stimulating hormone (TSH)**, which stimulates the fetal thyroid to produce and secrete its own hormones. *6-7 weeks* - While the **thyroid primordium** is forming and descending during this period, it is not yet capable of synthesizing significant amounts of hormones. - This stage is primarily characterized by the **morphological development** of the gland. *7-8 weeks* - The fetal thyroid gland continues to differentiate and grow during these weeks, but the **follicles are not yet fully developed or active** in hormone synthesis. - **Iodide trapping** begins around this time, which is a precursor to hormone synthesis. *12-14 weeks* - By this stage, the fetal thyroid is **actively synthesizing and secreting hormones**, and fetal thyroid function is well established. - However, the initial capability for synthesis begins slightly earlier, around **10-12 weeks**.

Q: Which hormone primarily regulates glucose levels and has indirect effects on ion concentrations in cells?

Insulin. ***Insulin*** - **Insulin** is the primary hormone responsible for regulating **blood glucose levels** by promoting glucose uptake into cells and stimulating **glycogenesis**. - Beyond glucose, insulin also promotes the uptake of **potassium** into cells, thus impacting ion concentrations. *GH* - **Growth hormone (GH)** primarily promotes **growth** and **protein synthesis** and has an **anti-insulin effect**, increasing blood glucose rather than lowering it. - While GH can influence electrolyte balance indirectly through growth and metabolic processes, it is not its primary regulatory function. *Thyroxine* - **Thyroxine (T4)** is a **thyroid hormone** that primarily regulates **metabolic rate**, influencing energy expenditure, heart rate, and body temperature. - While it affects overall cellular metabolism, it does not directly regulate glucose or ion concentrations in the same immediate way as insulin. *Estrogen* - **Estrogen** is a **sex hormone** primarily involved in the development and regulation of the **female reproductive system** and secondary sexual characteristics. - Although it can have broad metabolic effects, including some influence on glucose metabolism, it is not a primary regulator of blood glucose or ion concentrations.

Question 1

A 30-year-old patient presents with symptoms of hyperthyroidism, including palpitations and heat intolerance. Which hormone is primarily responsible for these symptoms?

Accepted Answer

Triiodothyronine (T3)

Answer

Thyroxine (T4)

Answer

Thyroid-stimulating hormone (TSH)

Answer

Parathyroid hormone (PTH)

Question 2

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

Accepted Answer

Cortisol

Answer

Insulin

Answer

Epinephrine

Answer

Aldosterone

Question 3

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

Accepted Answer

Parathyroid hormone

Answer

Calcitonin

Answer

Thyroxine

Answer

Aldosterone

Question 4

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

Accepted Answer

Glycogenolysis (breakdown of glycogen to release glucose)

Answer

Lipogenesis (conversion of glucose to fat)

Answer

Glycolysis (breakdown of glucose for energy)

Answer

Gluconeogenesis (synthesis of glucose from non-carbohydrate sources)

Question 5

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

Accepted Answer

Decreased basal metabolic rate

Answer

Increased basal metabolic rate

Answer

Increased serum cholesterol

Answer

Decreased protein synthesis

Question 6

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

Accepted Answer

Aldosterone

Answer

Cortisol

Answer

Testosterone

Answer

Estradiol

Question 7

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

Accepted Answer

Blood pressure

Answer

Potassium concentration

Answer

Blood glucose level

Answer

Sodium concentration

Question 8

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

Accepted Answer

10-15 mg/day

Answer

50-60 mg/day

Answer

30-40 mg/day

Answer

15-25 mg/day

Question 9

At what weeks of gestation is the fetal thyroid gland capable of synthesizing hormones?

Accepted Answer

10-12 weeks

Answer

6-7 weeks

Answer

7-8 weeks

Answer

12-14 weeks

Question 10

Which hormone primarily regulates glucose levels and has indirect effects on ion concentrations in cells?

Accepted Answer

Insulin

Answer

GH

Answer

Thyroxine

Answer

Estrogen

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?