Endocrinology Practice Questions

Q: Serum prolactin levels are highest

During third trimester of pregnancy. ***Correct: During third trimester of pregnancy*** - **Serum prolactin levels reach their absolute highest** during the **third trimester of pregnancy**, rising progressively from normal levels (5-25 ng/mL) to peak values of **200-400 ng/mL** near term. - This represents the **highest physiological prolactin levels** observed in humans. - Despite these high levels, **lactation does not occur** during pregnancy because **estrogen and progesterone** block prolactin's action on mammary tissue. - The high prolactin prepares the breast for lactation but milk secretion is inhibited until delivery. *Incorrect: 24 hrs after parturition* - After delivery, prolactin levels actually begin to **decline** from their pregnancy peak, though they remain elevated (around 200 ng/mL). - While **lactogenesis II** (copious milk production) begins 24-72 hours postpartum, this is due to the **removal of estrogen/progesterone inhibition**, not because prolactin levels peak at this time. - The confusion arises from conflating **functional milk production** with **peak hormone levels**. *Incorrect: REM sleep* - Prolactin exhibits **circadian variation** with nocturnal rise during sleep, peaking in early morning hours. - However, these sleep-related peaks (typically 25-40 ng/mL) are **much lower** than pregnancy levels. - This physiological variation is unrelated to reproductive function. *Incorrect: In actively lactating mothers* - During established lactation, basal prolactin levels gradually decline over weeks to months. - Each **suckling episode** causes transient prolactin surges (2-10 fold increase), but these peaks are still **lower than third trimester levels**. - By 6 months postpartum, basal prolactin may return near pre-pregnancy levels despite continued lactation.

Q: In females, the adrenal glands are the exclusive source for secretion of?

DHEAS. ***DHEAS*** - **Dehydroepiandrosterone sulfate (DHEAS)** is almost exclusively produced by the **adrenal glands** in both males and females. - Its levels are often used as a marker of **adrenal androgen production**, making it unique in terms of its exclusive adrenal source in women. *Testosterone* - While the adrenal glands produce small amounts of androgens, the primary source of **testosterone** in females is the **ovaries** and peripheral conversion of adrenal precursors. - Testes are the primary source in males, and it is not exclusively from the adrenal glands in females. *Estrogen* - **Estrogen** is primarily produced by the **ovaries** in females, particularly estradiol. - Peripheral conversion of androgens in adipose tissue also contributes to estrogen levels, and the adrenal glands do not secrete significant amounts directly. *Progesterone* - **Progesterone** is predominantly produced by the **corpus luteum** in the ovary after ovulation and by the placenta during pregnancy. - The adrenal glands produce only minor amounts of progesterone.

Q: What effect does insulin have on GLUT4 receptors in muscle cells?

Promotes their translocation to cell membrane. ***Promotes their translocation to cell membrane*** - Insulin **stimulates the movement of GLUT4 vesicles** from the intracellular compartment to the plasma membrane. - This translocation increases the number of **GLUT4 transporters** on the cell surface, facilitating glucose uptake. *Inhibits their activity* - Insulin does not inhibit the activity of GLUT4 receptors; rather, it **enhances their role** in glucose transport. - Inhibition would lead to **reduced glucose uptake**, which is contrary to insulin's primary function in muscle cells. *Decreases glucose transport* - This statement is incorrect as insulin's main function in muscle cells is to **increase glucose uptake** to lower blood glucose levels. - Insulin promotes glucose transport by **increasing the availability** of GLUT4 transporters at the cell surface. *Activates lipolysis* - Insulin is a powerful **anabolic hormone** that generally inhibits lipolysis (fat breakdown) and promotes lipogenesis (fat synthesis). - Lipolysis is primarily activated by hormones like **glucagon and catecholamines**, not insulin.

Q: All of the following are true about the adrenal gland EXCEPT:

Medulla produces mineralocorticoids. ***Medulla produces mineralocorticoids*** - The **adrenal medulla** primarily produces **catecholamines** (epinephrine and norepinephrine), not mineralocorticoids. - **Mineralocorticoids** (like aldosterone) are secreted by the **zona glomerulosa** in the adrenal cortex. *Zona fasciculata secretes cortisol* - The **zona fasciculata** is the middle and largest layer of the adrenal cortex. - Its primary function is the secretion of **glucocorticoids**, mainly **cortisol**, which is crucial for stress response and metabolism. *Zona glomerulosa produces aldosterone* - The **zona glomerulosa** is the outermost layer of the adrenal cortex. - It is responsible for producing **mineralocorticoids**, with **aldosterone** being the most significant. *Zona reticularis secretes androgens* - The **zona reticularis** is the innermost layer of the adrenal cortex, adjacent to the medulla. - It primarily secretes **adrenal androgens** (like DHEA and androstenedione), which are precursors to sex hormones.

Q: Which hormone does not play a significant role in utero growth?

Growth hormone. ***Growth hormone*** - **Growth hormone (GH)** plays a crucial role in postnatal growth, but its direct impact on fetal growth is considered minor, as the **fetal pituitary gland** is not fully mature. - Fetal growth is primarily regulated by other factors like **insulin**, **insulin-like growth factors (IGFs)**, and nutrient supply. *Insulin* - **Insulin** is a major anabolic hormone in utero, promoting nutrient uptake and storage, leading to **fetal growth and glycogen synthesis**. - **Fetal hyperinsulinemia**, often seen in maternal diabetes, can lead to **macrosomia**. *Cortisol* - **Cortisol** is essential for **fetal lung maturation** and the development of several organ systems, thus indirectly influencing overall fetal viability and growth. - While high levels can potentially inhibit growth, physiological levels are crucial for normal development. *Thyroid hormone* - **Thyroid hormone** is critical for normal **fetal brain development** and skeletal maturation. - **Congenital hypothyroidism** can lead to significant developmental delays and poor growth.

Q: Which hormone inhibits appetite by acting on hypothalamus?

Leptin. ***Leptin*** - **Leptin** is a hormone produced by fat cells that acts on the hypothalamus to signal **satiety** and inhibit appetite. - Higher levels of leptin typically indicate sufficient energy stores, leading to reduced food intake and increased energy expenditure. *Ghrelin* - **Ghrelin** is primarily produced by the stomach and is known as the "**hunger hormone**" because it stimulates appetite, rather than inhibiting it. - Its levels rise before meals and fall after eating, signaling the brain to initiate food consumption. *Cortisol* - **Cortisol** is a steroid hormone produced by the adrenal glands, often associated with stress response, and can actually stimulate appetite, particularly for high-calorie foods. - It does not primarily function as an appetite-inhibiting hormone acting on the hypothalamus. *Insulin* - **Insulin** is a hormone produced by the pancreas that regulates blood glucose levels; while it can have some short-term effects on satiety, its primary role is not long-term appetite inhibition in the hypothalamus. - High insulin can initially suppress appetite, but chronically elevated insulin can sometimes contribute to **insulin resistance** and increased food intake.

Q: A patient presents with severe abdominal pain and hyperglycemia. Imaging reveals a mass in the pancreas. Which pancreatic cell type's dysfunction most likely explains the hyperglycemia?

Beta cells. ***Beta cells*** - **Beta cells** produce **insulin**, a hormone vital for lowering blood glucose by promoting glucose uptake into cells [1]. - Dysfunction or destruction of **beta cells** leads to insufficient insulin production, resulting in **hyperglycemia** (high blood sugar) [2]. *Alpha cells* - **Alpha cells** produce **glucagon**, a hormone that increases blood glucose levels by promoting **glycogenolysis** and **gluconeogenesis** in the liver [1]. - While glucagon excess can cause hyperglycemia, the primary cell type linked to the pancreatic mass and hyperglycemia in this context points to insulin deficiency. *Delta cells* - **Delta cells** produce **somatostatin**, which inhibits the secretion of both insulin and glucagon, as well as other gastrointestinal hormones [1]. - Dysfunction of delta cells is not typically associated with severe hyperglycemia as a primary symptom. *Acinar cells* - **Acinar cells** constitute the majority of the exocrine pancreas and produce **digestive enzymes** like amylase and lipase. - While a pancreatic mass could involve acinar cells, their primary role is in digestion, and their dysfunction alone does not directly cause hyperglycemia, although severe pancreatitis can secondarily affect islet cells.

Q: A patient presents with muscle weakness and fatigue. Laboratory results show hyperkalemia. Which hormone is most likely deficient in this patient?

Aldosterone. ***Aldosterone*** - **Aldosterone deficiency** leads to impaired renal potassium excretion, resulting in **hyperkalemia** [1]. - It also causes **sodium wasting** and **hypotension**, contributing to symptoms like fatigue and weakness due to **volume depletion** [1]. *Cortisol* - **Cortisol deficiency** (e.g., in Addison's disease) often presents with **hyponatremia**, **hypotension**, and generalized weakness, but typically does not cause hyperkalemia directly [1]. - While fatigue and weakness are prominent, severe hyperkalemia is not its primary metabolic derangement related to electrolyte balance. *Insulin* - **Insulin deficiency** (e.g., in Type 1 Diabetes) primarily leads to **hyperglycemia** and metabolic acidosis [1]. - Although it can cause electrolyte imbalances like **hypokalemia** (due to intracellular shift during treatment), it does not directly cause hyperkalemia via its primary mechanism of action. *Thyroxine (T4)* - **Thyroxine deficiency** (hypothyroidism) presents with symptoms such as fatigue, weight gain, cold intolerance, and bradycardia. - It does not directly cause **hyperkalemia**; electrolyte disturbances are not a prominent feature of primary hypothyroidism.

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

Increase blood calcium levels. ***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)**.

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

Parathyroid hormone. ***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 1

Serum prolactin levels are highest

Accepted Answer

During third trimester of pregnancy

Answer

24 hrs after parturition

Answer

REM sleep

Answer

In actively lactating mothers

Question 2

In females, the adrenal glands are the exclusive source for secretion of?

Accepted Answer

DHEAS

Answer

Testosterone

Answer

Estrogen

Answer

Progesterone

Question 3

What effect does insulin have on GLUT4 receptors in muscle cells?

Accepted Answer

Promotes their translocation to cell membrane

Answer

Inhibits their activity

Answer

Decreases glucose transport

Answer

Activates lipolysis

Question 4

All of the following are true about the adrenal gland EXCEPT:

Accepted Answer

Medulla produces mineralocorticoids

Answer

Zona fasciculata secretes cortisol

Answer

Zona glomerulosa produces aldosterone

Answer

Zona reticularis secretes androgens

Question 5

Which hormone does not play a significant role in utero growth?

Accepted Answer

Growth hormone

Answer

Insulin

Answer

Cortisol

Answer

Thyroid hormone

Question 6

Which hormone inhibits appetite by acting on hypothalamus?

Accepted Answer

Leptin

Answer

Ghrelin

Answer

Cortisol

Answer

Insulin

Question 7

A patient presents with severe abdominal pain and hyperglycemia. Imaging reveals a mass in the pancreas. Which pancreatic cell type's dysfunction most likely explains the hyperglycemia?

Accepted Answer

Beta cells

Answer

Alpha cells

Answer

Delta cells

Answer

Acinar cells

Question 8

A patient presents with muscle weakness and fatigue. Laboratory results show hyperkalemia. Which hormone is most likely deficient in this patient?

Accepted Answer

Aldosterone

Answer

Cortisol

Answer

Insulin

Answer

Thyroxine (T4)

Question 9

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

Accepted Answer

Increase blood calcium levels

Answer

Decrease blood phosphate levels

Answer

Decrease blood potassium levels

Answer

Increase blood sodium levels

Question 10

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

Accepted Answer

Parathyroid hormone

Answer

Insulin

Answer

Cortisol

Answer

Thyroxine

Endocrinology — MCQs

Endocrinology — MCQs

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