Endocrinology Practice Questions

Q: Hyperaldosteronism is associated with all, except:

Metabolic acidosis. ***Metabolic acidosis*** - **Hyperaldosteronism** leads to increased **potassium and hydrogen ion excretion** in the kidneys [1], resulting in **metabolic alkalosis**, not acidosis [2]. - The increased loss of hydrogen ions causes a rise in blood pH and bicarbonate levels [2]. *Hypernatremia* - Aldosterone promotes **sodium reabsorption** in the renal tubules, leading to increased plasma sodium concentration [1], [3]. - This increased sodium reabsorption contributes to the expansion of extracellular fluid volume and **hypertension** [3]. *Hypokalemia* - Aldosterone stimulates the **secretion of potassium ions** into the renal tubules, leading to excessive potassium loss in the urine [1]. - This sustained potassium excretion often results in **low serum potassium levels**. *Hypertension* - The increased reabsorption of **sodium and water** due to aldosterone action expands the extracellular fluid volume [3]. - This volume expansion directly contributes to elevated blood pressure, making hypertension a hallmark feature of **hyperaldosteronism** [2].

Q: What is the primary mechanism through which glucose stimulates insulin release?

Calcium influx. ***Calcium influx*** - Glucose metabolism in pancreatic beta cells leads to increased **ATP production**, which closes **ATP-sensitive potassium channels**. - This closing causes cell membrane depolarization, opening **voltage-gated calcium channels** and leading to an influx of calcium, triggering insulin granule exocytosis. *Cyclic AMP signaling* - While **cAMP** enhances glucose-stimulated insulin secretion, it is not the primary direct trigger. - cAMP primarily modulates the sensitivity of the exocytotic machinery to calcium. *Insulin receptor activation* - **Insulin receptors** are primarily found on target cells (e.g., muscle, fat, liver) and mediate insulin's metabolic effects, not its release. - Activating insulin receptors on beta cells would typically lead to a negative feedback rather than direct stimulation of insulin release. *ATP-sensitive potassium channel activation* - **Activation** of these channels would lead to hyperpolarization and reduced insulin secretion. - The primary mechanism of glucose-stimulated insulin release involves the **inhibition** (closure) of these channels, not their activation.

Q: Which hormone is primarily synthesized by the supraoptic nucleus of the hypothalamus?

Antidiuretic hormone. ***Antidiuretic hormone*** - The **supraoptic nucleus** of the hypothalamus is the primary site for the synthesis of **antidiuretic hormone (ADH)**, also known as vasopressin. - Approximately **80% of supraoptic neurons** produce ADH, making it the predominant hormone synthesized by this nucleus. - ADH is crucial for **water reabsorption** in the kidneys, regulating plasma osmolality and blood pressure. *Oxytocin* - While **oxytocin** is also synthesized in the supraoptic nucleus (approximately 20% of neurons), it is produced in much greater quantities by the **paraventricular nucleus**. - The paraventricular nucleus is the **primary source** of oxytocin, which is important for **uterine contractions** during labor and **milk ejection** during lactation. *Growth hormone* - **Growth hormone (GH)** is produced by the **anterior pituitary gland** under the control of **growth hormone-releasing hormone (GHRH)** and **somatostatin** from the hypothalamus. - It is not synthesized by the supraoptic nucleus. *Adrenocorticotropic hormone* - **Adrenocorticotropic hormone (ACTH)** is secreted by the **anterior pituitary gland** in response to **corticotropin-releasing hormone (CRH)** from the hypothalamus. - The supraoptic nucleus is not involved in its synthesis or direct regulation.

Q: What hormone is secreted by the delta cells of the pancreas?

Somatostatin. ***Somatostatin*** - **Delta cells** (δ cells) of the pancreas are responsible for secreting **somatostatin**. - Somatostatin acts as a general **inhibitory hormone**, suppressing the release of other hormones, including insulin and glucagon, and regulating gastrointestinal function. *Cholecystokinin* - **Cholecystokinin (CCK)** is primarily produced by cells in the **duodenum** and jejunum, not the pancreas. - It stimulates the release of **bile** and **pancreatic enzymes** in response to fats and proteins. *Gastrin* - **Gastrin** is secreted by **G cells** mainly in the **antrum of the stomach**, not the pancreas. - It stimulates the secretion of **gastric acid** and promotes mucosal growth in the stomach. *Insulin* - **Insulin** is secreted by the **beta cells** (β cells) of the pancreatic islets, which are distinct from the delta cells. - Its primary role is to lower blood glucose levels by promoting glucose uptake into cells.

Q: Which hormone is released when serum calcium levels decrease?

Parathormone. ***Parathormone*** - **Parathormone (PTH)** is released from the **parathyroid glands** in response to **low serum calcium levels**. - Its primary function is to **increase serum calcium** by stimulating bone resorption, increasing renal reabsorption of calcium, and enhancing intestinal absorption of calcium (indirectly via vitamin D activation). *Calcitonin* - **Calcitonin** is released from the **thyroid gland** in response to **high serum calcium levels**. - Its main action is to **lower serum calcium** by inhibiting osteoclast activity and increasing renal calcium excretion. *Thyroxine* - **Thyroxine (T4)** is a thyroid hormone primarily involved in **metabolism**, growth, and development. - It does **not directly regulate** serum calcium levels. *Adrenaline* - **Adrenaline (epinephrine)** is a hormone released from the **adrenal glands** in response to stress. - It plays a role in the "fight or flight" response, affecting heart rate, blood pressure, and glucose metabolism, but **not calcium regulation**.

Q: Growth hormone secretion is increased by what?

Hypoglycemia. ***Hypoglycemia*** - **Hypoglycemia** (low blood glucose) is a **potent stimulus for growth hormone secretion**. - GH acts as a counter-regulatory hormone to raise blood glucose by promoting gluconeogenesis and reducing glucose uptake in peripheral tissues. - This is a physiological response to maintain blood glucose homeostasis during fasting or hypoglycemic states. *Somatostatin* - **Somatostatin** (also known as growth hormone-inhibiting hormone) directly **inhibits the release of growth hormone** from the anterior pituitary. - It acts as a negative regulator of GH secretion, not a stimulator. *Hyperglycemia* - **Hyperglycemia** (high blood glucose levels) **inhibits growth hormone secretion**. - This negative feedback mechanism prevents excessive GH-mediated glucose elevation when blood glucose is already high. *Obesity* - **Obesity** is associated with **reduced basal and stimulated growth hormone secretion**. - Multiple mechanisms contribute to this, including increased free fatty acids, altered hypothalamic-pituitary function, and increased negative feedback from IGF-1.

Q: Insulin is required for glucose transport in all of the following tissues except:

RBC. ***RBC*** - **Red blood cells** transport glucose via **GLUT1 transporters**, which are insulin-independent. - This ensures a constant supply of glucose to RBCs for their energy needs, regardless of insulin levels. *Skeletal muscles* - **Skeletal muscle cells** rely on **GLUT4 transporters** for glucose uptake, which are highly **insulin-dependent**. - During exercise, muscle contraction can also stimulate GLUT4 translocation, increasing glucose uptake even without high insulin levels. *Adipose tissue* - **Adipose tissue** also primarily uses **GLUT4 transporters** for glucose uptake, making it highly **insulin-dependent**. - Insulin promotes glucose conversion into fatty acids for storage within adipocytes. *Heart muscles* - **Cardiac muscle cells** also use **GLUT4 transporters** for a significant portion of their glucose uptake, therefore exhibiting **insulin dependence**. - While they can utilize fatty acids as a primary energy source, glucose uptake increases in response to insulin, particularly during periods of high demand.

Q: Which hormone, together with the catecholamines, enhances the tone of vascular smooth muscle and assists in elevating blood pressure?

Cortisol. ***Cortisol*** - **Cortisol** potentiates the effects of **catecholamines** on **vascular smooth muscle**, leading to increased vasoconstriction and **elevated blood pressure**. - This **synergistic action** is crucial for maintaining vascular tone and immediate blood pressure regulation during stress. *Parathyroid hormone (PTH)* - **PTH** primarily regulates **calcium and phosphate** homeostasis by acting on bone, kidneys, and indirectly on the intestines. - It does not directly cause vasoconstriction or significantly interact with catecholamines to elevate blood pressure. *Glucagon (GCG)* - **Glucagon's** main role is to increase **blood glucose levels** by stimulating hepatic **glycogenolysis** and gluconeogenesis. - While it can have some chronotropic and inotropic effects on the heart, it is not a primary vasoconstrictor or a significant enhancer of catecholamine-mediated vascular tone. *Thyroxine (T4)* - **Thyroxine (T4)** and **triiodothyronine (T3)** play a broad role in **metabolism**, growth, and development. - While thyroid hormones can increase cardiac output and sensitivity to catecholamines, they do not directly enhance vascular smooth muscle tone in the same way cortisol does as a primary pressor.

Q: What is the primary effect of GLP-1 on insulin secretion?

Increased insulin secretion from beta-cells of pancreas. ***Increased insulin secretion from beta-cells of pancreas*** - **Glucagon-like peptide-1 (GLP-1)** is an **incretin hormone** that stimulates **glucose-dependent insulin secretion** from pancreatic beta-cells. - This effect is crucial for maintaining **glucose homeostasis**, especially after a meal. *Increased aldosterone secretion by adrenal* - **Aldosterone secretion** is primarily regulated by the **renin-angiotensin-aldosterone system (RAAS)** and potassium levels, not directly by GLP-1. - Aldosterone's main function is to regulate **sodium and water balance** and **blood pressure**. *Increased PTH secretion* - **Parathyroid hormone (PTH)** secretion is primarily regulated by **serum calcium levels**. - Its main role is to maintain **calcium homeostasis** by affecting bone, kidney, and intestine. *Increased testosterone secretion from Leydig cells* - **Testosterone secretion** from Leydig cells is primarily regulated by **luteinizing hormone (LH)** from the pituitary gland. - GLP-1 has no direct significant role in **gonadal steroidogenesis**.

Q: The hypothalamus produces several releasing peptides. Which releasing peptide is responsible for the release of adrenocorticotropic hormone (ACTH) from the pituitary?

Corticotropin-releasing factor (CRF). ***Corticotropin-releasing factor (CRF)*** - **Corticotropin-releasing factor** (CRF) is a hypothalamic releasing hormone that stimulates the **anterior pituitary gland** to secrete **adrenocorticotropic hormone (ACTH)**. - ACTH then acts on the adrenal cortex to stimulate the production of glucocorticoids, particularly **cortisol**. *Somatostatin* - **Somatostatin** is a hypothalamic hormone that primarily **inhibits** the release of growth hormone (GH) and thyroid-stimulating hormone (TSH) from the anterior pituitary. - It does not directly regulate the release of ACTH. *Corticosterone* - **Corticosterone** is a **glucocorticoid hormone** produced by the adrenal cortex, similar to cortisol, but it is not a hypothalamic releasing peptide. - It plays a role in stress response and metabolism but does not directly stimulate ACTH release from the pituitary; rather, its production is stimulated by ACTH. *Cortisol* - **Cortisol** is the primary **glucocorticoid** produced by the adrenal cortex in humans. - Its release is stimulated by ACTH, and it acts via a **negative feedback loop** to inhibit the release of both CRF from the hypothalamus and ACTH from the pituitary.

Question 1

Hyperaldosteronism is associated with all, except:

Accepted Answer

Metabolic acidosis

Answer

Hypernatremia

Answer

Hypertension

Answer

Hypokalemia

Question 2

What is the primary mechanism through which glucose stimulates insulin release?

Accepted Answer

Calcium influx

Answer

Cyclic AMP signaling

Answer

Insulin receptor activation

Answer

ATP-sensitive potassium channel activation

Question 3

Which hormone is primarily synthesized by the supraoptic nucleus of the hypothalamus?

Accepted Answer

Antidiuretic hormone

Answer

Oxytocin

Answer

Growth hormone

Answer

Adrenocorticotropic hormone

Question 4

What hormone is secreted by the delta cells of the pancreas?

Accepted Answer

Somatostatin

Answer

Gastrin

Answer

Insulin

Answer

Cholecystokinin

Question 5

Which hormone is released when serum calcium levels decrease?

Accepted Answer

Parathormone

Answer

Calcitonin

Answer

Thyroxine

Answer

Adrenaline

Question 6

Growth hormone secretion is increased by what?

Accepted Answer

Hypoglycemia

Answer

Somatostatin

Answer

Obesity

Answer

Hyperglycemia

Question 7

Insulin is required for glucose transport in all of the following tissues except:

Accepted Answer

RBC

Answer

Skeletal muscles

Answer

Adipose tissue

Answer

Heart muscles

Question 8

Which hormone, together with the catecholamines, enhances the tone of vascular smooth muscle and assists in elevating blood pressure?

Accepted Answer

Cortisol

Answer

Parathyroid hormone (PTH)

Answer

Glucagon (GCG)

Answer

Thyroxine (T4)

Question 9

What is the primary effect of GLP-1 on insulin secretion?

Accepted Answer

Increased insulin secretion from beta-cells of pancreas

Answer

Increased aldosterone secretion by adrenal

Answer

Increased PTH secretion

Answer

Increased testosterone secretion from Leydig cells

Question 10

The hypothalamus produces several releasing peptides. Which releasing peptide is responsible for the release of adrenocorticotropic hormone (ACTH) from the pituitary?

Accepted Answer

Corticotropin-releasing factor (CRF)

Answer

Somatostatin

Answer

Cortisol

Answer

Corticosterone

Endocrinology — MCQs

Endocrinology — MCQs

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