Endocrinology Practice Questions

Q: The hormone that links obesity and puberty

Leptin. ***Leptin*** - **Leptin** is a hormone produced by **adipose tissue** (fat cells) that signals satiety and plays a crucial role in regulating energy balance. Because it is directly proportional to the amount of body fat, higher levels associated with **obesity** can accelerate the onset of puberty. - High leptin levels are thought to signal to the **hypothalamus** that there are sufficient energy reserves for reproduction, thereby triggering the cascade of hormonal events necessary for **puberty**. *Ghrelin* - **Ghrelin** is an appetite-stimulating hormone primarily produced in the stomach, often referred to as the "**hunger hormone.**" - It does not directly link obesity with the initiation of puberty; its primary role is in short-term appetite regulation and energy homeostasis. *Thyroid hormone* - **Thyroid hormones** (T3 and T4) are essential for **growth, development**, and **metabolic rate**. - While thyroid dysfunction can affect overall growth and energy metabolism, it does not directly link obesity to the timing of puberty initiation. *Growth hormone* - **Growth hormone (GH)** is critical for linear growth during childhood and adolescence and influences metabolism. - While GH is vital for overall development, it does not directly mediate the connection between the *amount of adipose tissue* and the *onset of puberty* in the way leptin does.

Q: Regarding thyroid hormone all are true except:

T4 has shorter half life than T3. ***T4 has shorter half-life than T3*** - This statement is incorrect because **T4 (thyroxine) has a significantly longer half-life (approximately 7 days)** compared to **T3 (triiodothyronine), which has a half-life of about 1-2 days**. - The longer half-life of T4 allows for a more stable and sustained effect, acting as a prohormone. *T4 has the maximum plasma concentration* - **T4 is secreted in much larger quantities from the thyroid gland than T3 (about 80% T4 vs. 20% T3)**, leading to a higher concentration in the plasma. - This high plasma concentration of T4 makes it the primary circulating thyroid hormone, mostly bound to plasma proteins. *T3 is more avidly bound to nuclear receptors than T4* - **T3 binds to nuclear thyroid hormone receptors with 10 to 15 times greater affinity than T4**, making it the more potent and biologically active form. - This stronger binding affinity is crucial for T3's direct physiological effects on target cells. *T3 is more active than T4* - **T3 is considered the metabolically active form of thyroid hormone**, directly mediating most physiological effects by binding to nuclear receptors. - T4 acts largely as a **prohormone**, being deiodinated in peripheral tissues to form T3, which then exerts metabolic activity.

Q: Which of the following compounds antagonizes the actions of insulin?

Growth hormone. ***Growth hormone*** - **Growth hormone (GH)** is a potent **anti-insulin hormone** that raises blood glucose by promoting **gluconeogenesis** and reducing glucose utilization by peripheral tissues. - It decreases **insulin sensitivity** in target tissues like muscle and adipose tissue, often leading to a temporary state of **insulin resistance**. *Substance P* - **Substance P** is a **neuropeptide** involved in pain transmission and inflammation, and its primary actions do not directly involve glucose metabolism or insulin antagonism. - While it can influence local metabolic processes, it does not exert systemic effects on insulin action. *Neuropeptide Y* - **Neuropeptide Y (NPY)** is a **neurotransmitter** primarily involved in stimulating appetite and reducing energy expenditure, playing a role in weight regulation. - Although it affects metabolic balance, NPY does not directly antagonize insulin's actions on glucose uptake or utilization. *Vasoactive intestinal peptide* - **Vasoactive intestinal peptide (VIP)** is a **neurotransmitter** and hormone that primarily affects smooth muscle relaxation, exocrine and endocrine secretions, and local blood flow. - It does not directly antagonize insulin's effects on glucose metabolism or directly impact insulin sensitivity in a significant way.

Q: Sympathetic stimulation has the following effect on insulin release

Inhibition. ***Inhibition*** - **Sympathetic nervous system** activation primarily leads to **inhibition** of insulin release through **alpha-2 adrenergic receptors** on pancreatic beta cells. - This effect is crucial during stress or exercise, as it helps to conserve glucose for vital organs by limiting its uptake into peripheral tissues. *Inhibition followed by stimulation* - While sympathetic activation primarily inhibits insulin release, there can be a **minor stimulatory effect** via **beta-2 adrenergic receptors** at higher concentrations of catecholamines or in specific physiological contexts, but the predominant initial effect is inhibition. - This option does not represent the primary and immediate action of typical sympathetic stimulation on insulin secretion. *No effect* - This is incorrect as the pancreatic beta cells are richly innervated by the **autonomic nervous system**, and sympathetic activity has a well-established direct influence on insulin secretion. - The body's need to regulate blood glucose tightly under stress or activity necessitates a direct effect from the sympathetic nervous system. *Stimulation* - **Stimulation of insulin release** is predominantly mediated by the **parasympathetic nervous system** (via acetylcholine) and high blood glucose levels. - Sympathetic stimulation generally exerts a counter-regulatory effect to ensure glucose availability during periods of increased demand.

Q: At the cellular level the physiological effects of human growth hormone are mediated by?

Insulin-like growth factors. ***Insulin-like growth factors*** - The primary mechanism by which **growth hormone (GH)** exerts its physiological effects is by stimulating the production of **insulin-like growth factors (IGFs)**, particularly **IGF-1**. - **IGF-1** then mediates most of the **growth-promoting actions** of GH on target tissues through the **somatomedin hypothesis**. *Insulin* - **Insulin** is a hormone primarily involved in regulating **glucose metabolism** by promoting glucose uptake and utilization by cells. - While GH can influence **insulin sensitivity**, insulin itself does not mediate the primary growth-promoting effects of GH. *Prolactin* - **Prolactin** is a hormone primarily associated with **lactation** and **mammary gland development**. - It has distinct functions from growth hormone and does not mediate its growth-promoting actions. *Somatotropin* - **Somatotropin** is simply another name for **human growth hormone (hGH)** itself. - The question asks how the effects *of* growth hormone are mediated at the cellular level, implying a **downstream mediator**, not the hormone itself.

Q: Which of the following is true about somatostatin, insulin, and glucagon?

Somatostatin blocks release of insulin and glucagon.. ***Somatostatin blocks release of insulin and glucagon.*** - **Somatostatin** acts as a paracrine inhibitor within the **islets of Langerhans**, suppressing the secretion of both **insulin** from beta cells and **glucagon** from alpha cells. - This inhibitory action helps to modulate and fine-tune nutrient absorption and utilization following a meal, preventing excessive fluctuations in blood glucose levels. *Glucagon blocks insulin and Somatostatin release.* - **Glucagon's primary role** is to raise blood glucose by stimulating **hepatic glucose production**, not to block the release of insulin or somatostatin. - In fact, glucagon can stimulate **somatostatin release**, which then acts to inhibit glucagon secretion, forming a negative feedback loop. *Insulin increases glucagon release.* - **Insulin and glucagon** have opposing roles in glucose regulation; insulin's main function is to lower blood glucose, while glucagon raises it. - High insulin levels typically **suppress glucagon secretion**, as the body needs to lower glucose, not raise it further. *Somatostatin stimulates insulin.* - **Somatostatin** is a potent **inhibitor** of insulin release, not a stimulator. - This inhibitory effect helps to prevent rapid and excessive insulin secretion, which could lead to hypoglycemia.

Q: In surgical stress all hormones are increased except:

Insulin. ***Insulin*** - While other **stress hormones** increase, **insulin** levels typically **decrease** or remain stable due to increased **insulin resistance** during surgical stress. - This physiological response aims to maintain **blood glucose** levels for energy during heightened metabolic demands. *Epinephrine* - **Epinephrine** (adrenaline) is a key **catecholamine** released during surgical stress, leading to a "fight or flight" response. - It increases **heart rate**, **blood pressure**, and promotes **gluconeogenesis** to supply quick energy. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is released from the **pituitary gland** in response to surgical stress. - **ACTH** stimulates the adrenal cortex to produce **cortisol**, a critical stress hormone. *Cortisol* - **Cortisol** levels significantly rise during surgical stress, mediated by **ACTH** release. - It plays a crucial role in **modulating inflammation**, **glucose metabolism**, and maintaining **hemodynamic stability**.

Q: Aldosterone secretion is maximally stimulated by?

Hyperkalemia. ***Hyperkalemia*** - **Hyperkalemia is the most potent direct stimulator** of aldosterone secretion from the zona glomerulosa cells of the adrenal cortex. - Even a small increase in serum potassium (0.1 mEq/L) can significantly increase aldosterone synthesis and secretion. - This is a crucial homeostatic mechanism to promote **renal potassium excretion** via principal cells in the collecting duct, normalizing serum potassium levels. - **Mechanism**: K+ directly depolarizes zona glomerulosa cells → opens voltage-gated Ca2+ channels → increases intracellular Ca2+ → stimulates aldosterone synthesis. *Exogenous steroids* - Exogenous glucocorticoids **suppress the hypothalamic-pituitary-adrenal (HPA) axis** through negative feedback. - They do not stimulate aldosterone secretion; instead, they reduce endogenous corticosteroid production. - Some synthetic steroids may have mineralocorticoid activity themselves, but they don't stimulate endogenous aldosterone. *ACTH* - ACTH has only a **permissive role** in aldosterone secretion, not a primary regulatory role. - While ACTH is required for maintaining the structural integrity of the zona glomerulosa, it is **not the maximal stimulator**. - ACTH primarily regulates **cortisol synthesis** from the zona fasciculata. - The major physiological regulators of aldosterone are **hyperkalemia** and **angiotensin II** (via the renin-angiotensin system). *Hypernatremia* - **Hypernatremia inhibits aldosterone secretion** rather than stimulating it. - Since aldosterone's primary action is to increase sodium reabsorption, elevated sodium levels signal the body to reduce aldosterone to prevent further sodium retention. - This is part of the negative feedback mechanism for sodium homeostasis.

Q: All of the following statements about Insulin like Growth factor - 1 are true, except:

Mainly secreted by the pancreas. ***Mainly secreted by the pancreas*** - **Insulin-like Growth Factor-1 (IGF-1)** is primarily produced by the **liver** in response to **growth hormone (GH)** stimulation, not the pancreas. - While the pancreas does produce some growth factors and hormones, IGF-1 synthesis is predominantly hepatic. *Required for skeletal and cartilage growth* - IGF-1 is a crucial mediator of **growth hormone's effects**, playing a significant role in **linear growth, bone formation**, and **cartilage maintenance**. - It promotes **cell proliferation** and differentiation in various tissues, including bone and cartilage. *Secretion is stimulated by Growth Hormone* - **Growth hormone (GH)** from the pituitary gland stimulates the liver and other tissues to produce IGF-1. - IGF-1 then mediates many of the growth-promoting actions of GH. *Also known as Somatomedin C* - **Somatomedin C** is an older name for **Insulin-like Growth Factor-1 (IGF-1)**. - This term reflects its **growth-promoting actions** and its similarity in structure to **insulin**.

Q: Insulin-mediated transport of glucose is seen in:

Seen in adipose tissue. ***Seen in adipose tissue*** - **Adipose tissue** (fat cells) and muscle cells significantly increase their uptake of glucose in response to **insulin**. - This transport is mediated by **GLUT4 transporters**, which are translocated to the cell membrane upon insulin binding. *Main Mechanism in RBCs* - **Red blood cells (RBCs)** primarily utilize **GLUT1 transporters** for glucose uptake. - **GLUT1** is constitutive and **insulin-independent**, meaning its activity is not regulated by insulin. *All are true* - This option is incorrect because the statement regarding RBCs is false, making the collective "all are true" statement inaccurate. *Via GLUT-2* - **GLUT2** is a primary transporter in the **liver, pancreatic β-cells, intestinal epithelial cells**, and **kidney**. - While it facilitates glucose transport, **GLUT2 is insulin-independent** and has a low affinity but high capacity for glucose, primarily involved in sensing and buffering glucose levels rather than insulin-mediated uptake in peripheral tissues.

Question 1

The hormone that links obesity and puberty

Accepted Answer

Leptin

Answer

Ghrelin

Answer

Thyroid hormone

Answer

Growth hormone

Question 2

Regarding thyroid hormone all are true except:

Accepted Answer

T4 has shorter half life than T3

Answer

T4 has the maximum plasma concentration

Answer

T3 is more avidly bound to nuclear receptors than T4

Answer

T3 is more active than T4

Question 3

Which of the following compounds antagonizes the actions of insulin?

Accepted Answer

Growth hormone

Answer

Substance P

Answer

Neuropeptide Y

Answer

Vasoactive intestinal peptide

Question 4

Sympathetic stimulation has the following effect on insulin release

Accepted Answer

Inhibition

Answer

Inhibition followed by stimulation

Answer

No effect

Answer

Stimulation

Question 5

At the cellular level the physiological effects of human growth hormone are mediated by?

Accepted Answer

Insulin-like growth factors

Answer

Insulin

Answer

Prolactin

Answer

Somatotropin

Question 6

Which of the following is true about somatostatin, insulin, and glucagon?

Accepted Answer

Somatostatin blocks release of insulin and glucagon.

Answer

Glucagon blocks insulin and Somatostatin release.

Answer

Insulin increases glucagon release.

Answer

Somatostatin stimulates insulin.

Question 7

In surgical stress all hormones are increased except:

Accepted Answer

Insulin

Answer

Epinephrine

Answer

ACTH

Answer

Cortisol

Question 8

Aldosterone secretion is maximally stimulated by?

Accepted Answer

Hyperkalemia

Answer

Exogenous steroids

Answer

ACTH

Answer

Hypernatremia

Question 9

All of the following statements about Insulin like Growth factor - 1 are true, except:

Accepted Answer

Mainly secreted by the pancreas

Answer

Required for skeletal and cartilage growth

Answer

Secretion is stimulated by Growth Hormone

Answer

Also known as Somatomedin C

Question 10

Insulin-mediated transport of glucose is seen in:

Accepted Answer

Seen in adipose tissue

Answer

Main Mechanism in RBCs

Answer

All are true

Answer

Via GLUT-2

Endocrinology — MCQs

Endocrinology — MCQs

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