Endocrinology Practice Questions

Q: Enteroinsular axis is mediated through:

GLP-1. ***GLP-1*** - **Glucagon-like peptide-1 (GLP-1)** is a key **incretin hormone** that mediates the enteroinsular axis by enhancing glucose-dependent insulin secretion from pancreatic beta cells. - It is released from intestinal L-cells in response to nutrient intake, linking nutrient sensing in the gut directly to pancreatic insulin secretion. *Glucagon* - **Glucagon** is a hormone primarily involved in raising **blood glucose** levels, released by pancreatic alpha cells, and acts in opposition to insulin. - While it plays a role in glucose homeostasis, it does not primarily mediate the **enteroinsular axis's** enhancement of insulin secretion. *Nitric oxide* - **Nitric oxide (NO)** is a gaseous signaling molecule involved in various physiological processes, including **vasodilation** and neurotransmission. - It is not considered a primary mediator of the **enteroinsular axis** or incretin effect. *VIP* - **Vasoactive intestinal peptide (VIP)** is a **neuropeptide** that acts as a neurotransmitter and neurohormone, involved in gut motility and secretion. - While it can influence pancreatic function, it is not the main mediator of the **enteroinsular axis** that links nutrient sensing in the gut to enhanced insulin secretion.

Q: Which of the following inhibit gonadotropin-releasing hormone pulse secretion?

Prolactin. ***Prolactin*** - Elevated levels of **prolactin** inhibit the pulsatile secretion of **gonadotropin-releasing hormone (GnRH)** from the hypothalamus. - This inhibition leads to decreased production of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)** from the pituitary, ultimately affecting gonadal function. *Thyroxine* - **Thyroxine** (thyroid hormone) primarily regulates metabolism and growth, and while it interacts with the reproductive axis, its direct effect is not typically the **inhibition of GnRH pulse secretion**. - Extreme thyroid dysfunction can indirectly impact reproductive hormones, but it's not the primary mechanism of GnRH inhibition. *Oxytocin* - **Oxytocin** is largely involved in **uterine contractions** during labor and **milk ejection** during lactation, and has roles in social bonding. - It does not directly inhibit the pulsatile release of **GnRH**. *Insulin* - **Insulin** is a key hormone in **glucose metabolism** and energy regulation. - While insulin resistance and hyperinsulinemia can affect reproductive function (e.g., in polycystic ovary syndrome, PCOS), it does not **directly inhibit GnRH pulse secretion**.

Q: Which of the following substances is stored in a cell?

Insulin. ***Insulin*** - Insulin is a **peptide hormone** synthesized as **proinsulin** and then cleaved into active insulin, which is stored in **secretory granules** within pancreatic **beta cells** before release. - Its storage in vesicles allows for prompt release in response to stimuli like high blood glucose, enabling rapid regulation of **glucose metabolism**. - Insulin represents the **classic example** of intracellular hormone storage in medical physiology. *Cortisol* - Cortisol is a **steroid hormone**, synthesized from **cholesterol** in the adrenal cortex. Steroid hormones are **lipid-soluble** and **not stored** in vesicles; they are released immediately upon synthesis. - Its production is regulated by the **hypothalamic-pituitary-adrenal (HPA) axis**, with synthesis occurring on demand rather than being stored. *Thyroxine* - Thyroxine (T4) is a **thyroid hormone** produced by follicular cells of the thyroid gland, but it is **stored extracellularly** as part of **thyroglobulin** in the colloid, not inside cells in secretory vesicles. - Before release, T4 must be cleaved from thyroglobulin and then secreted, which is distinct from intracellular storage. *Renin* - Renin is an **enzyme** produced by the **juxtaglomerular cells** of the kidney. While renin is stored in granules within these cells, it functions as a **proteolytic enzyme** in the blood rather than as a typical hormone acting on distant receptors. - Its primary role is to cleave **angiotensinogen** in the bloodstream, initiating the **renin-angiotensin-aldosterone system** for blood pressure regulation. - In the context of cellular physiology, **insulin** is the prototypical example of a stored substance due to its role as a classical hormone with direct metabolic effects.

Q: Which hormone directly lowers blood calcium levels?

Calcitonin. ***Calcitonin*** - **Calcitonin** is a hormone secreted by the **parafollicular C cells** of the thyroid gland. - Its primary function is to **lower blood calcium levels** by inhibiting osteoclast activity and promoting calcium excretion by the kidneys. - It is the only hormone that directly acts to **decrease serum calcium**. *Parathyroid hormone* - **PTH** is secreted by the parathyroid glands and has the **opposite effect** to calcitonin. - It **increases blood calcium levels** by stimulating osteoclast activity, increasing renal calcium reabsorption, and activating vitamin D. *1,25-dihydroxycholecalciferol* - This is the **active form of vitamin D**, also known as **calcitriol**. - Its main roles are to **increase blood calcium levels** by enhancing calcium absorption from the intestine and promoting bone resorption. *Vitamin D* - **Vitamin D** (cholecalciferol or ergocalciferol) is a precursor that needs to be metabolized into its active form, 1,25-dihydroxycholecalciferol. - Its ultimate effect (via its active form) is to **raise blood calcium levels**, not lower them.

Q: Increased insulin is characterized by all of the following, except:

Increased Glucagon secretion. ***Increased Glucagon secretion*** - **Insulin** primarily functions to lower blood glucose, and its release is typically inhibited by factors that trigger **glucagon** secretion, which aims to raise blood glucose. - Increased insulin would generally lead to **decreased glucagon secretion** as the body attempts to maintain glucose homeostasis. *Increased Intracellular potassium* - Insulin promotes the uptake of **potassium** into cells, particularly muscle and liver cells, by stimulating the **Na+/K+ ATPase pump**. - This action helps to lower serum potassium levels and can be utilized therapeutically in cases of hyperkalemia. *Hypoglycemia* - **Insulin** is the primary hormone responsible for lowering blood glucose levels by promoting glucose uptake by cells and inhibiting hepatic glucose production. - Excess insulin, whether endogenous or exogenous, can lead to **hypoglycemia** if glucose intake does not match insulin action. *Enhanced fatty acid synthesis* - **Insulin** is an anabolic hormone that promotes energy storage, including the conversion of excess glucose into **fatty acids** in the liver and adipose tissue. - This process, known as lipogenesis, is a key mechanism by which insulin contributes to the storage of energy reserves.

Q: What is the effect of cortisol on bone metabolism?

Decreased bone matrix. ***Decreased bone matrix*** - Cortisol **inhibits osteoblast activity** and **promotes osteoblast apoptosis**, leading to reduced production of bone matrix components like collagen - It also **increases osteoclast activity**, further contributing to bone breakdown and resulting in a net decrease in bone matrix - This mechanism is the primary cause of **glucocorticoid-induced osteoporosis** *Increases calcium absorption* - Cortisol actually **decreases intestinal calcium absorption** by reducing the sensitivity of the intestines to vitamin D - This effect contributes to **negative calcium balance** and exacerbates bone loss *Stimulates osteoblast activity* - Cortisol has an **inhibitory effect on osteoblast differentiation and function**, leading to reduced bone formation - This suppression of osteoblasts is the opposite of this option and directly contributes to weaker bones *Increased bone matrix* - This is incorrect as cortisol leads to **net bone loss**, not an increase, by inhibiting bone formation and accelerating bone resorption - An increase in bone matrix would require enhanced osteoblast activity, which is the opposite of cortisol's effect

Q: Intake of exogenous steroids causes

Adrenal insufficiency. ***Adrenal insufficiency*** - Exogenous steroids suppress the **hypothalamic-pituitary-adrenal (HPA) axis** through **negative feedback mechanism**. - Chronic use leads to **decreased ACTH secretion**, causing **adrenal cortex atrophy** and **secondary adrenal insufficiency**. - The adrenal glands lose their ability to produce adequate **endogenous cortisol**, creating a state of functional adrenal insufficiency. - This is why **gradual tapering** is essential when discontinuing steroids to allow HPA axis recovery. *Prolonged glucocorticoid exposure* - This is not a consequence but rather a **description of the treatment itself** (tautological). - Taking exogenous steroids IS glucocorticoid exposure, not something it causes. - This option confuses the intervention with its consequences. *Catecholamine excess* - Catecholamines (epinephrine, norepinephrine) are produced by the **adrenal medulla**. - Exogenous steroids **do not affect** catecholamine production or secretion. - Catecholamine excess occurs in conditions like **pheochromocytoma**, unrelated to steroid use. *Hyperaldosteronism* - This involves **excessive aldosterone** production, causing **hypertension** and **hypokalemia**. - Most exogenous steroids are **glucocorticoids** with minimal mineralocorticoid activity. - While some synthetic steroids have mineralocorticoid effects at high doses, **hyperaldosteronism is not the primary consequence** of exogenous steroid intake.

Q: In a person who has fasted for 5 days, all are seen except:

GH levels decreased. ***GH levels decreased*** - During **prolonged fasting**, **growth hormone (GH) levels** typically **increase** to help spare glucose and promote lipolysis, not decrease. - GH's role in counter-regulation means it helps maintain blood glucose by decreasing glucose utilization and increasing liver glucose production. *Glucose tolerance decreased* - **Prolonged fasting** leads to **decreased glucose tolerance** due to **insulin resistance** in peripheral tissues. - This resistance is a physiological adaptation to conserve glucose for the brain and to utilize fatty acids as primary fuel. *Immunoreactive insulin decreased* - Fasting, particularly for an extended duration, results in significantly **decreased insulin secretion** due to the absence of glucose intake. - Lower insulin levels facilitate the mobilization of stored energy, such as fatty acids and amino acids. *Free fatty acids (plasma) increased* - During extended fasting, **lipolysis** is significantly upregulated, leading to a substantial **increase in plasma free fatty acids**. - These fatty acids become the primary fuel source for many tissues, sparing glucose for organs like the brain.

Q: What is the primary mechanism by which corticosteroids affect calcium levels in the body?

Decreased absorption from gut. ***Decreased absorption from gut*** - This is the **primary mechanism** by which corticosteroids affect calcium homeostasis - Corticosteroids directly **antagonize vitamin D action** in the intestinal mucosa, reducing calcium absorption - They decrease the expression of **calcium-binding proteins** (calbindins) in the gut - This impaired intestinal absorption is the **predominant mechanism** contributing to corticosteroid-induced hypocalcemia and osteoporosis *Increased excretion from kidney* - While corticosteroids do increase renal calcium excretion by decreasing tubular reabsorption, this is a **secondary mechanism** - The renal effects are less significant than the intestinal absorption defect - This contributes to but is not the primary mechanism of calcium loss *No significant effect* - This is completely incorrect - Corticosteroids have **profound effects on calcium homeostasis**, leading to hypocalcemia and increased risk of osteoporosis - These effects are a major clinical concern in long-term corticosteroid therapy *Decreased plasma calcium level* - This describes the **result** of corticosteroid action, not the mechanism - The question asks for the mechanism by which corticosteroids *affect* calcium levels - Decreased plasma calcium is the consequence of reduced intestinal absorption and increased renal excretion

Question 1

Enteroinsular axis is mediated through:

Accepted Answer

GLP-1

Answer

Nitric oxide

Answer

Glucagon

Answer

VIP

Question 2

Which of the following inhibit gonadotropin-releasing hormone pulse secretion?

Accepted Answer

Prolactin

Answer

Oxytocin

Answer

Thyroxine

Answer

Insulin

Question 3

Which of the following substances is stored in a cell?

Accepted Answer

Insulin

Answer

Thyroxine

Answer

Renin

Answer

Cortisol

Question 4

Which hormone directly lowers blood calcium levels?

Accepted Answer

Calcitonin

Answer

Parathyroid hormone

Answer

1, 25-dihydroxycholecalciferol

Answer

Vitamin D

Question 5

Increased insulin is characterized by all of the following, except:

Accepted Answer

Increased Glucagon secretion

Answer

Hypoglycemia

Answer

Enhanced fatty acid synthesis

Answer

Increased Intracellular potassium

Question 6

What is the effect of cortisol on bone metabolism?

Accepted Answer

Decreased bone matrix

Answer

Increases calcium absorption

Answer

Stimulates osteoblast activity

Answer

Increased bone matrix

Question 7

Intake of exogenous steroids causes

Accepted Answer

Adrenal insufficiency

Answer

Prolonged glucocorticoid exposure

Answer

Catecholamine excess

Answer

Hyperaldosteronism

Question 8

In a person who has fasted for 5 days, all are seen except:

Accepted Answer

GH levels decreased

Answer

Immunoreactive insulin decreased

Answer

Glucose tolerance decreased

Answer

Free fatty acids (plasma) increased

Question 9

What is the primary mechanism by which corticosteroids affect calcium levels in the body?

Accepted Answer

Decreased absorption from gut

Answer

Increased excretion from kidney

Answer

No significant effect

Answer

Decreased plasma calcium level

Question 10

What is the effect of insulin administration on the respiratory quotient (RQ) in diabetes?

Accepted Answer

RQ decreases in Diabetes and increases with insulin administration.

Answer

RQ remains unchanged in Diabetes.

Answer

In diabetes, RQ increases with insulin administration.

Answer

RQ increases in Diabetes and decreases with insulin administration

Endocrinology — MCQs

Endocrinology — MCQs

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