Endocrinology Practice Questions

Q: Insulin is essential for glucose entry in?

Muscle cells. ***Muscle cells*** - **Insulin** promotes glucose uptake into **muscle cells** by stimulating the translocation of **GLUT4 transporters** to the cell surface. - In the absence of insulin, **glucose uptake** into quiescent muscle cells is significantly reduced. *Cortical neurons* - **Neurons** in the brain, including cortical neurons, primarily utilize **GLUT1** and **GLUT3 transporters** for glucose uptake, which are **insulin-independent**. - This ensures a constant supply of glucose to the brain, even during periods of low insulin. *Beta cells of pancreas* - **Pancreatic beta cells** use **GLUT2 transporters** for glucose uptake, which are **insulin-independent** and have a high capacity. - This allows beta cells to sense glucose levels and regulate insulin secretion accordingly. *Renal tubular cells* - **Renal tubular cells** reabsorb glucose primarily through **sodium-glucose co-transporters (SGLTs)** and **GLUT2 transporters**, both of which are **insulin-independent**. - Their primary role is in maintaining glucose homeostasis by preventing glucose loss in urine.

Q: Which of the following hormones is secreted by acidophils in the anterior pituitary gland?

GH. ***GH*** - **Growth Hormone (GH)** is secreted by **somatotrophs**, which are a type of acidophil cell in the anterior pituitary. - GH plays a crucial role in **growth**, **metabolism**, and cell reproduction. - **Note**: Prolactin is also secreted by acidophils (lactotrophs), but among the given options, only GH is an acidophil hormone. *TSH* - **Thyroid-stimulating hormone (TSH)** is secreted by **thyrotrophs**, which are **basophil** cells in the anterior pituitary. - TSH stimulates the **thyroid gland** to produce thyroid hormones. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is secreted by **corticotrophs**, which are another type of **basophil** cell. - ACTH stimulates the **adrenal cortex** to secrete glucocorticoids. *FSH* - **Follicle-stimulating hormone (FSH)** is secreted by **gonadotrophs**, which are also **basophil** cells. - FSH is involved in the **development of follicles** in the ovaries and **spermatogenesis** in the testes.

Q: Which of the following statements about ghrelin is false?

Directly regulates thyroid hormone secretion. ***Directly regulates thyroid hormone secretion*** - **Ghrelin** does NOT directly regulate **thyroid hormone secretion** or the **hypothalamic-pituitary-thyroid (HPT) axis**. - Ghrelin's primary physiological roles are related to **appetite stimulation**, **growth hormone release**, and **energy balance**. - While there may be indirect metabolic interactions, ghrelin has no established direct regulatory role in **TSH** or **thyroid hormone** production. *Produced by stomach cells* - This statement is **true**; **ghrelin** is predominantly produced by **P/D1 cells** (also called X/A-like cells) in the **fundus of the stomach**. - These cells release ghrelin primarily when the stomach is empty, signaling hunger to the brain. *Stimulates appetite* - This statement is **true**; ghrelin is often referred to as the "**hunger hormone**" because it acts on the **arcuate nucleus** of the **hypothalamus** to increase food intake. - Its levels rise before meals and decrease after eating, playing a crucial role in the **short-term regulation of appetite**. *Stimulates growth* - This statement is **true**; **ghrelin** is a potent stimulator of **growth hormone (GH) release** from the **anterior pituitary gland**. - It acts on **growth hormone secretagogue receptors (GHS-R)** on **somatotrophs** to promote GH secretion, contributing to its role in **growth** and **metabolism**.

Q: The primary site of vasopressin synthesis is

Supraoptic nucleus. ***Supraoptic nucleus*** - The **supraoptic nucleus** of the hypothalamus is the **primary site** for the synthesis of **vasopressin** (also known as antidiuretic hormone or ADH). - Approximately **80% of vasopressin** is produced by the neurosecretory cells in this nucleus. - The synthesized vasopressin is transported down axons to the posterior pituitary for storage and release. *Preoptic nucleus* - The **preoptic nucleus** is involved in various homeostatic functions, including **thermoregulation** and **sleep regulation**, but not the synthesis of vasopressin. - While it has neuronal connections to the hypothalamus, it does not produce ADH. *Paraventricular nucleus* - The **paraventricular nucleus** also synthesizes **both vasopressin and oxytocin**, accounting for approximately **20% of vasopressin production**. - While it does produce vasopressin, the **supraoptic nucleus remains the primary site**, making it the correct answer to this question. - The PVN also plays important roles in stress response and various autonomic functions. *Posterior pituitary* - The **posterior pituitary** (neurohypophysis) is responsible for the **storage and release** of vasopressin and oxytocin, not their synthesis. - These hormones are produced in the hypothalamic nuclei (supraoptic and paraventricular) and then transported down axonal tracts to the posterior pituitary.

Q: How does adrenaline affect insulin secretion?

Inhibition of beta cells. ***Inhibition of beta cells*** - **Adrenaline** (epinephrine) binds to **alpha-2 adrenergic receptors** on pancreatic beta cells, which are coupled to inhibitory G-proteins. - This binding leads to **decreased cAMP levels** and hyperpolarization of the beta cell membrane, ultimately inhibiting insulin release. *Stimulation of delta cells* - **Delta cells** produce **somatostatin**, which generally inhibits the secretion of insulin and glucagon. - While adrenaline can have various systemic effects, its primary direct action on insulin secretion is not through stimulating delta cells. *Stimulation of g cells* - **G cells** in the stomach produce **gastrin**, a hormone involved in gastric acid secretion. - Adrenaline's primary physiological role in glucose metabolism does not involve direct stimulation of G cells to influence insulin secretion. *Stimulation of beta cells* - **Stimulation of beta cells** would lead to increased insulin secretion. - Adrenaline's physiological role, particularly in **stress responses**, is to raise blood glucose, which is achieved in part by **reducing insulin availability** to ensure glucose enters the bloodstream rather than tissues.

Q: Growth hormone level is highest during

Sleep. ***Sleep*** - Growth hormone (GH) secretion is **pulsatile**, with the largest and most consistent pulses occurring during **slow-wave sleep** (deep sleep). - This nocturnal surge contributes significantly to the overall daily GH output and is crucial for growth and metabolic regulation. *Hypoglycemia* - While **hypoglycemia** is a potent stimulus for GH release, it is an acute stress response rather than a state where GH levels are consistently highest. - The body's primary response to hypoglycemia is to raise blood glucose, and while GH helps, it is not the peak physiological secretion time. *Fasting* - **Prolonged fasting** can increase GH secretion as a mechanism to mobilize fat stores and conserve glucose. - However, the peak levels due to fasting are generally less pronounced than the dramatic surge observed during deep sleep. *Exercise* - **Vigorous exercise** can acutely stimulate GH release, particularly with sustained effort. - This increase is typically transient and not as high or consistently cyclical as the secretion during nocturnal sleep.

Q: For how long is Thyroxine stored in the thyroid follicle?

2-3 months. ***2-3 months*** - The thyroid gland stores a substantial amount of **thyroglobulin**, a precursor to **thyroid hormones**, within the **follicular lumen**. - This large storage capacity ensures a **reserve of hormones** sufficient for approximately **2 to 3 months** of normal physiological needs, even if thyroid hormone synthesis were to cease. *1-2 weeks* - This duration is too short for the thyroid's actual storage capacity; the gland is designed for a much longer reserve of **thyroid hormones**. - A 1-2 week supply would make the body highly vulnerable to **rapid onset of hypothyroidism** if synthesis were disrupted. *1-2 days* - This period is extremely short and does not reflect the significant storage capabilities of the thyroid gland, which is unique among endocrine glands for its large **extracellular storage** of hormones. - Such a limited reserve would lead to immediate and severe **hypothyroidism** with any interruption in hormone production. *3-4 years* - While the thyroid does store a considerable amount of hormone, a 3-4 year supply is an **overestimation of its storage capacity**. - The metabolic turnover and requirements of the body for thyroid hormones necessitate replenishment within a few months, rather than years.

Q: Which of the following is NOT true about ghrelin?

Has anorexic effect. ***Has anorexic effect*** - Ghrelin is known as the **"hunger hormone"** because it stimulates appetite and has an **orexigenic effect**, meaning it increases food intake. - Therefore, stating that it has an **anorexic effect** (reduces appetite) is incorrect. *Stimulates growth hormone release* - Ghrelin is a **natural ligand** for the **growth hormone secretagogue receptor (GHSR)**. - This binding leads to the stimulation of **growth hormone (GH)** release from the pituitary gland. *Secreted by gastric fundus cells* - The primary source of ghrelin in the body is the **P/D1 cells** found in the mucosa of the **gastric fundus**. - Smaller amounts are also produced in the small intestine, pancreas, and hypothalamus. *Increases gastric motility* - Ghrelin is involved in regulating stomach function and can **increase gastric motility** and acid secretion. - This action helps to prepare the digestive system for incoming food.

Q: Laron dwarfism is due to:

GH receptor resistance. ***GH receptor resistance*** - **Laron dwarfism** is caused by a genetic defect in the **growth hormone (GH) receptor**, leading to cellular insensitivity to GH. - Despite normal or elevated GH levels, the body cannot respond to GH, resulting in impaired **insulin-like growth factor 1 (IGF-1)** production and stunted growth. *GH deficiency* - This would involve insufficient production of **growth hormone** from the pituitary gland. - In such cases, administration of exogenous GH would typically be effective, which is not the case in Laron dwarfism due to receptor resistance. *GHRH deficiency* - A deficiency in **growth hormone-releasing hormone (GHRH)** from the hypothalamus would lead to decreased GH secretion. - This would ultimately result in **GH deficiency**, but the primary defect in Laron syndrome is at the receptor level, not in GHRH or GH production. *IGF-1 deficiency* - While Laron dwarfism does result in functionally low **IGF-1** levels due to GH insensitivity, the primary defect is in the GH receptor, which *prevents* GH from stimulating IGF-1 production. - True primary **IGF-1 deficiency** (apart from GH resistance) is a less common cause of dwarfism and would not involve high GH levels.

Q: All of the following are actions of cortisol EXCEPT:

Decrease blood amino acid. ***Decrease blood amino acid*** - This is **NOT** an action of cortisol, making it the correct answer for this EXCEPT question. - Cortisol actually **increases** blood amino acids through **protein catabolism** in muscle and other peripheral tissues. - The catabolic effect mobilizes amino acids from structural proteins, **elevating blood amino acid levels** during stress. *Increase blood amino acid* - This **IS** a correct action of cortisol through **protein breakdown** in peripheral tissues. - Cortisol promotes proteolysis in muscle, releasing amino acids into circulation for use in gluconeogenesis and acute phase protein synthesis. *Increase liver amino acid* - This **IS** a correct action of cortisol as it promotes **hepatic uptake** of amino acids from the bloodstream. - These amino acids are utilized for **gluconeogenesis** and synthesis of plasma proteins in the liver. *Decrease liver amino acid* - This could be considered an action in the sense that cortisol promotes rapid **utilization** of amino acids for gluconeogenesis. - However, the net effect is increased amino acid **flux through** the liver rather than a decrease in availability, as cortisol simultaneously increases hepatic uptake.

Question 1

Insulin is essential for glucose entry in?

Accepted Answer

Muscle cells

Answer

Beta cells of pancreas

Answer

Cortical neurons

Answer

Renal tubular cells

Question 2

Which of the following hormones is secreted by acidophils in the anterior pituitary gland?

Accepted Answer

GH

Answer

TSH

Answer

ACTH

Answer

FSH

Question 3

Which of the following statements about ghrelin is false?

Accepted Answer

Directly regulates thyroid hormone secretion

Answer

Stimulates appetite

Answer

Stimulates growth

Answer

Produced by stomach cells

Question 4

The primary site of vasopressin synthesis is

Accepted Answer

Supraoptic nucleus

Answer

Preoptic nucleus

Answer

Paraventricular nucleus

Answer

Posterior pituitary

Question 5

How does adrenaline affect insulin secretion?

Accepted Answer

Inhibition of beta cells

Answer

Stimulation of delta cells

Answer

Stimulation of G cells

Answer

Stimulation of beta cells

Question 6

Growth hormone level is highest during

Accepted Answer

Sleep

Answer

Hypoglycemia

Answer

Fasting

Answer

Exercise

Question 7

For how long is Thyroxine stored in the thyroid follicle?

Accepted Answer

2-3 months

Answer

1-2 weeks

Answer

1-2 days

Answer

3-4 years

Question 8

Which of the following is NOT true about ghrelin?

Accepted Answer

Has anorexic effect

Answer

Stimulates growth hormone release

Answer

Secreted by gastric fundus cells

Answer

Increases gastric motility

Question 9

Laron dwarfism is due to:

Accepted Answer

GH receptor resistance

Answer

GH deficiency

Answer

GHRH deficiency

Answer

IGF-1 deficiency

Question 10

All of the following are actions of cortisol EXCEPT:

Accepted Answer

Decrease blood amino acid

Answer

Increase blood amino acid

Answer

Increase liver amino acid

Answer

Decrease liver amino acid

Endocrinology — MCQs

Endocrinology — MCQs

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