Endocrinology Practice Questions

Q: Insulin secretion is decreased by:

Adrenaline. ***Adrenaline*** - **Adrenaline** (epinephrine) stimulates **alpha-2 adrenergic receptors** on pancreatic beta cells, which inhibits insulin secretion. - This mechanism is important during **stress** or **hypoglycemia** to prevent excessive insulin release and support glucose mobilization. *Vagal stimulation* - **Vagal stimulation** (parasympathetic nervous system) generally **increases** insulin secretion. - This effect is mediated by the release of **acetylcholine**, which acts on muscarinic receptors on beta cells. *Glucagon* - While glucagon's primary role is to **increase blood glucose**, it can also directly **stimulate insulin secretion** under certain physiological conditions. - This serves as a feedback loop to prevent excessive hyperglycemia following glucagon-mediated glucose release. *Glucose* - **Glucose** is the primary physiological stimulus for **insulin secretion**. - High blood glucose levels directly activate pancreatic beta cells, leading to insulin release to lower blood glucose.

Q: Due to fear which of the following hormones increases rapidly?

Epinephrine. ***Epinephrine*** - **Epinephrine**, also known as adrenaline, is a hormone and neurotransmitter involved in the **"fight or flight" response** to stress, fear, or excitement. - When faced with fear, the **adrenal medulla** releases epinephrine, leading to rapid physiological changes like increased heart rate, blood pressure, and energy availability to prepare the body for immediate action. *Growth hormones* - **Growth hormone (GH)** primarily regulates growth, metabolism, and body composition. - While stress can influence GH secretion, a rapid increase in direct response to acute fear is not its primary function. *Thyroid hormone* - **Thyroid hormones (T3 and T4)** regulate metabolism, energy balance, and body temperature over a longer term. - Their primary role is not in the immediate, rapid physiological response to acute fear. *Corticosteroid* - **Corticosteroids**, such as cortisol, are released in response to stress, but their increase is typically more prolonged than the instant surge of epinephrine. - They play a role in modulating immune response and metabolism during stress but are not responsible for the immediate "fight or flight" reactions.

Q: The primary action of leptin is:

To decrease food intake. ***To decrease food intake*** - **Leptin** is a hormone primarily produced by **adipocytes (fat cells)** that acts on the hypothalamus to signal satiety and reduce hunger. - Higher levels of leptin indicate ample energy stores, leading to a **decrease in food intake** and an increase in energy expenditure. *To increase food intake* - This is the opposite of leptin's primary action; instead, hormones like **ghrelin** are known to increase food intake. - Leptin's role is to regulate long-term energy balance by **reducing appetite**. *To increase gastric contraction* - **Gastric contractions** are primarily regulated by neural and other hormonal signals (e.g., motilin, gastrin), not leptin. - Leptin's main target is the central nervous system to influence overall **appetite control**. *To increase intestinal motility* - Intestinal motility is primarily influenced by the **enteric nervous system** and hormones such as **serotonin** and **motilin**. - Leptin's action is more focused on **central regulation of satiety** rather than direct effects on gut movement.

Q: Which of the following statements regarding prolactin levels is true?

Sleep - Increased prolactin. ***Sleep - Increased prolactin*** - Prolactin secretion is **pulsatile** and highest during **nocturnal sleep**, peaking around 4-5 AM. - This physiological increase occurs regardless of sleep onset and is a normal diurnal rhythm. *Hyperthyroidism - Increased prolactin* - **Hyperthyroidism** typically causes **decreased prolactin levels** due to altered dopaminergic tone and thyroid hormone effects on pituitary lactotrophs. - Conversely, **hypothyroidism**, particularly primary hypothyroidism, can lead to **increased prolactin** due to elevated TRH stimulating prolactin secretion. *Organic seizure - normal prolactin* - An **organic seizure** (e.g., tonic-clonic seizure) usually causes an **acute, significant elevation in prolactin** levels postictally. - This transient rise in prolactin can be a valuable diagnostic marker to differentiate epileptic seizures from non-epileptic events. *Psychogenic seizure - Decreased prolactin* - **Psychogenic non-epileptic seizures (PNES)** typically result in **normal or slightly decreased prolactin** levels after the event. - This is a key diagnostic differentiator from true epileptic seizures, which show postictal prolactin elevation.

Q: The function of which of the following is increased by an elevated parathyroid hormone concentration:

Osteoclasts. ***Osteoclasts*** - **Parathyroid hormone (PTH)** primarily acts to increase serum calcium levels by stimulating **osteoclasts**, leading to bone resorption and release of calcium and phosphate into the bloodstream. - While PTH does not directly act on osteoclasts, it binds to receptors on osteoblasts, which then release factors that activate osteoclasts. *Action of osteoblasts only* - PTH indirectly affects **osteoblasts** by binding to their receptors, but this action primarily leads to **RANKL expression**, which then stimulates osteoclast activity, not a direct increase in osteoblastic bone formation. - Chronic elevation of PTH, as seen in primary hyperparathyroidism, can paradoxically lead to a net loss of bone mass due to increased osteoclastic activity. *Phosphate reabsorptive pathways in the renal tubules* - PTH actually **decreases reabsorption of phosphate** in the renal tubules, leading to phosphaturia. This helps to prevent calcium-phosphate precipitation by lowering serum phosphate levels while raising calcium. - This is a key mechanism by which PTH increases serum calcium—by both mobilizing it from bone and reducing its renal excretion, while simultaneously promoting renal phosphate excretion. *Hepatic formation of 25-hydroxycholecalciferol* - The **liver** is responsible for the hydroxylation of vitamin D3 (cholecalciferol) to **25-hydroxycholecalciferol (calcidiol)**, a process that is not directly regulated by PTH. - PTH primarily stimulates the **kidneys** to convert 25-hydroxycholecalciferol to its active form, **1,25-dihydroxyvitamin D (calcitriol)**, which then enhances intestinal calcium absorption.

Q: Function of leptin is:

Reduce food intake. ***Reduce food intake*** - **Leptin** is a hormone secreted by **adipose tissue** that signals **satiety** to the brain, which leads to a reduction in energy intake and increased expenditure. - It acts on the **hypothalamus** to inhibit the production of neuropeptides that stimulate appetite and to stimulate the production of neuropeptides that suppress appetite. *Stimulation of AgRP* - **Agouti-related peptide (AgRP)** is a neuropeptide that **promotes feeding** and reduces energy expenditure. - Leptin's function is to **inhibit, not stimulate**, AgRP expression and activity, thus suppressing appetite. *Decrease lipolysis* - Leptin generally acts to **increase lipolysis** and lipid oxidation in peripheral tissues, rather than decrease it. - This action helps to reduce fat stores and increase energy expenditure, aligning with its role in weight regulation. *All of the options* - This option is incorrect because leptin's primary role is to **reduce food intake**, and it **inhibits AgRP** and generally **increases lipolysis**, contrary to the other choices. - Therefore, not all the listed functions are accurate descriptions of leptin's actions.

Q: Excessive production of aldosterone results in:

Depressed plasma renin. ***Depressed plasma renin*** - **Excessive aldosterone production** (primary hyperaldosteronism) independently leads to **sodium and water retention**, expanding extracellular fluid volume and consequently **suppressing renin secretion** via negative feedback. - While secondary hyperaldosteronism (e.g., due to renal artery stenosis) can involve high renin, primary aldosteronism is characterized by **low renin levels** because the adrenal glands are overproducing aldosterone autonomously. *Potassium retention* - Aldosterone's primary role in the kidney is to promote **sodium reabsorption** and **potassium excretion** in the principal cells of the collecting duct. - Therefore, excessive aldosterone typically leads to **hypokalemia** (low potassium levels) due to increased potassium loss, not retention. *Metabolic acidosis* - Aldosterone enhances the secretion of **hydrogen ions (H+)** in the intercalated cells of the collecting duct, helping to regulate acid-base balance. - Excessive aldosterone consequently leads to increased H+ excretion, which can result in **metabolic alkalosis**, not acidosis. *Severe hypotension* - Aldosterone promotes **sodium and water reabsorption**, leading to an increase in **blood volume** and **blood pressure**. - Therefore, excessive aldosterone production typically results in **hypertension** (high blood pressure), not hypotension.

Q: The arterial blood glucose concentration in normal humans after a meal is in the range of:

120 to 140 mg/dL. ***120 to 140 mg/dL*** - After a meal, **carbohydrates** are digested into glucose, which is absorbed into the bloodstream, causing a physiological rise in blood glucose levels. - This range represents the normal **postprandial (after meal)** peak glucose concentration in healthy individuals before insulin brings it back down. *30 to 50 mg/dL* - This range is significantly **lower than normal** and indicates severe **hypoglycemia**, which can lead to symptoms like confusion, seizures, and loss of consciousness. - Such low levels are not seen in healthy individuals after a meal. *50 to 70 mg/dL* - This range represents **mild to moderate hypoglycemia**, which can cause symptoms such as sweating, tremors, and hunger. - While lower than normal, it is still not the typical post-meal glucose level in healthy individuals. *220 to 250 mg/dL* - This range is significantly **higher than normal** and indicates **hyperglycemia**, suggesting impaired glucose regulation. - Such levels after a meal are often seen in individuals with **diabetes mellitus** or impaired glucose tolerance.

Q: Iodine uptake is seen in the following organ:

Thyroid. ***Thyroid*** - The **thyroid gland** actively traps **iodine** from the bloodstream using the **sodium-iodide symporter (NIS)** to synthesize thyroid hormones, **T3** and **T4**. - This high affinity for iodine is exploited in diagnostic imaging (e.g., **radioactive iodine uptake test**) and therapeutic applications (e.g., **radioactive iodine ablation** for thyroid cancer). *Parathyroid* - The **parathyroid glands** are primarily involved in regulating **calcium** and **phosphate** metabolism, producing **parathyroid hormone (PTH)**. - They do not have a significant mechanism for **iodine uptake** or utilization. *Ovary* - The **ovaries** are endocrine glands responsible for producing **estrogen** and **progesterone** and are involved in female reproduction. - They do not exhibit significant **iodine uptake** as they do not use iodine for their primary hormonal functions. *All of the options* - This option is incorrect because while the **thyroid** actively takes up iodine, the **parathyroid glands** and **ovaries** do not. - Only organs involved in **thyroid hormone synthesis** or with specific iodine-transporting mechanisms show significant iodine uptake.

Q: If blood supply to hypothalamus is interrupted through median eminence which hormone will have normal secretion?

Vasopressin. ***Vasopressin (ADH)*** - Vasopressin is synthesized in the **supraoptic and paraventricular nuclei** of the hypothalamus - It travels down **axons** (hypothalamic-hypophyseal tract) to the **posterior pituitary** where it is stored and released - Its secretion is **NOT dependent on the hypophyseal portal system** that passes through the median eminence - Interruption of the portal blood supply through the median eminence affects only the **anterior pituitary hormones** - Vasopressin secretion would remain **completely normal** as it bypasses the portal system entirely *Prolactin* - Prolactin is an anterior pituitary hormone under **tonic inhibition** by dopamine from the hypothalamus - Dopamine reaches the anterior pituitary via the **portal system through the median eminence** - Interruption of this blood supply would **block dopamine delivery**, resulting in **increased prolactin secretion** (not normal) - This is the classic "stalk effect" seen in pituitary stalk lesions *GH* - Growth Hormone requires **GHRH (Growth Hormone-Releasing Hormone)** stimulation from the hypothalamus - GHRH travels via the **portal system** to stimulate the anterior pituitary - Portal disruption prevents GHRH delivery → **Decreased GH secretion** *TSH* - Thyroid-Stimulating Hormone requires **TRH (Thyrotropin-Releasing Hormone)** stimulation - TRH travels via the **portal system** to the anterior pituitary - Portal disruption prevents TRH delivery → **Decreased TSH secretion**

Question 1

Insulin secretion is decreased by:

Accepted Answer

Adrenaline

Answer

Vagal stimulation

Answer

Glucagon

Answer

Glucose

Question 2

Due to fear which of the following hormones increases rapidly?

Accepted Answer

Epinephrine

Answer

Growth hormones

Answer

Thyroid hormone

Answer

Corticosteroid

Question 3

The primary action of leptin is:

Accepted Answer

To decrease food intake

Answer

To increase food intake

Answer

To increase gastric contraction

Answer

To increase intestinal motility

Question 4

Which of the following statements regarding prolactin levels is true?

Accepted Answer

Sleep - Increased prolactin

Answer

Hyperthyroidism - Increased prolactin

Answer

Organic seizure - normal prolactin

Answer

Psychogenic seizure - Normal prolactin

Question 5

The function of which of the following is increased by an elevated parathyroid hormone concentration:

Accepted Answer

Osteoclasts

Answer

Action of osteoblasts only

Answer

Phosphate reabsorptive pathways in the renal tubules

Answer

Hepatic formation of 25-hydroxycholecalciferol

Question 6

Function of leptin is:

Accepted Answer

Reduce food intake

Answer

Stimulation of AgRP

Answer

Decrease lipolysis

Answer

All of the options

Question 7

Excessive production of aldosterone results in:

Accepted Answer

Depressed plasma renin

Answer

Potassium retention

Answer

Metabolic acidosis

Answer

Severe hypotension

Question 8

The arterial blood glucose concentration in normal humans after a meal is in the range of:

Accepted Answer

120 to 140 mg/dL

Answer

30 to 50 mg/dL

Answer

50 to 70 mg/dL

Answer

220 to 250 mg/dL

Question 9

Iodine uptake is seen in the following organ:

Accepted Answer

Thyroid

Answer

Parathyroid

Answer

Ovary

Answer

All of the options

Question 10

If blood supply to hypothalamus is interrupted through median eminence which hormone will have normal secretion?

Accepted Answer

Vasopressin

Answer

GH

Answer

TSH

Answer

Prolactin

Endocrinology — MCQs

Endocrinology — MCQs

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