Endocrinology Practice Questions

Q: Insulin secretion is induced by following EXCEPT:

Somatostatin. ***Somatostatin*** - **Somatostatin** directly inhibits insulin secretion from pancreatic beta cells, acting as a paracrine regulator to modulate islet hormone release. - It binds to **somatostatin receptors (SSTRs)** on beta cells, leading to a reduction in cAMP and inhibition of voltage-gated calcium channels, thereby decreasing insulin exocytosis. *Estrogens* - **Estrogens** generally enhance insulin secretion and improve insulin sensitivity, especially during pregnancy or in response to high glucose levels. - They can increase **beta-cell mass** and survival, contributing to better glycemic control. *Growth hormone* - **Growth hormone (GH)** can indirectly induce insulin secretion by promoting insulin resistance, which necessitates increased insulin production to maintain normal glucose levels. - Chronically elevated GH, as seen in **acromegaly**, often leads to hyperinsulinemia and can even cause diabetes. *Placental lactogen* - **Human placental lactogen (hPL)** is a hormone produced during pregnancy that primarily increases maternal insulin resistance to ensure adequate glucose supply to the fetus. - This increased resistance compensatorily stimulates **maternal beta cells** to secrete more insulin, leading to hyperinsulinemia.

Q: True about Parathyroid hormone:

Stimulates 1,25-D3 formation. ***Stimulate 1, 25 D3 formation*** - Parathyroid hormone (PTH) stimulates the kidneys to convert **25-hydroxyvitamin D** to its active form, **1,25-dihydroxyvitamin D (calcitriol)**. - **Calcitriol** is essential for increasing calcium absorption from the intestines. *Inhibits Ca2+ absorption from the intestines* - This statement is **incorrect**; PTH directly and indirectly (via calcitriol) promotes **calcium absorption** from the intestines. - **PTH's primary role** is to *increase* plasma calcium levels, which includes enhancing intestinal absorption. *It is steroidal in nature* - This statement is **incorrect**; Parathyroid hormone is a **peptide hormone**, not a steroidal hormone. - Steroidal hormones are derived from **cholesterol** (e.g., cortisol, estrogen), while peptide hormones are chains of amino acids. *All of the options* - This option is incorrect because the other two statements regarding PTH's action are demonstrably **false**.

Q: Stress hyperglycemia occurs due to all except -

Decreased level of norepinephrine. ***Decreased level of norepinephrine*** - **Norepinephrine** is a **catecholamine** that generally **increases blood glucose** by stimulating **glycogenolysis** and **gluconeogenesis**. - Therefore, a *decrease* in norepinephrine would *reduce* stress-induced hyperglycemia, making this the exception. *Increased level of ACTH* - **ACTH (Adrenocorticotropic Hormone)** stimulates the adrenal glands to release **cortisol**, which contributes significantly to stress hyperglycemia. - Increased ACTH levels therefore *promote* hyperglycemia in stress. *Insulin resistance* - **Insulin resistance** is a common feature during stress, where target cells become less responsive to insulin's effects. - This reduced insulin sensitivity leads to higher circulating glucose levels, contributing to hyperglycemia. *Increased level of cortisol* - **Cortisol** is a key **stress hormone** that promotes **gluconeogenesis** (production of glucose from non-carbohydrate sources) and **glycogenolysis** (breakdown of glycogen to glucose). - Elevated cortisol levels directly lead to an increase in blood glucose, causing hyperglycemia.

Q: Thyroid peroxidase will help in all the following except:

Iodide trapping. ***Iodide trapping*** - **Iodide trapping** is the correct answer as it is **NOT** a function of thyroid peroxidase (TPO). - **Iodide trapping** (or iodide pump) is the active transport of iodide into thyroid follicular cells, mediated by the **sodium-iodide symporter (NIS)**, a completely separate protein system. - This process concentrates iodide within the thyroid gland, which is essential before TPO can act. *Iodide to iodine* - **Thyroid peroxidase (TPO) DOES** catalyze the **oxidation of iodide (I-) to iodine (I2)** at the apical membrane. - This is one of the primary enzymatic functions of TPO, making this option incorrect for an "EXCEPT" question. *Secretion of thyroglobulin into colloid* - **Thyroglobulin (Tg)** is secreted into the colloid by **exocytosis**, not directly by TPO. - However, TPO is located at the apical membrane and **facilitates the iodination of thyroglobulin** that has been secreted into the colloid. - While TPO doesn't perform the secretion itself, it has a direct functional relationship with thyroglobulin in the colloid, unlike iodide trapping which is entirely separate from TPO function. *Binding thyroglobulin* - **Thyroid peroxidase (TPO) DOES** interact with and act upon **thyroglobulin** as its substrate. - TPO catalyzes the iodination of tyrosine residues on the thyroglobulin molecule to form **monoiodotyrosine (MIT)** and **diiodotyrosine (DIT)**, and subsequently couples these to form T3 and T4.

Q: In which of the following forms the Anti diuretic hormone (ADH) is circulated in plasma:

Free form. ***Correct: Free form*** - **ADH circulates in plasma predominantly in its free (unbound) form** to reach target tissues and bind to its receptors (V1 and V2 receptors). - Upon secretion from the posterior pituitary into the bloodstream, **ADH dissociates from neurophysin-II** and circulates freely in plasma. - The free form has a short plasma half-life of **5-20 minutes** and is the active form that exerts physiological effects on kidneys, blood vessels, and other target organs. - Only free hormone can bind to receptors; bound forms are inactive. *Incorrect: Bound to neurophysin-II* - **Neurophysin-II serves as a carrier protein during intracellular transport**, not plasma circulation. - It transports ADH from the hypothalamus (supraoptic and paraventricular nuclei) down the axons to the posterior pituitary for storage. - While co-secreted with ADH, **neurophysin-II and ADH rapidly dissociate upon release into plasma**. - This option confuses the transport/storage mechanism with the circulation form. *Incorrect: Bound to neurophysin-I* - **Neurophysin-I** is the specific carrier protein for **oxytocin**, not ADH. - It facilitates intracellular transport of oxytocin from hypothalamus to posterior pituitary. - ADH does not bind to neurophysin-I. *Incorrect: Bound to plasma albumin* - **Albumin** is a non-specific carrier protein for various lipophilic hormones (thyroid hormones, steroid hormones). - **ADH is a peptide hormone** that does not require albumin for transport or solubility. - ADH circulates freely in aqueous plasma without significant protein binding.

Q: Decreased calcium levels lead to

Increased parathormone. ***Increased parathormone*** * **Hypocalcemia** is the **direct and primary stimulus** for the release of **parathyroid hormone (PTH)** from the parathyroid glands. * This is an **immediate physiological response** - calcium-sensing receptors on parathyroid cells directly detect low calcium and trigger PTH secretion. * PTH then acts to restore serum calcium levels by increasing bone resorption, renal reabsorption of calcium, and stimulating **calcitriol** synthesis. *Increased 24,25 dihydroxycholecalciferol* * **24,25-dihydroxycholecalciferol** is an inactive metabolite of vitamin D, produced when vitamin D levels are sufficient or high. * Its production is **downregulated** in hypocalcemia, as the body prioritizes conversion to active vitamin D (calcitriol) rather than inactive metabolites. *Increased 1,25 dihydroxycholecalciferol* * While **1,25-dihydroxycholecalciferol (calcitriol)** does increase in response to hypocalcemia, this is an **indirect, secondary response** mediated through PTH, not a direct effect of low calcium. * The pathway: Decreased calcium → **PTH release (direct)** → PTH stimulates renal 1α-hydroxylase → increased calcitriol synthesis (indirect). * The question asks what decreased calcium "leads to" - the most accurate answer is the **direct, immediate response** (PTH), not downstream secondary effects. *Decreased calcitonin* * **Calcitonin** is a hormone that *lowers* blood calcium levels, primarily by inhibiting osteoclast activity and increasing renal calcium excretion. * Its secretion is stimulated by **high serum calcium levels**, so in hypocalcemia, calcitonin secretion decreases due to absence of the stimulus. * However, this is a **passive response** (lack of stimulation) rather than an active compensatory mechanism like PTH release.

Q: A major causal factor in some cases of hypogonadism is:

Reduced secretion of gonadotropin-releasing hormone (GnRH). ***Reduced secretion of gonadotropin-releasing hormone (GnRH)*** - **Hypogonadotropic hypogonadism** is characterized by low levels of LH and FSH due to inadequate GnRH secretion from the hypothalamus, leading to decreased testosterone production. - This can be caused by various factors, including genetic conditions, hypothalamic tumors, or functional suppression from stress or severe illness. *Excess secretion of testicular activin by Sertoli cells* - **Activin** promotes FSH synthesis and secretion from the pituitary but is not a primary cause of hypogonadism. - While disruptions in activin/inhibin balance can affect spermatogenesis, it doesn't directly cause a systemic hypogonadal state through its direct effect on GnRH or gonadal function. *Hypersecretion of pituitary LH and FSH as the result of increased GnRH* - **Hypersecretion of LH and FSH** in response to increased GnRH would lead to **hypergonadism**, or at least eugonadism, not hypogonadism. - This scenario would stimulate excessive testosterone production, the opposite of hypogonadism. *Failure of the hypothalamus to respond to testosterone* - The hypothalamus, as well as the pituitary, are sensitive to **negative feedback from testosterone** to regulate GnRH and gonadotropin release. - A failure to respond to testosterone would typically lead to **increased GnRH and gonadotropin secretion** (as the feedback loop is broken), resulting in higher testosterone levels, which contradicts hypogonadism.

Q: What is the percentage of T4 and T3 released from the thyroid gland?

90% T4; 10% T3. ***90% T4; 10% T3*** - The thyroid gland primarily secretes **thyroxine (T4)**, which accounts for approximately **90% of its total hormone output**. - **Triiodothyronine (T3)** is released in smaller amounts, making up approximately **10% of direct thyroid secretion**. - The majority of circulating T3 (about 80%) is derived from **peripheral deiodination of T4** in tissues like liver and kidneys, not from direct thyroid secretion. *80% T4; 20% T3* - This ratio **overestimates** the direct secretion of T3 from the thyroid gland. - While some older sources cite this ratio, the more widely accepted current value is **90:10**. - The higher circulating T3 levels seen in the body are due to **peripheral conversion**, not direct glandular secretion. *50% T4; 50% T3* - This ratio is incorrect as **T4 is the predominant hormone** released directly from the thyroid gland. - Equal secretion would not align with the thyroid's primary role as a **T4-producing gland** with T4 serving as a prohormone. *25% T4; 75% T3* - This ratio is completely incorrect and would reverse the actual secretory pattern. - **T4 is quantitatively the dominant hormone** secreted by the thyroid, with T3 playing a more active role after peripheral conversion.

Q: Which of the following hormones is released from the posterior pituitary?

Antidiuretic hormone. ***Antidiuretic hormone*** - The **posterior pituitary** (neurohypophysis) stores and releases **antidiuretic hormone (ADH)** and oxytocin. - ADH, also known as **vasopressin**, is synthesized in the **hypothalamus** and transported to the posterior pituitary for release. *Luteinizing hormone* - **Luteinizing hormone (LH)** is released from the **anterior pituitary** in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus. - LH plays a crucial role in **reproduction**, triggering ovulation in females and testosterone production in males. *Growth hormone* - **Growth hormone (GH)** is synthesized and secreted by the **anterior pituitary gland**. - Its release is regulated by **growth hormone-releasing hormone (GHRH)** and **somatostatin** from the hypothalamus. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is produced and secreted by the **anterior pituitary gland**. - ACTH stimulates the **adrenal cortex** to release cortisol, regulating stress responses and metabolism.

Q: All of these cause hyperglycemia except:

Insulin. ***Insulin*** - Insulin's primary function is to **lower blood glucose levels** by facilitating glucose uptake into cells and promoting glycogen synthesis. - It counters the effects of hormones that elevate blood sugar, directly leading to a **decrease in hyperglycemia**. *Catecholamines* - **Catecholamines** (e.g., epinephrine, norepinephrine) increase blood glucose by promoting **glycogenolysis** and **gluconeogenesis**. - They also **inhibit insulin secretion**, further contributing to elevated blood sugar. *Cortisol* - **Cortisol** is a **glucocorticoid** that raises blood glucose by increasing **gluconeogenesis** and reducing peripheral **glucose utilization**. - It can also decrease insulin sensitivity, leading to **hyperglycemia**. *GH* - **Growth hormone (GH)** can induce **insulin resistance** in peripheral tissues, which leads to reduced glucose uptake. - It also promotes **gluconeogenesis**, both contributing to elevated blood glucose levels.

Question 1

Insulin secretion is induced by following EXCEPT:

Accepted Answer

Somatostatin

Answer

Estrogens

Answer

Growth hormone

Answer

Placental lactogen

Question 2

True about Parathyroid hormone:

Accepted Answer

Stimulates 1,25-D3 formation

Answer

Inhibits Ca2+ absorption from the intestines

Answer

It is steroidal in nature

Answer

All of the options

Question 3

Stress hyperglycemia occurs due to all except -

Accepted Answer

Decreased level of norepinephrine

Answer

Increased level of ACTH

Answer

Insulin resistance

Answer

Increased level of cortisol

Question 4

Thyroid peroxidase will help in all the following except:

Accepted Answer

Iodide trapping

Answer

Iodide to iodine

Answer

Secretion of thyroglobulin into colloid

Answer

Binding thyroglobulin

Question 5

In which of the following forms the Anti diuretic hormone (ADH) is circulated in plasma:

Accepted Answer

Free form

Answer

Bound to neurophysin-I

Answer

Bound to neurophysin-II

Answer

Bound to plasma albumin

Question 6

Decreased calcium levels lead to

Accepted Answer

Increased parathormone

Answer

Increased 24,25 dihydroxycholecalciferol

Answer

Increased 1,25 dihydroxycholecalciferol

Answer

Decreased calcitonin

Question 7

A major causal factor in some cases of hypogonadism is:

Accepted Answer

Reduced secretion of gonadotropin-releasing hormone (GnRH)

Answer

Excess secretion of testicular activin by Sertoli cells

Answer

Hypersecretion of pituitary LH and FSH as the result of increased GnRH

Answer

Failure of the hypothalamus to respond to testosterone

Question 8

What is the percentage of T4 and T3 released from the thyroid gland?

Accepted Answer

90% T4; 10% T3

Answer

50% T4; 50% T3

Answer

80% T4; 20% T3

Answer

25% T4; 75% T3

Question 9

Which of the following hormones is released from the posterior pituitary?

Accepted Answer

Antidiuretic hormone

Answer

Luteinizing hormone

Answer

Growth hormone

Answer

ACTH

Question 10

All of these cause hyperglycemia except:

Accepted Answer

Insulin

Answer

Catecholamines

Answer

Cortisol

Answer

GH

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?