Assessment of Endocrine Function — MCQs

10 questions

A patient presents with large sweaty hands, macroglossia, and frontal bossing. What is the best test for confirmation of the diagnosis?

The most important regulator of serum 1,25(OH)2 vitamin D concentration is:

Which among the following is the best method to assess adequacy of fluid resuscitation in a polytrauma patient?

All the following hormones have receptors on the plasma membrane of target tissues except:

Insulin-like growth factor is secreted by:

Wolf Chaikoff effect:

Which hormone is released when serum calcium levels decrease?

All of the following are known functions of hypothalamus except

At the time point indicated by the arrow, the hormone levels are:

Q10

A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?

Assessment of Endocrine Function Indian Medical PG Practice Questions and MCQs

Question 1: A patient presents with large sweaty hands, macroglossia, and frontal bossing. What is the best test for confirmation of the diagnosis?

A. GHRH levels
B. IGF-1 (Correct Answer)
C. IGF-2
D. GH levels after glucose suppression
E. Random GH level

Explanation: ***IGF-1*** - Elevated **IGF-1 (Insulin-like Growth Factor 1)** is the most reliable screening test for acromegaly, reflecting integrated GH secretion over time. - The clinical signs of **large sweaty hands**, **macroglossia**, and **frontal bossing** are classic symptoms of acromegaly, caused by excessive growth hormone (GH) production, which then stimulates IGF-1. *GHRH levels* - **Growth hormone-releasing hormone (GHRH)** levels are typically only measured when investigating ectopic GHRH production as a rare cause of acromegaly, which is not the primary diagnostic step. - While GHRH stimulates GH, its direct measurement is not the standard initial diagnostic test for suspected pituitary-driven acromegaly. *IGF-2* - **IGF-2 (Insulin-like Growth Factor 2)** plays a role in fetal growth and certain tumor-related syndromes, but it is not the primary mediator or diagnostic marker for acromegaly in adults. - IGF-1, not IGF-2, is the main growth factor responsible for the anabolic effects of growth hormone. *GH levels after glucose suppression* - Measuring **GH levels after glucose suppression** (oral glucose tolerance test with 75g glucose) is a confirmatory test for acromegaly, used when IGF-1 levels are equivocal or borderline. - In healthy individuals, glucose suppresses GH secretion to <1 ng/mL, but in acromegaly, GH levels remain elevated (failure to suppress), confirming autonomous GH hypersecretion. *Random GH level* - **Random GH levels** are unreliable for diagnosing acromegaly due to the pulsatile nature of GH secretion, with significant variation throughout the day. - A single normal GH level does not exclude acromegaly, and a single elevated level can occur in healthy individuals during normal secretory peaks, making it inadequate as a diagnostic test.

Question 2: The most important regulator of serum 1,25(OH)2 vitamin D concentration is:

A. Calcium levels in serum
B. Magnesium levels in serum
C. Parathyroid hormone (Correct Answer)
D. 25-hydroxyvitamin D in serum

Explanation: ***Parathyroid hormone*** - **Parathyroid hormone (PTH)** directly stimulates the **kidney's 1-alpha hydroxylase** enzyme, which converts **25(OH)D** to its active form, **1,25(OH)2D (calcitriol)**. - This regulation is critical for maintaining **calcium and phosphate homeostasis**, with PTH levels increasing when serum calcium is low, thereby boosting 1,25(OH)2D production. *Calcium levels in serum* - While **low serum calcium** indirectly stimulates **PTH** release, which then regulates 1,25(OH)2 vitamin D, calcium itself is not the direct or most important regulator. - The direct regulatory action on the conversion enzyme is mediated by PTH. *Magnesium levels in serum* - **Magnesium** plays a cofactor role in various enzymatic reactions, including those involving vitamin D metabolism, but it is not a direct or primary regulator of **1,25(OH)2 vitamin D concentration**. - Severe **hypomagnesemia** can sometimes impair PTH secretion and action, indirectly affecting vitamin D, but this is a secondary effect. *25-hydroxyvitamin D in serum* - **25-hydroxyvitamin D** is the precursor to **1,25(OH)2 vitamin D**, and its availability limits the maximum potential production of the active form. - However, the *rate* of conversion into the active form and thus the *concentration* of 1,25(OH)2D is primarily dictated by PTH, not the precursor itself.

Question 3: Which among the following is the best method to assess adequacy of fluid resuscitation in a polytrauma patient?

A. BP
B. CVP
C. Urine output (Correct Answer)
D. Pulse

Explanation: ***Urine output*** - **Urine output** is a direct and reliable indicator of **renal perfusion** and overall **volume status**, reflecting effective **systemic circulation** in a polytrauma patient. - Consistent hourly urine output (e.g., >0.5 mL/kg/hr in adults) suggests adequate fluid resuscitation and organ perfusion, particularly the kidneys. *BP* - **Blood pressure (BP)** can be maintained within normal limits by compensatory mechanisms even during significant **hypovolemia**, making it an unreliable early indicator of fluid status. - BP can also be affected by pain, stress, or medications, making its interpretation in isolation challenging in polytrauma. *CVP* - **Central venous pressure (CVP)** is a measure of preload but can be influenced by multiple factors such as **intrathoracic pressure**, **ventilator settings**, and **cardiac function**, making its accuracy in assessing fluid status debatable in trauma. - CVP measurements might also be elevated in patients with **cardiac contusions** or pre-existing **cardiac conditions**, leading to misinterpretation of fluid needs. *Pulse* - **Pulse rate** is an early indicator of hypovolemia (tachycardia) but is highly sensitive to other factors such as pain, anxiety, and medications, limiting its specificity as a sole measure of fluid status. - In a polytrauma patient, an elevated pulse could be due to pain, stress, or other injuries, not solely reflecting inadequate fluid intake.

Question 4: All the following hormones have receptors on the plasma membrane of target tissues except:

A. Epinephrine
B. Glucagon
C. Estradiol (Correct Answer)
D. Thyrotropin

Explanation: ***Estradiol*** - **Estradiol** is a **steroid hormone** derived from cholesterol, making it **lipid-soluble**. - Due to its lipid solubility, estradiol can readily pass through the **plasma membrane** and bind to **intracellular receptors** in the cytoplasm or nucleus. *Epinephrine* - **Epinephrine** is a **catecholamine hormone** and is **water-soluble**. - Water-soluble hormones cannot cross the lipid bilayer of the plasma membrane and thus bind to **receptors located on the cell surface**. *Glucagon* - **Glucagon** is a **peptide hormone** and is **water-soluble**. - Like other peptide hormones, it binds to **specific receptors embedded in the plasma membrane** to elicit its cellular effects via second messenger systems. *Thyrotropin* - **Thyrotropin**, also known as **Thyroid-Stimulating Hormone (TSH)**, is a **glycoprotein hormone** and is **water-soluble**. - TSH exerts its action by binding to **receptors on the plasma membrane** of thyroid follicular cells.

Question 5: Insulin-like growth factor is secreted by:

A. Liver (Correct Answer)
B. Pituitary gland
C. Pancreas
D. Adrenal glands

Explanation: ***Liver*** - The **liver** is the primary site of **insulin-like growth factor 1 (IGF-1)** production in response to **growth hormone (GH)** stimulation. - IGF-1 mediates many of the growth-promoting effects of GH, affecting various tissues throughout the body. *Pituitary gland* - The **pituitary gland** secretes **growth hormone (GH)**, which then stimulates the liver to produce IGF-1, but it does not directly secrete IGF-1. - Its role is upstream in the GH-IGF-1 axis, initiating the signaling cascade. *Pancreas* - The **pancreas** is primarily known for secreting **insulin** and **glucagon**, which regulate blood glucose levels. - It does not produce significant amounts of IGF-1. *Adrenal glands* - The **adrenal glands** produce hormones like **cortisol**, **aldosterone**, and **androgens**. - They are not involved in the direct secretion of IGF-1.

Question 6: Wolf Chaikoff effect:

A. Iodine induced hyperthyroidism
B. Drug induced hyperthyroidism
C. Iodine induced hypothyroidism (Correct Answer)
D. Thyrotoxicosis due to excessive amount of thyroid hormone ingestion

Explanation: ***Iodine induced hypothyroidism*** - The **Wolf-Chaikoff effect** describes the phenomenon where a high concentration of **iodide** temporarily inhibits the synthesis and release of thyroid hormones. - This transient effect leads to a short period of **hypothyroidism** in response to excess iodine. *Iodine induced hyperthyroidism* - This describes **Jod-Basedow phenomenon**, which is distinct from the Wolf-Chaikoff effect. - **Jod-Basedow** occurs when iodine administration in an iodine-deficient individual or someone with pre-existing thyroid abnormalities leads to **hyperthyroidism**. *Drug induced hyperthyroidism* - This is a broad category referring to hyperthyroidism caused by various medications, such as **amiodarone**, but does not specifically define the Wolf-Chaikoff effect. - The Wolf-Chaikoff effect specifically relates to the direct inhibitory action of high **iodine** concentrations on the thyroid gland. *Thyrotoxicosis due to excessive amount of thyroid hormone ingestion* - This condition is known as **thyrotoxicosis factitia** or **exogenous thyrotoxicosis**. - It is distinct from the Wolf-Chaikoff effect, which involves the thyroid gland's self-regulatory response to **iodine** overload rather than external hormone intake.

Question 7: Which hormone is released when serum calcium levels decrease?

A. Parathormone (Correct Answer)
B. Calcitonin
C. Thyroxine
D. Adrenaline

Explanation: ***Parathormone*** - **Parathormone (PTH)** is released from the **parathyroid glands** in response to **low serum calcium levels**. - Its primary function is to **increase serum calcium** by stimulating bone resorption, increasing renal reabsorption of calcium, and enhancing intestinal absorption of calcium (indirectly via vitamin D activation). *Calcitonin* - **Calcitonin** is released from the **thyroid gland** in response to **high serum calcium levels**. - Its main action is to **lower serum calcium** by inhibiting osteoclast activity and increasing renal calcium excretion. *Thyroxine* - **Thyroxine (T4)** is a thyroid hormone primarily involved in **metabolism**, growth, and development. - It does **not directly regulate** serum calcium levels. *Adrenaline* - **Adrenaline (epinephrine)** is a hormone released from the **adrenal glands** in response to stress. - It plays a role in the "fight or flight" response, affecting heart rate, blood pressure, and glucose metabolism, but **not calcium regulation**.

Question 8: All of the following are known functions of hypothalamus except

A. Temperature regulation
B. Hypophyseal control
C. Food intake
D. Increase in heart rate with exercise (Correct Answer)

Explanation: ***Increase in heart rate with exercise*** - The **hypothalamus** has an indirect role in cardiovascular responses during exercise, primarily through its influence on the **autonomic nervous system** to maintain homeostasis. - However, the primary control of increased heart rate during exercise originates from the **medulla oblongata** and the **motor cortex**, which directly modulates the sympathetic nervous system to increase cardiac output. *Temperature regulation* - The **hypothalamus** contains thermoregulatory centers that monitor and adjust body temperature through mechanisms such as **sweating** and **shivering**. - This function is a fundamental aspect of maintaining **homeostasis**. *Hypophyseal control* - The **hypothalamus** directly controls the **pituitary gland** (hypophysis) by producing releasing and inhibiting hormones that regulate the secretion of pituitary hormones. - This neuroendocrine function is crucial for controlling various **endocrine axes**. *Food intake* - The **hypothalamus** plays a key role in regulating appetite and satiety, with specific nuclei like the **arcuate nucleus** integrating signals related to hunger and fullness. - This control is essential for maintaining **energy balance**.

Question 9: At the time point indicated by the arrow, the hormone levels are:

A. Decreased estrogen, increased progesterone
B. Increased estrogen, increased progesterone
C. Decreased estrogen, decreased progesterone
D. Increased estrogen, decreased progesterone (Correct Answer)

Explanation: ***Increased estrogen, decreased progesterone*** - The arrow (red circle) points to Day 14, marking the approximate time of **ovulation**. At this point, the graph shows that **estrogen levels peak** just before ovulation and begin to decrease during ovulation. - Progesterone levels are relatively **low** during the follicular phase and only start to significantly increase **after ovulation** as the corpus luteum forms. *Decreased estrogen, increased progesterone* - This hormonal profile is characteristic of the **mid to late luteal phase**, not ovulation. - During the luteal phase, post-ovulation, the **corpus luteum** predominantly produces **progesterone**, leading to its increase, while estrogen levels decline from their pre-ovulatory peak. *Increased estrogen, increased progesterone* - While estrogen is high just before ovulation, **progesterone remains low** until after ovulation. - An increase in both significant progesterone and estrogen would be more indicative of the middle of the **luteal phase** when the corpus luteum is fully functional and producing both hormones in higher amounts. *Decreased estrogen, decreased progesterone* - This hormone profile typically occurs at the **very end of the luteal phase** if pregnancy does not occur, leading to the breakdown of the corpus luteum and subsequent menstruation. - It also characterizes the early follicular phase, not the time around ovulation.

Question 10: A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?

A. Acetylcholine (Correct Answer)
B. Normetanephrine
C. Metanephrine
D. Epinephrine

Explanation: ***Acetylcholine*** - **Acetylcholine** is the primary neurotransmitter released by **preganglionic sympathetic fibers** that innervate the adrenal medulla. - Upon binding to **nicotinic receptors** on chromaffin cells, acetylcholine stimulates the release of catecholamines, including norepinephrine and epinephrine, into the bloodstream. *Normetanephrine* - **Normetanephrine** is a metabolite of **norepinephrine**, not a hormone that triggers its release. - It is formed by the action of **catechol-O-methyltransferase (COMT)** on norepinephrine. *Metanephrine* - **Metanephrine** is a metabolite of **epinephrine**, not a substance that stimulates catecholamine release from the adrenal medulla. - Like normetanephrine, it is also formed by the action of **COMT**. *Epinephrine* - **Epinephrine** (adrenaline) is a hormone primarily produced and released by the **adrenal medulla**, alongside norepinephrine. - While both are catecholamines, epinephrine does not trigger its own release or the release of norepinephrine in this context; instead, their release is stimulated by acetylcholine.

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