Endocrinology Practice Questions

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

Estradiol. ***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.

Q: Estradiol is a powerful inhibitor of FSH (follicle stimulating hormone). What is another factor that is a powerful inhibitor of FSH in the female?

Inhibin. ***Inhibin*** - **Inhibin** is a glycoprotein hormone primarily produced by the **granulosa cells** of the ovarian follicles. - It selectively inhibits the secretion of **FSH** from the anterior pituitary, providing negative feedback without significantly affecting LH. *LH* - **Luteinizing hormone (LH)** is primarily involved in stimulating ovulation and the production of progesterone, not directly inhibiting FSH. - While LH and FSH levels are intricately linked in the menstrual cycle, LH does not act as a primary inhibitor of FSH. *Testosterone* - **Testosterone** is an androgen primarily found at much lower levels in females compared to males and does not serve as a primary inhibitor of FSH in the female reproductive axis. - While androgens can influence follicular development, they are not a direct and potent inhibitor of FSH secretion. *Progesterone* - **Progesterone** is mainly involved in preparing the uterus for pregnancy and maintaining it, and it provides negative feedback on both LH and FSH, but its primary effect is often associated with LH suppression and the overall luteal phase regulation rather than specific, potent FSH inhibition like inhibin. - High levels of progesterone during the luteal phase do inhibit GnRH, which in turn reduces FSH and LH, but inhibin specifically targets FSH.

Q: In hypoparathyroidism:

Plasma calcium is low and inorganic phosphorous high. ***Plasma calcium is low and inorganic phosphorous high*** - **Hypoparathyroidism** is characterized by insufficient parathyroid hormone (PTH) production, leading to decreased bone resorption and reduced renal reabsorption of calcium [1]. This results in **hypocalcemia** (low plasma calcium) [1]. - PTH also promotes renal excretion of phosphate [2]. With insufficient PTH, renal phosphate excretion is impaired, leading to **hyperphosphatemia** (high inorganic phosphorus) [1]. *Plasma calcium is high and inorganic phosphorous low* - This profile is characteristic of **primary hyperparathyroidism**, where excessive PTH causes increased bone resorption and renal calcium reabsorption (high calcium), and increased renal phosphate excretion (low phosphorus). - It directly contradicts the defining features of hypoparathyroidism [1]. *Plasma calcium and inorganic phosphorous are low* - While plasma calcium is low in hypoparathyroidism, plasma inorganic phosphorus is characteristically high, not low [1]. - A combination of low calcium and low phosphorus can be seen in conditions like **vitamin D deficiency** (osteomalacia), but not directly in pure hypoparathyroidism [1]. *Plasma calcium and inorganic phosphorous are high* - This combination of high calcium and high phosphorus is uncommon and not typically seen in either hypoparathyroidism or hyperparathyroidism. - It could potentially indicate conditions like **milk-alkali syndrome** or **vitamin D intoxication**, but not hypoparathyroidism, which is defined by low calcium [1].

Q: Which of the following is a calorigenic hormone?

All of the options. ***All of the options*** - **Norepinephrine**, **epinephrine**, and **thyroid hormones** all increase the **basal metabolic rate** and **heat production**, classifying them as calorigenic. - These hormones stimulate cellular metabolism, leading to increased **oxygen consumption** and **ATP hydrolysis**, which generates heat. *Norepinephrine* - **Norepinephrine** promotes increased **thermogenesis** through its effects on various tissues, particularly brown adipose tissue. - It enhances the breakdown of **fat stores** and **glucose** to generate heat, contributing to the body's overall energy expenditure. *Epinephrine* - **Epinephrine** rapidly increases the **metabolic rate** and heat production during stress or exercise through its beta-adrenergic effects. - It stimulates **glycogenolysis** and **lipolysis**, providing substrates for energy production and subsequent heat generation. *Thyroid hormones* - **Thyroid hormones** (T3 and T4) are major regulators of the **basal metabolic rate** in nearly all body tissues. - They increase the activity of the **Na+/K+ ATPase pump** and mitochondrial oxidative phosphorylation, both of which are significant sources of heat.

Q: TRH stimulation testing is useful in diagnosis of disorders of the following hormones?

Growth hormone. ***Growth hormone*** - **TRH** (Thyrotropin-Releasing Hormone) normally stimulates the release of **TSH** and **prolactin** from the anterior pituitary, but **does not normally affect growth hormone**. - In certain pathological conditions like **acromegaly**, TRH can **paradoxically stimulate growth hormone release**, where GH levels abnormally increase instead of remaining unchanged. - This **paradoxical GH response to TRH** is used as a diagnostic test in suspected acromegaly patients, helping differentiate it from normal physiology. - Note: The primary uses of TRH stimulation are for assessing **TSH** (thyroid axis disorders) and **prolactin** (hyperprolactinemia), but among the given options, growth hormone is the relevant answer. *PTH* - **PTH** (Parathyroid Hormone) regulation is primarily controlled by **serum calcium levels**, not by TRH. - Disorders of PTH are diagnosed through **calcium, phosphate, and PTH measurements**, not TRH stimulation. *ACTH* - **ACTH** (Adrenocorticotropic Hormone) release is stimulated by **CRH** (Corticotropin-Releasing Hormone), not TRH. - Conditions involving ACTH are typically evaluated using **CRH stimulation tests** or **dexamethasone suppression tests**. *Insulin* - **Insulin** secretion by pancreatic beta cells is primarily regulated by **blood glucose levels**, not by TRH. - Insulin-related disorders are diagnosed through **glucose tolerance tests**, **C-peptide levels**, and **insulin measurements**.

Q: Major androgen precursor from adrenal cortex is

DHEA. ***DHEA*** - **Dehydroepiandrosterone (DHEA)** is the most abundant and potent **androgen precursor** produced by the adrenal cortex. - It is then converted in peripheral tissues to more potent androgens like testosterone and dihydrotestosterone. *Testosterone* - While testosterone is a potent androgen, its primary source is the **gonads** (testes in males, ovaries in females), not the adrenal cortex. - The adrenal cortex produces only small amounts of testosterone directly. *Dihydrotestosterone* - **Dihydrotestosterone (DHT)** is the most potent androgen, but it is primarily formed in target tissues from **testosterone** via the enzyme **5-alpha-reductase**. - The adrenal cortex does not directly produce significant amounts of DHT. *Androstenedione* - **Androstenedione** is also an adrenal androgen precursor, but it is produced in smaller quantities and is less potent than DHEA. - While it can be converted to testosterone, **DHEA** is considered the major overall androgen precursor from the adrenal gland due to its abundance.

Q: Which is true about Sex hormone-binding globulin (SHBG):

Binds testosterone with a higher affinity than estradiol. ***Binds testosterone with a higher affinity than estradiol*** - SHBG has a **higher binding affinity for androgens** (**testosterone** and dihydrotestosterone) than for estrogens like **estradiol**. - This difference in affinity is crucial for regulating the **bioavailability of sex hormones**. *Stimulates the secretion of inhibin* - **Inhibin** secretion is primarily stimulated by **follicle-stimulating hormone (FSH)** and local factors in the gonads, not by SHBG. - SHBG's main role is to transport sex steroids, not to directly stimulate other hormone productions. *Reduces the total amount of circulating testosterone* - SHBG **binds circulating testosterone**, but it does not *reduce* the total amount; rather, it *regulates the free fraction* of testosterone. - The liver produces SHBG, which then acts as a **carrier protein**, affecting the bioavailability of **sex hormones**. *Decreases the half-life of testosterone* - By binding to testosterone, SHBG **increases the half-life** of testosterone by protecting it from rapid metabolic degradation and excretion. - **Bound hormones** are less readily metabolized and excreted, thus prolonging their circulation time.

Q: GH secretion is increased during:

Increases on prolonged fasting. ***Increases on prolonged fasting*** - Growth Hormone (GH) secretion **significantly increases during prolonged fasting** as a crucial **counter-regulatory mechanism**. - GH promotes **lipolysis** (fat breakdown) and **gluconeogenesis**, helping maintain blood glucose while preserving protein stores. - During fasting, GH levels can increase **5-fold or more**, working alongside cortisol and glucagon to maintain metabolic homeostasis. - This is a well-established physiological response critical for survival during food deprivation. *Greater in the early morning* - GH secretion follows a **circadian rhythm** with peak secretion during **deep slow-wave sleep (stage 3-4 NREM)**. - This peak typically occurs in the **first half of the night** (e.g., 11 PM - 2 AM), not specifically in the "early morning" hours (5-7 AM). - By early morning, GH levels are typically declining as sleep becomes lighter. *Greater in the evening* - GH secretion is **lowest during waking hours**, including the evening. - The major pulsatile release begins **after sleep onset**, not during evening wakefulness. *Stimulates B-cells of pancreas directly* - GH does **not directly stimulate pancreatic β-cells**. - GH has **diabetogenic effects** by promoting hepatic glucose output and inducing **insulin resistance** in peripheral tissues. - Any increase in insulin secretion is **indirect**, resulting from elevated blood glucose, not direct β-cell stimulation.

Q: Parathormone has all of the following effects, except -

Increased phosphate reabsorption in kidney. ***Increased phosphate reabsorption in kidney*** - Parathormone (**PTH**) primarily functions to increase serum **calcium** levels. - One of its key actions is to promote **phosphate excretion** by decreasing phosphate reabsorption in the renal tubules, not increasing it. *Increased calcitriol synthesis* - **PTH** stimulates the renal 1-alpha-hydroxylase enzyme, which is crucial for converting 25-hydroxyvitamin D to its active form, **1,25-dihydroxyvitamin D (calcitriol)**. - This active form of **vitamin D** then enhances intestinal calcium absorption. *Increased Ca+2 reabsorption in kidney* - **PTH** directly acts on the renal tubules, particularly the distal tubule and collecting duct, to increase the **reabsorption of calcium**. - This prevents calcium loss from the body and contributes to raising serum calcium levels. *Increased bone resorption* - **PTH** stimulates osteoclasts, leading to the breakdown of bone and the release of **calcium** and phosphate into the bloodstream. - This process, known as **bone resorption**, is a significant mechanism by which PTH increases serum calcium.

Q: Which of the following areas of the adrenal gland would you expect to increase in activity in a patient subjected to salt restriction?

Zona glomerulosa of the adrenal cortex. ***Zona glomerulosa of the adrenal cortex*** - Salt restriction leads to a decrease in **extracellular fluid volume** and an increase in **potassium** levels, which are potent stimulators for **aldosterone** release. - The **zona glomerulosa** is responsible for synthesizing and secreting aldosterone, a **mineralocorticoid** that helps regulate sodium and potassium balance. *Zona fasciculata of the adrenal cortex* - This layer primarily secretes **glucocorticoids (e.g., cortisol)**, which are involved in stress response and metabolism. - Their activity increases in response to **ACTH**, not directly due to salt restriction. *Zona reticularis of the adrenal cortex* - This layer produces **adrenal androgens** (e.g., DHEA), which are precursors to sex hormones. - Its activity is stimulated by **ACTH**, and it does not play a significant role in salt and water balance. *Adrenal medulla* - The adrenal medulla secretes **catecholamines (epinephrine and norepinephrine)**, which are involved in the "fight or flight" response. - These hormones are released in response to sympathetic nervous system activation and are not directly involved in regulating salt balance.

Question 1

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

Accepted Answer

Estradiol

Answer

Epinephrine

Answer

Glucagon

Answer

Thyrotropin

Question 2

Estradiol is a powerful inhibitor of FSH (follicle stimulating hormone). What is another factor that is a powerful inhibitor of FSH in the female?

Accepted Answer

Inhibin

Answer

LH

Answer

Testosterone

Answer

Progesterone

Question 3

In hypoparathyroidism:

Accepted Answer

Plasma calcium is low and inorganic phosphorous high

Answer

Plasma calcium is high and inorganic phosphorous low

Answer

Plasma calcium and inorganic phosphorous are low

Answer

Plasma calcium and inorganic phosphorous are high

Question 4

Which of the following is a calorigenic hormone?

Accepted Answer

All of the options

Answer

Norepinephrine

Answer

Epinephrine

Answer

Thyroid hormones

Question 5

TRH stimulation testing is useful in diagnosis of disorders of the following hormones?

Accepted Answer

Growth hormone

Answer

PTH

Answer

ACTH

Answer

Insulin

Question 6

Major androgen precursor from adrenal cortex is

Accepted Answer

DHEA

Answer

Testosterone

Answer

Dihydrotestosterone

Answer

Androstenedione

Question 7

Which is true about Sex hormone-binding globulin (SHBG):

Accepted Answer

Binds testosterone with a higher affinity than estradiol

Answer

Stimulates the secretion of inhibin

Answer

Reduces the total amount of circulating testosterone

Answer

Decreases the half-life of testosterone

Question 8

GH secretion is increased during:

Accepted Answer

Increases on prolonged fasting

Answer

Greater in the early morning

Answer

Greater in the evening

Answer

Stimulates B-cells of pancreas directly

Question 9

Parathormone has all of the following effects, except -

Accepted Answer

Increased phosphate reabsorption in kidney

Answer

Increased calcitriol synthesis

Answer

Increased Ca+2 reabsorption in kidney

Answer

Increased bone resorption

Question 10

Which of the following areas of the adrenal gland would you expect to increase in activity in a patient subjected to salt restriction?

Accepted Answer

Zona glomerulosa of the adrenal cortex

Answer

Zona fasciculata of the adrenal cortex

Answer

Zona reticularis of the adrenal cortex

Answer

Adrenal medulla

Endocrinology — MCQs

Endocrinology — MCQs

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