Endocrinology Practice Questions

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 is not an effect of insulin?

Increased glycogenolysis. ***Increased glycogenolysis*** - Insulin primarily **inhibits glycogenolysis** (the breakdown of glycogen) and promotes glycogen synthesis to lower blood glucose levels. - Thus, increased glycogenolysis is the opposite of an insulin effect. *Increased transport of glucose into cells* - Insulin **facilitates the uptake of glucose** into insulin-sensitive cells (muscle and adipose tissue) by promoting the translocation of GLUT4 transporters to the cell membrane. - This action helps to remove glucose from the bloodstream and reduce blood sugar. *Induction of lipoprotein lipase* - Insulin **activates lipoprotein lipase (LPL)**, an enzyme that breaks down triglycerides in chylomicrons and VLDL into free fatty acids for storage in adipose tissue. - This promotes energy storage after a meal. *Decreased gluconeogenesis* - Insulin **suppresses hepatic gluconeogenesis**, the process by which the liver synthesizes glucose from non-carbohydrate precursors. - This helps to reduce the liver's glucose output and lower blood glucose levels.

Q: Acidophilic cells of anterior pituitary secrete?

GH. ***GH*** - **Growth Hormone (GH)** is secreted by **somatotrophs**, which are a type of acidophilic cell in the anterior pituitary. - These cells stain readily with **acidic dyes** due to their abundant secretory granules. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is secreted by **corticotrophs**, which are **basophilic cells** in the anterior pituitary. - Corticotrophs stain with basic dyes due to different intracellular granule content. *TSH* - **Thyroid-stimulating hormone (TSH)** is secreted by **thyrotrophs**, which are a type of **basophilic cell** in the anterior pituitary. - Basophilic cells are characterized by their affinity for basic dyes. *ADH* - **Antidiuretic hormone (ADH)**, also known as vasopressin, is produced by the **hypothalamus** and released from the **posterior pituitary**, not the anterior pituitary. - It is not secreted by acidophilic cells.

Q: Which hormone is converted into its active form in the liver?

Thyroid hormone. ***Thyroid hormone*** - The liver is a major site for the conversion of **thyroxine (T4)**, the primary hormone secreted by the thyroid gland, into its more active form, **triiodothyronine (T3)**. - This conversion, primarily through **deiodination**, is critical for thyroid hormone action in target tissues throughout the body. *Corticosteroid* - **Cortisol**, the main human corticosteroid, is directly secreted by the **adrenal cortex** in its active form. - While the liver metabolizes cortisol for excretion, it does not convert an inactive form into an active corticosteroid. *Estradiol* - **Estradiol** is primarily produced and secreted in its active form by the **ovaries** in premenopausal women. - The liver is involved in the metabolism and conjugation of estradiol for excretion, not its activation. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is secreted by the **anterior pituitary gland** in its active form. - Its primary role is to stimulate the adrenal cortex to produce cortisol; it does not undergo activation in the liver.

Q: Insulin acts by which pathway-

Tyrosine kinase. ***Tyrosine kinase*** - Insulin binds to its receptor, a **receptor tyrosine kinase**, activating the intracellular tyrosine kinase domain. - This activation leads to the **autophosphorylation** of the receptor and subsequent phosphorylation of various intracellular substrates, initiating a signaling cascade. *Intrinsic ion channel* - This mechanism involves a receptor that is itself an **ion channel**, opening or closing to allow ions to pass through the cell membrane upon ligand binding. - Insulin's primary action is not to alter membrane permeability via direct ion channel modulation but rather to initiate an intracellular signaling cascade. *JAK-STAT-Kinase* - The **JAK-STAT pathway** is typically utilized by cytokine receptors (e.g., growth hormone, interleukins) that do not possess intrinsic kinase activity but activate associated soluble kinases like JAK. - Insulin signaling primarily utilizes its intrinsic tyrosine kinase activity rather than recruiting JAK kinases. *Transcription factor* - While insulin ultimately influences gene expression and thus the activity of **transcription factors**, it is not a transcription factor itself. - Insulin's initial binding and signaling occur at the cell surface via its receptor, leading to downstream events that *regulate* transcription factor activity.

Question 1

Which of the following is a calorigenic hormone?

Accepted Answer

All of the options

Answer

Norepinephrine

Answer

Epinephrine

Answer

Thyroid hormones

Question 2

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

Accepted Answer

Growth hormone

Answer

PTH

Answer

ACTH

Answer

Insulin

Question 3

Major androgen precursor from adrenal cortex is

Accepted Answer

DHEA

Answer

Testosterone

Answer

Dihydrotestosterone

Answer

Androstenedione

Question 4

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 5

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 6

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 7

Which of the following is not an effect of insulin?

Accepted Answer

Increased glycogenolysis

Answer

Increased transport of glucose into cells

Answer

Induction of lipoprotein lipase

Answer

Decreased gluconeogenesis

Question 8

Acidophilic cells of anterior pituitary secrete?

Accepted Answer

GH

Answer

ACTH

Answer

TSH

Answer

ADH

Question 9

Which hormone is converted into its active form in the liver?

Accepted Answer

Thyroid hormone

Answer

Corticosteroid

Answer

Estradiol

Answer

ACTH

Question 10

Insulin acts by which pathway-

Accepted Answer

Tyrosine kinase

Answer

Intrinsic ion channel

Answer

JAK-STAT-Kinase

Answer

Transcription factor

Endocrinology — MCQs

Endocrinology — MCQs

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