Endocrinology Practice Questions

Q: Intestinal absorption of calcium is mainly increased by?

Calcitriol. ***Calcitriol*** - **Calcitriol** (1,25-dihydroxyvitamin D3) is the hormonally active form of vitamin D, which is essential for increasing **calcium absorption** from the intestines. - It stimulates the synthesis of **calcium-binding proteins** in intestinal epithelial cells, facilitating active transport of calcium. *Parathormone* - **Parathormone (PTH)** primarily regulates calcium by increasing its reabsorption in the **kidneys** and stimulating its release from **bones**. - While it indirectly promotes calcitriol synthesis, its *direct* effect on intestinal calcium absorption is minimal compared to calcitriol. *Glucocorticoids* - **Glucocorticoids** generally have an *inhibitory* effect on calcium absorption in the intestine and can also increase renal excretion of calcium. - Prolonged use can lead to **osteoporosis** due to their negative impact on bone formation and calcium balance. *ACTH* - **ACTH (adrenocorticotropic hormone)** primarily stimulates the adrenal cortex to produce **cortisol** and other glucocorticoids. - It has **no direct role** in regulating calcium absorption from the intestines.

Q: Which of the following cell types is considered insulin-dependent?

Myocytes. ***Myocytes*** - **Myocytes** (skeletal muscle cells) are **insulin-dependent** and represent the **largest site of insulin-mediated glucose disposal** in the body - Insulin promotes translocation of **GLUT4 transporters** to the cell membrane, enabling glucose uptake - Skeletal muscle accounts for approximately **70-80% of postprandial glucose disposal**, making it the most quantitatively significant insulin-dependent tissue *Adipocytes* - **Adipocytes** (fat cells) are also **insulin-dependent** and utilize **GLUT4 transporters** for glucose uptake - Insulin stimulates glucose uptake and conversion to triglycerides for storage - However, adipose tissue accounts for only **10-15% of glucose disposal**, making it less quantitatively significant than skeletal muscle - Both myocytes and adipocytes are considered the two major insulin-dependent tissues in the body *Pituitocytes* - **Pituitocytes** are supporting cells in the pituitary gland - They use **insulin-independent glucose transporters** (GLUT1/GLUT3) - The pituitary gland requires constant glucose supply independent of insulin status *RBCs* - **Red blood cells** lack mitochondria and depend entirely on **anaerobic glycolysis** - Glucose uptake occurs via **insulin-independent GLUT1 transporters** - RBCs must maintain glucose uptake at all times, regardless of insulin levels

Q: Somatomedin-C deficiency causes?

Growth retardation. ***Growth retardation*** - **Somatomedin-C** (also known as **Insulin-like Growth Factor 1 or IGF-1**) is a crucial mediator of **growth hormone's** effects on growth. - A deficiency in Somatomedin-C, therefore, directly leads to **impaired growth** and **stature**, manifesting as **growth retardation**. *Genetic dwarfism* - This term generally refers to dwarfism caused by various **genetic conditions** (e.g., achondroplasia), which may or may not involve the **growth hormone/IGF-1 axis**. - While Somatomedin-C deficiency can be genetic, "genetic dwarfism" is a broader term and not the most precise answer for the direct consequence. *Congenital hypothyroidism* - This condition results from **deficient thyroid hormone production** from birth. - It leads to neurological impairment and **growth failure**, but it is due to **thyroid hormone deficiency**, not Somatomedin-C deficiency. *Type 1 diabetes mellitus* - This is an **autoimmune disease** characterized by the **destruction of pancreatic beta cells**, leading to **insulin deficiency**. - It is entirely unrelated to **Somatomedin-C** or the growth hormone axis.

Q: Which of the following does not stimulate growth hormone (GH) release?

Free fatty acids. ***Free fatty acids*** - High levels of **free fatty acids** in the bloodstream inhibit growth hormone (GH) secretion. - This occurs through a **negative feedback loop** at the level of the hypothalamus and pituitary gland. *Fasting* - **Fasting** (especially prolonged) is a potent stimulus for GH release, helping to mobilize fat stores and maintain **glucose homeostasis**. - During fasting, ghrelin levels increase, which further promotes GH secretion. *Exercise* - **Physical exercise** is a well-known physiological stimulus for GH release, contributing to muscle growth and repair. - The intensity and duration of exercise can influence the magnitude of GH secretion. *Stress* - Various forms of **stress**, including physical (e.g., trauma, surgery) and psychological stress, stimulate GH release. - This response is mediated in part by the **sympathetic nervous system** and increased cortisol levels.

Q: Thyroid hormone binds to which receptor ?

Nuclear. ***Nuclear*** - Thyroid hormones, being **lipid-soluble**, readily diffuse across the **cell membrane** to bind to receptors located in the nucleus. - This binding directly influences **gene expression** and protein synthesis, mediating the hormone's effects. *Membrane* - Membrane receptors typically bind **water-soluble hormones** (e.g., peptide hormones, catecholamines) that cannot freely cross the cell membrane. - These interactions usually trigger a **second messenger cascade** within the cell. *Cytoplasmic* - While some **steroid hormones** bind to cytoplasmic receptors which then translocate to the nucleus, thyroid hormones bind directly to nuclear receptors. - Cytoplasmic receptors are located in the **cytosol** before their ligand-induced translocation. *None of the options* - This option is incorrect, as thyroid hormones have a specific and well-defined receptor location. - The direct action on **gene regulation** necessitates a nuclear receptor.

Q: What is the half-life of the thyroid hormone triiodothyronine (T3)?

1 day. ***1 day*** - The **half-life of T3 (triiodothyronine)** is approximately **1 day (24 hours)**, making its biological effects relatively rapid compared to T4. - This shorter half-life contributes to its quicker onset and offset of action. *8 hours* - While reflecting a relatively short duration, **8 hours** is not the accepted half-life for T3. - This value is too short for T3, which has a more sustained biological effect. *6 hours* - A half-life of **6 hours** is too short for T3, which has a more sustained effect than such a rapid clearance would suggest. - This would imply a much faster metabolic turnover than observed clinically. *10 days* - **10 days** is longer than the actual **half-life of T4 (thyroxine)**, which is approximately **7 days**. - T4 serves as a prohormone and is more extensively protein-bound, contributing to its prolonged presence in circulation compared to T3.

Q: Which of the following hormones does not increase in response to stress?

thyroxine. ***Correct: Thyroxine*** - **Thyroxine (T4)** does not acutely increase in response to stress - Thyroid hormones are **not part of the immediate stress response** mediated by the HPA axis - During acute stress, **TSH may actually be suppressed** by elevated cortisol - Chronic stress can affect thyroid function, but there is **no immediate surge** in T4 levels like with other stress hormones *Incorrect: ADH* - **Antidiuretic hormone (ADH/vasopressin)** is a key stress hormone - Released rapidly in response to **physical stress, pain, hypovolemia**, and hypotension - Part of the **neurohypophyseal stress response** to maintain blood pressure and volume - Works alongside cortisol in the stress response *Incorrect: GH* - **Growth hormone** levels increase during **acute stress** (physical and psychological) - Stimulated by stress-induced activation of **GHRH** and suppression of somatostatin - Promotes **gluconeogenesis and lipolysis** during metabolic stress - Part of the counter-regulatory hormone response *Incorrect: None of the options* - This option is incorrect because **thyroxine is the correct answer** - Thyroxine does not acutely increase with stress, unlike ADH and GH

Q: Which of the following actions of growth hormone (GH) is primarily mediated by insulin-like growth factor 1 (IGF-1)?

Linear growth and bone development. ***Linear growth and bone development*** - **IGF-1 (Somatomedin C)** is the primary mediator of growth hormone's effects on **linear growth and skeletal development** - IGF-1 is produced primarily in the liver in response to GH stimulation - Acts on **epiphyseal growth plates** to promote chondrocyte proliferation and differentiation - Mediates **protein synthesis, muscle growth, and bone mineralization** - This represents the classic **somatomedin hypothesis** - GH stimulates IGF-1 production, which then mediates growth effects *Lipolysis* - Growth hormone **directly** promotes lipolysis through GH receptors on adipocytes - This leads to breakdown of triglycerides into free fatty acids and glycerol - This is a **direct metabolic effect** of GH, independent of IGF-1 *Insulin resistance* - GH **directly** induces insulin resistance through its own receptors - This is one of the **diabetogenic effects** of GH - While IGF-1 can influence insulin sensitivity, insulin resistance is primarily a **direct GH effect** *Sodium retention* - GH has **direct effects** on renal tubules to promote sodium and water retention - This antinatriuretic effect occurs through GH receptors in the kidney - Not primarily mediated by IGF-1

Q: Which hormone increases with age?

Parathormone. ***Parathormone*** - **Parathormone (PTH)** levels in the blood tend to increase with age, often due to a decline in renal function and reduced vitamin D synthesis, leading to compensatory hyperparathyroidism. - This age-related increase in PTH can contribute to **bone demineralization** and an increased risk of osteoporosis. *GH* - **Growth hormone (GH)** levels generally **decrease with age**, leading to a condition known as somatopause. - Reduced GH contributes to changes in body composition, such as increased adiposity and decreased lean muscle mass, as well as reduced bone density. *Prolactin* - **Prolactin** levels typically remain relatively stable or may slightly decrease with age in men, while in women they can fluctuate due to hormonal changes like menopause but do not show a consistent increase with age. - High prolactin levels are often associated with specific pathological conditions like **prolactinomas** rather than normal aging. *Insulin* - While **insulin resistance** often increases with age, leading to higher fasting insulin levels in some individuals, the overall picture of insulin secretion can be complex and is often influenced by factors such as diet, exercise, and genetics rather than solely age. - A *decline in pancreatic beta-cell function* with age can also lead to impaired insulin secretion in some elderly individuals, complicating the simple relationship between age and insulin levels.

Question 1

Intestinal absorption of calcium is mainly increased by?

Accepted Answer

Calcitriol

Answer

Parathormone

Answer

Glucocorticoids

Answer

ACTH

Question 2

Which of the following cell types is considered insulin-dependent?

Accepted Answer

Myocytes

Answer

Pituitocytes

Answer

Adipocytes

Answer

RBCs

Question 3

Somatomedin-C deficiency causes?

Accepted Answer

Growth retardation

Answer

Genetic dwarfism

Answer

Congenital hypothyroidism

Answer

Type 1 diabetes mellitus

Question 4

Which of the following does not stimulate growth hormone (GH) release?

Accepted Answer

Free fatty acids

Answer

Exercise

Answer

Fasting

Answer

Stress

Question 5

Thyroid hormone binds to which receptor ?

Accepted Answer

Nuclear

Answer

Membrane

Answer

Cytoplasmic

Answer

None of the options

Question 6

What is the half-life of the thyroid hormone triiodothyronine (T3)?

Accepted Answer

1 day

Answer

8 hours

Answer

6 hours

Answer

10 days

Question 7

Which of the following statements about thyroid hormone receptors is correct?

Accepted Answer

They are intracellular receptors that mediate gene transcription after binding with T3 or T4, but their primary action is through T3.

Answer

They directly bind to thyrotropin-releasing hormone (TRH)

Answer

They directly bind to thyroid-stimulating hormone (TSH)

Answer

They cause nuclear transcription after binding with T4

Question 8

Which of the following hormones does not increase in response to stress?

Accepted Answer

thyroxine

Answer

None of the options

Answer

ADH

Answer

GH

Question 9

Which of the following actions of growth hormone (GH) is primarily mediated by insulin-like growth factor 1 (IGF-1)?

Accepted Answer

Linear growth and bone development

Answer

Lipolysis

Answer

Sodium retention

Answer

Insulin resistance

Question 10

Which hormone increases with age?

Accepted Answer

Parathormone

Answer

GH

Answer

Prolactin

Answer

Insulin

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?