Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 781: At what weeks of gestation is the fetal thyroid gland capable of synthesizing hormones?

A. 6-7 weeks
B. 7-8 weeks
C. 10-12 weeks (Correct Answer)
D. 12-14 weeks

Explanation: ***10-12 weeks*** - The fetal thyroid gland begins to develop around **3-4 weeks of gestation** but becomes functionally mature enough to **synthesize hormones (thyroxine and triiodothyronine)** by 10-12 weeks. - At this stage, the fetal pituitary gland starts secreting **thyroid-stimulating hormone (TSH)**, which stimulates the fetal thyroid to produce and secrete its own hormones. *6-7 weeks* - While the **thyroid primordium** is forming and descending during this period, it is not yet capable of synthesizing significant amounts of hormones. - This stage is primarily characterized by the **morphological development** of the gland. *7-8 weeks* - The fetal thyroid gland continues to differentiate and grow during these weeks, but the **follicles are not yet fully developed or active** in hormone synthesis. - **Iodide trapping** begins around this time, which is a precursor to hormone synthesis. *12-14 weeks* - By this stage, the fetal thyroid is **actively synthesizing and secreting hormones**, and fetal thyroid function is well established. - However, the initial capability for synthesis begins slightly earlier, around **10-12 weeks**.

Question 782: Human placental lactogen (HPL) has activity similar to which hormone?

A. Growth hormone (Correct Answer)
B. Oxytocin
C. Insulin
D. All of the options

Explanation: **Growth hormone** - **Human placental lactogen (HPL)**, also known as **human chorionic somatomammotropin (hCS)**, is a polypeptide hormone produced by the placental syncytiotrophoblast. - HPL shares approximately **96% structural homology** with **growth hormone (GH)** and has both **somatotropic** (growth-promoting) and **lactogenic** activities. - HPL acts on maternal metabolism by promoting **lipolysis**, **insulin resistance**, and maintaining **glucose availability** for the fetus—actions similar to growth hormone's metabolic effects. - This makes growth hormone the correct answer for hormones with similar activity to HPL. *Oxytocin* - **Oxytocin** is a posterior pituitary hormone primarily involved in **uterine contractions** during labor and **milk ejection reflex** during lactation. - It is structurally a nonapeptide and functionally unrelated to HPL's metabolic and growth-promoting effects. - HPL has no structural or functional similarity to oxytocin. *Insulin* - **Insulin** is a pancreatic hormone that promotes **glucose uptake** by cells and **lowers blood glucose** levels. - While HPL causes maternal **insulin resistance** (anti-insulin effect) to spare glucose for the fetus, HPL itself does not have insulin-like activity. - HPL and insulin are structurally and functionally distinct hormones with opposing metabolic effects. *All of the options* - HPL has specific activity similar to **growth hormone** due to structural homology and shared metabolic actions. - HPL does **not** have activity similar to oxytocin or insulin. - Therefore, this option is incorrect as HPL's activity does not mimic all listed hormones.

Question 783: For how many weeks do cortisol levels typically remain elevated following a hemorrhage?

A. 1 week
B. 2 weeks (Correct Answer)
C. 3 weeks
D. 4 weeks

Explanation: ***2 weeks*** - Following a hemorrhage, the **stress response** leads to elevated cortisol levels which typically persist for approximately **2 weeks**. - This sustained elevation is part of the body's adaptive response to trauma, influencing metabolism and immune function. *1 week* - While cortisol levels rise acutely after hemorrhage, they generally remain elevated for a longer period than just **1 week**. - A 1-week duration would be too short for the typical sustained systemic stress response. *3 weeks* - Cortisol levels usually begin to normalize or return closer to baseline around the **2-week** mark, making 3 weeks an overestimation of the typical sustained elevation. - Prolonged elevation beyond 2 weeks might suggest persistent stress or comorbidity, rather than a normal recovery trajectory. *4 weeks* - A 4-week elevation of cortisol following a single hemorrhage is generally considered an unusually prolonged response and is not typical. - Such an extended elevation could indicate a more severe or complicated clinical course, or a different underlying pathology.

Question 784: Which of the following statements best describes the primary action of ACTH on cortisol secretion?

A. Cortisol secretion follows a diurnal rhythm, peaking in the morning.
B. ACTH stimulates cortisol secretion from the adrenal glands. (Correct Answer)
C. ACTH primarily regulates glucocorticoid secretion, not mineralocorticoid secretion.
D. ACTH is derived from proopiomelanocortin (POMC), but this is unrelated to cortisol secretion.

Explanation: ***ACTH stimulates cortisol secretion from the adrenal glands.*** - **Adrenocorticotropic hormone (ACTH)** is the primary physiological stimulus for the synthesis and secretion of **cortisol** from the zona fasciculata of the adrenal cortex. - ACTH binds to receptors on adrenal cortical cells, activating a signaling cascade that upregulates the enzymes involved in **cholesterol conversion to cortisol**. *Cortisol secretion follows a diurnal rhythm, peaking in the morning.* - While **cortisol secretion** indeed follows a **diurnal rhythm** and peaks in the morning, this statement describes a characteristic of cortisol release itself, not the **primary action of ACTH** *on* cortisol secretion. - The diurnal rhythm *is* largely driven by rhythmic ACTH release, but the question asks for the primary action of ACTH. *ACTH primarily regulates glucocorticoid secretion, not mineralocorticoid secretion.* - ACTH is indeed the most important regulator of **glucocorticoid (cortisol) secretion**, but it also has a minor, transient effect on **mineralocorticoid (aldosterone) secretion**. - **Aldosterone secretion** is primarily regulated by the **renin-angiotensin-aldosterone system** and plasma potassium levels, not ACTH. *ACTH is derived from proopiomelanocortin (POMC), but this is unrelated to cortisol secretion.* - While it is true that **ACTH is derived from proopiomelanocortin (POMC)**, the second part of the statement, asserting that this process is **unrelated to cortisol secretion**, is incorrect. - The formation of ACTH from POMC is directly linked to its role in stimulating cortisol production.

Question 785: Which hormone primarily regulates glucose levels and has indirect effects on ion concentrations in cells?

A. GH
B. Thyroxine
C. Insulin (Correct Answer)
D. Estrogen

Explanation: ***Insulin*** - **Insulin** is the primary hormone responsible for regulating **blood glucose levels** by promoting glucose uptake into cells and stimulating **glycogenesis**. - Beyond glucose, insulin also promotes the uptake of **potassium** into cells, thus impacting ion concentrations. *GH* - **Growth hormone (GH)** primarily promotes **growth** and **protein synthesis** and has an **anti-insulin effect**, increasing blood glucose rather than lowering it. - While GH can influence electrolyte balance indirectly through growth and metabolic processes, it is not its primary regulatory function. *Thyroxine* - **Thyroxine (T4)** is a **thyroid hormone** that primarily regulates **metabolic rate**, influencing energy expenditure, heart rate, and body temperature. - While it affects overall cellular metabolism, it does not directly regulate glucose or ion concentrations in the same immediate way as insulin. *Estrogen* - **Estrogen** is a **sex hormone** primarily involved in the development and regulation of the **female reproductive system** and secondary sexual characteristics. - Although it can have broad metabolic effects, including some influence on glucose metabolism, it is not a primary regulator of blood glucose or ion concentrations.

Question 786: What is the primary function of Ghrelin in the human body?

A. Stimulate water absorption
B. Regulation of temperature
C. Stimulate lipogenesis
D. Increase appetite (Correct Answer)

Explanation: ***Increase appetite*** - **Ghrelin** is often referred to as the "**hunger hormone**" because its primary function is to stimulate appetite. - It is secreted predominantly by the **stomach** when it's empty, signaling the brain that it's time to eat. *Stimulate water absorption* - **Water absorption** primarily occurs in the intestines and is regulated by hormones like **antidiuretic hormone (ADH)**, not ghrelin. - Ghrelin's physiological role is related to energy balance and hunger, not fluid homeostasis. *Regulation of temperature* - **Thermoregulation** is primarily controlled by the **hypothalamus** in the brain, with various hormones and physiological mechanisms involved. - Ghrelin is not directly involved in maintaining body temperature. *Stimulate lipogenesis* - While ghrelin does play a role in **energy storage** by influencing metabolism, its direct and primary action is not to stimulate lipogenesis (fat synthesis). - Its main role is to **induce hunger**, which indirectly leads to increased caloric intake and potential fat storage.

Question 787: Growth hormone has its effect on growth through?

A. Directly
B. Thyroxine
C. Intranuclear receptors
D. IGF-1 (Correct Answer)

Explanation: ***IGF-1*** - **Growth hormone (GH)** primarily exerts its growth-promoting effects indirectly by stimulating the liver and other tissues to produce **insulin-like growth factor 1 (IGF-1)**. - IGF-1 then acts on target tissues to promote **cell proliferation** and **growth**. *Directly* - While GH does have some direct metabolic effects, its significant impact on **growth and development** is mediated through IGF-1, not direct action. - For instance, GH directly promotes **lipolysis** and **anti-insulin effects** but doesn't directly stimulate skeletal growth in a major way. *Thyroxine* - **Thyroxine (thyroid hormone)** is crucial for normal growth and development, especially of the **nervous system**, but it is a distinct hormone from GH. - Although thyroid hormones are permissive for GH action, they do not mediate the primary growth-promoting effects of GH. *Intranuclear receptors* - **Intranuclear receptors** are typically associated with steroid hormones and thyroid hormones, which bind to receptors inside the cell to influence gene expression. - Growth hormone, being a **peptide hormone**, primarily acts on **cell surface receptors** (tyrosine kinase-associated receptors) rather than intranuclear receptors.

Question 788: Insulin secretion is normally stimulated by ?

A. Glucagon-like peptide-1 (GLP-1) (Correct Answer)
B. Vasoactive intestinal peptide (VIP)
C. Alpha-adrenergic receptors
D. Peptide YY (PYY)

Explanation: ***Glucagon-like peptide-1 (GLP-1)*** - **GLP-1** is an **incretin hormone** secreted by intestinal L cells in response to food intake, which **potentiates glucose-dependent insulin secretion** from pancreatic beta cells. - It also plays a role in slowing gastric emptying, promoting satiety, and inhibiting glucagon release, all contributing to better glucose control. *Vasoactive intestinal peptide (VIP)* - **VIP** is a neuropeptide that primarily acts as a **vasodilator** and a neurotransmitter in the gastrointestinal tract, influencing smooth muscle relaxation and water/electrolyte secretion. - While it can impact pancreatic function, its primary role is not the direct stimulation of insulin secretion. *Alpha-adrenergic receptors* - Activation of **alpha-2 adrenergic receptors** on pancreatic beta cells by catecholamines like epinephrine and norepinephrine actually **inhibits insulin secretion**. - This response is part of the "fight or flight" mechanism, conserving glucose for immediate energy demands. *Peptide YY (PYY)* - **PYY** is a hormone released from the gut in response to food that primarily **reduces appetite** and **gastric motility**. - It is known for its role in hunger regulation and energy balance, not as a direct stimulator of insulin release.

Question 789: Which hormone stimulates the thyroid gland during pregnancy?

A. Human placental lactogen
B. ACTH
C. HCG (Correct Answer)
D. Prolactin

Explanation: **HCG** - **Human Chorionic Gonadotropin (HCG)**, produced by the placenta, has structural similarities to **TSH** and can bind to TSH receptors, directly stimulating the thyroid gland. - This stimulation contributes to the physiological changes in thyroid function observed during pregnancy, often leading to a slight increase in **thyroid hormone production**. *Prolactin* - **Prolactin** is primarily involved in **milk production** (lactation) and has no direct stimulatory effect on the thyroid gland. - While prolactin levels rise during pregnancy and postpartum, its role is unrelated to thyroid hormone synthesis. *Human placental lactogen* - **Human placental lactogen (HPL)**, also known as chorionic somatomammotropin, plays a role in **maternal metabolism** and **fetal growth**. - It has anti-insulin effects and promotes lipolysis but does not directly stimulate the thyroid gland. *ACTH* - **Adrenocorticotropic hormone (ACTH)** primarily stimulates the **adrenal cortex** to produce corticosteroids. - It is a key regulator of the **hypothalamic-pituitary-adrenal axis** and has no direct influence on thyroid gland function.

Question 790: Which of the following conditions is not directly caused by growth hormone?

A. Diabetes mellitus
B. Hypothyroidism (Correct Answer)
C. Gigantism
D. Acromegaly

Explanation: ***Hypothyroidism*** - Hypothyroidism is characterized by **insufficient thyroid hormone production** and is primarily regulated by the **pituitary-thyroid axis** involving TSH. - While growth hormone can indirectly affect thyroid function, it is not a direct cause of **primary hypothyroidism**. *Gigantism* - **Gigantism** is caused by **excessive growth hormone (GH) secretion** starting in childhood or adolescence before the epiphyseal growth plates have closed. - This leads to **abnormally increased linear growth** and overall body size. *Diabetes mellitus* - Growth hormone can induce **insulin resistance**, leading to **elevated blood glucose levels** and increased risk of developing **Type 2 Diabetes Mellitus**, especially in conditions of chronic GH excess like acromegaly. - This arises from GH's counter-regulatory effects on insulin action in peripheral tissues. *Acromegaly* - **Acromegaly** results from **excessive growth hormone (GH) secretion** in adulthood, after the epiphyseal growth plates have fused. - It causes **enlargement of hands, feet, and facial features**, as well as organomegaly, due to continued GH-stimulated tissue growth.

Practice by Chapter

Principles of Endocrine Regulation

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Hypothalamus and Pituitary Gland

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Thyroid Physiology

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Adrenal Cortex and Medulla

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Pancreatic Hormones and Glucose Metabolism

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Calcium and Phosphate Homeostasis

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Growth Hormone and Growth Factors

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Endocrine Regulation of Metabolism

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Hormone Receptors and Signaling

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Assessment of Endocrine Function

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