Endocrinology Practice Questions

Q: What hormone is primarily responsible for triggering the LH surge?

Estrogen. ***Estrogen*** - As the dominant follicle matures, it produces increasing amounts of **estrogen**, primarily **estradiol**. - When **estradiol** levels reach a critical threshold, it switches from negative to positive feedback on the hypothalamus and anterior pituitary, leading to the **LH surge**. *Anti-Mullerian Hormone (AMH)* - **AMH** is produced by granulosa cells of small antral follicles and is a marker of **ovarian reserve**. - It plays a role in regulating follicular development but is not directly responsible for initiating the **LH surge**. *Follicle-Stimulating Hormone (FSH)* - **FSH** stimulates the growth and development of ovarian follicles, which in turn produce estrogen. - While essential for follicular development, the surge is not triggered by FSH itself but rather by the high **estrogen** levels resulting from FSH action. *Progesterone* - **Progesterone** levels rise significantly **after** the LH surge and ovulation, primarily from the corpus luteum, to prepare the uterus for implantation. - It acts to inhibit further LH and FSH release and is not the primary trigger for the initial **LH surge**.

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

10-12 weeks. ***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**.

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

2 weeks. ***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.

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

ACTH stimulates cortisol secretion from the adrenal glands.. ***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.

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

Insulin. ***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.

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

Increase appetite. ***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.

Q: Growth hormone has its effect on growth through?

IGF-1. ***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.

Q: The PRIMARY inhibitor of FSH and LH through negative feedback mechanism is?

Estrogen. ***Estrogen*** - **Estrogen**, particularly estradiol, exerts a **negative feedback** effect on the hypothalamus and anterior pituitary gland, reducing the release of **GnRH**, and subsequently **both FSH and LH**. - This mechanism operates throughout most of the menstrual cycle and is essential for regulating follicular development. - Among the given options, estrogen is the primary inhibitor affecting **both** FSH and LH simultaneously. - **Note:** Inhibin (not listed) is the most potent specific inhibitor of FSH secretion from the pituitary. *Progesterone* - **Progesterone** exerts negative feedback primarily during the **luteal phase** and pregnancy. - It predominantly suppresses **LH** secretion and has a lesser effect on FSH compared to estrogen. - While physiologically important, it is not the primary inhibitor when considering regulation of both FSH and LH together. *Cortisol* - **Cortisol** is a glucocorticoid involved in **stress response**, metabolism, and immune function. - High cortisol levels can indirectly suppress the reproductive axis (stress-induced hypogonadism), but this is not a primary physiological regulatory mechanism. - It is not part of the normal negative feedback control of FSH and LH. *Aldosterone* - **Aldosterone** is a mineralocorticoid regulating **sodium and potassium balance** in the kidneys. - It has no role in the hypothalamic-pituitary-gonadal axis or negative feedback regulation of FSH and LH.

Q: Which hormone stimulates the thyroid gland during pregnancy?

HCG. **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.

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

Hypothyroidism. ***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.

Question 1

What hormone is primarily responsible for triggering the LH surge?

Accepted Answer

Estrogen

Answer

Anti-Mullerian Hormone (AMH)

Answer

Follicle-Stimulating Hormone (FSH)

Answer

Progesterone

Question 2

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

Accepted Answer

10-12 weeks

Answer

6-7 weeks

Answer

7-8 weeks

Answer

12-14 weeks

Question 3

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

Accepted Answer

2 weeks

Answer

1 week

Answer

3 weeks

Answer

4 weeks

Question 4

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

Accepted Answer

ACTH stimulates cortisol secretion from the adrenal glands.

Answer

Cortisol secretion follows a diurnal rhythm, peaking in the morning.

Answer

ACTH primarily regulates glucocorticoid secretion, not mineralocorticoid secretion.

Answer

ACTH is derived from proopiomelanocortin (POMC), but this is unrelated to cortisol secretion.

Question 5

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

Accepted Answer

Insulin

Answer

GH

Answer

Thyroxine

Answer

Estrogen

Question 6

What is the primary function of Ghrelin in the human body?

Accepted Answer

Increase appetite

Answer

Stimulate water absorption

Answer

Regulation of temperature

Answer

Stimulate lipogenesis

Question 7

Growth hormone has its effect on growth through?

Accepted Answer

IGF-1

Answer

Directly

Answer

Thyroxine

Answer

Intranuclear receptors

Question 8

The PRIMARY inhibitor of FSH and LH through negative feedback mechanism is?

Accepted Answer

Estrogen

Answer

Progesterone

Answer

Cortisol

Answer

Aldosterone

Question 9

Which hormone stimulates the thyroid gland during pregnancy?

Accepted Answer

HCG

Answer

Human placental lactogen

Answer

ACTH

Answer

Prolactin

Question 10

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

Accepted Answer

Hypothyroidism

Answer

Diabetes mellitus

Answer

Gigantism

Answer

Acromegaly

Endocrinology — MCQs

Endocrinology — MCQs

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