Endocrinology Practice Questions

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: Secretion of cortisol is highest at?

Early morning. ***Early morning*** - Cortisol secretion follows a **diurnal rhythm**, with the highest levels occurring in the early morning, typically between 6 AM and 9 AM. - This peak prepares the body for the metabolic demands of the upcoming day and is essential for maintaining **homeostasis**. *Midnight* - Cortisol levels are typically at their **lowest** during the middle of the night, reaching a nadir around midnight to 2 AM. - This low point is part of the normal **circadian rhythm** and allows for restorative sleep. *Afternoon* - Cortisol levels generally **decline throughout the day** after the morning peak, reaching lower but still measurable levels in the afternoon. - While not the lowest, afternoon levels are significantly reduced compared to the early morning. *Evening* - Cortisol secretion continues to **decrease** into the evening hours, contributing to the preparation for sleep. - Evening levels are considerably lower than morning levels, with the decline leading up to the nighttime nadir.

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: Insulin secretion is normally stimulated by ?

Glucagon-like peptide-1 (GLP-1). ***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.

Q: Insulin mediated glucose transport is seen in?

Adipose tissue. ***Adipose tissue*** - **Insulin** significantly stimulates glucose uptake into **adipose tissue** by promoting the translocation of **GLUT4 transporters** to the cell membrane. - This process is crucial for the storage of excess glucose as **triglycerides** in adipocytes. *Brain* - Glucose uptake into the brain is primarily **insulin-independent**, occurring via **GLUT1** and **GLUT3 transporters** found in the blood-brain barrier and neuronal membranes, respectively. - The brain relies on a constant, uninterrupted supply of glucose regardless of insulin levels. *RBC* - **Red blood cells (RBCs)** take up glucose via **insulin-independent GLUT1 transporters**. - Their metabolism is anaerobic, and they constantly require glucose but do not respond to insulin for uptake. *Kidney* - The **kidney** handles glucose primarily through glomerular filtration and reabsorption in the renal tubules, largely through **SGLT (sodium-glucose cotransporter)** and **GLUT transporters**. - While some glucose transport in the kidney is facilitated by GLUTs, glucose uptake by renal cells is largely **insulin-independent**.

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.

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 of the following acts via the tyrosine kinase receptor?

Insulin. ***Correct: Insulin*** - Insulin binds to its **tyrosine kinase receptor** on target cells, leading to autophosphorylation of the receptor and subsequent activation of intracellular signaling pathways. - This pathway is crucial for **glucose uptake** and metabolism, as well as protein synthesis and cell growth. - Insulin is the **classic example** of a hormone that uses the receptor tyrosine kinase (RTK) mechanism. *Incorrect: Thyroid-stimulating hormone (TSH)* - TSH acts primarily via a **G-protein coupled receptor (GPCR)**, which activates the adenylyl cyclase pathway to produce cAMP. - This mechanism is characteristic of hormones that mediate their effects through **second messengers** like cAMP, rather than direct phosphorylation. *Incorrect: Luteinizing hormone (LH)* - LH, like TSH, signals through a **G-protein coupled receptor (GPCR)** on its target cells (e.g., Leydig cells in males, theca and granulosa cells in females). - Its activation primarily leads to an increase in **cAMP** production, which then mediates its effects on steroidogenesis and gamete maturation. *Incorrect: Melanocyte-stimulating hormone (MSH)* - MSH binds to **melanocortin receptors (MCRs)**, which are also a type of **G-protein coupled receptor (GPCR)**. - Activation of these receptors primarily stimulates **cAMP pathways**, influencing melanin production and appetite regulation.

Question 1

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 2

Secretion of cortisol is highest at?

Accepted Answer

Early morning

Answer

Afternoon

Answer

Evening

Answer

Midnight

Question 3

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 4

Growth hormone has its effect on growth through?

Accepted Answer

IGF-1

Answer

Directly

Answer

Thyroxine

Answer

Intranuclear receptors

Question 5

Insulin secretion is normally stimulated by ?

Accepted Answer

Glucagon-like peptide-1 (GLP-1)

Answer

Vasoactive intestinal peptide (VIP)

Answer

Alpha-adrenergic receptors

Answer

Peptide YY (PYY)

Question 6

Insulin mediated glucose transport is seen in?

Accepted Answer

Adipose tissue

Answer

Brain

Answer

RBC

Answer

Kidney

Question 7

Which hormone stimulates the thyroid gland during pregnancy?

Accepted Answer

HCG

Answer

Human placental lactogen

Answer

ACTH

Answer

Prolactin

Question 8

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

Accepted Answer

Hypothyroidism

Answer

Diabetes mellitus

Answer

Gigantism

Answer

Acromegaly

Question 9

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

Accepted Answer

Estrogen

Answer

Progesterone

Answer

Cortisol

Answer

Aldosterone

Question 10

Which of the following acts via the tyrosine kinase receptor?

Accepted Answer

Insulin

Answer

Thyroid-stimulating hormone (TSH)

Answer

Luteinizing hormone (LH)

Answer

Melanocyte-stimulating hormone (MSH)

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?