Endocrinology Practice Questions

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: 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: 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: Among the following, prolactin secretion is maximum:

24 hrs after delivery. ***Correct: 24 hrs after delivery*** - Prolactin levels are highest in the initial **24 hours postpartum**, especially during and after **breastfeeding sessions**, which act as a powerful stimulus for prolactin release. - This peak prolactin level is crucial for initiating and maintaining **lactation** following childbirth. - The postpartum prolactin surge represents the **maximum physiological level** of this hormone under normal circumstances. *Incorrect: During REM sleep* - While prolactin secretion does exhibit a **circadian rhythm** with nocturnal peaks, the highest levels do not specifically occur during **REM sleep**; rather, they are elevated throughout the sleep cycle. - Though prolactin does rise during sleep, the magnitudes are **not comparable** to the surges seen postpartum or after intense suckling. *Incorrect: After 2 hours of running* - Exercise, particularly prolonged and intense physical activity, can cause a transient increase in prolactin levels due to **stress response** and hormonal changes. - However, this exercise-induced increase is generally **modest** compared to the physiological surge observed after delivery. *Incorrect: 24 hours after ovulation* - Prolactin levels show a slight increase during the **luteal phase** of the menstrual cycle, which follows ovulation, primarily due to rising progesterone levels. - This elevation is significantly **lower** than the dramatic rise seen immediately postpartum needed for milk production.

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.

Q: Which of the following is the MOST CHARACTERISTIC metabolic feature of type 1 diabetes mellitus?

Increased lipolysis. ***Increased lipolysis*** - Due to **absolute insulin deficiency** in type 1 diabetes, the body cannot properly utilize glucose, leading to a shift toward **fat metabolism** for energy. - This results in increased breakdown of **triglycerides** into **fatty acids** and **glycerol**, which are then converted to **ketone bodies** in the liver. - **Ketoacidosis** resulting from increased lipolysis is the most **characteristic and distinguishing** metabolic feature of type 1 diabetes, differentiating it from type 2 diabetes. *Decreased glucose uptake* - Decreased glucose uptake by insulin-sensitive tissues (muscle and adipose tissue) is the **primary metabolic defect** in type 1 diabetes due to the absolute lack of insulin. - While this is fundamental to the pathophysiology, it occurs in **both type 1 and type 2 diabetes**, making it less characteristic of type 1 specifically. *Increased hepatic glucose output* - Increased hepatic glucose output (via gluconeogenesis and glycogenolysis) is a prominent feature due to loss of insulin's suppressive effects on the liver. - However, this also occurs in **type 2 diabetes** and is not as distinctive as the dramatic shift to lipolysis and ketone production seen in type 1. *Increased protein catabolism* - While protein catabolism is increased in type 1 diabetes, contributing to **muscle wasting** and providing substrates for gluconeogenesis, it is a less immediate and less specific feature. - The metabolic shift to **lipolysis and ketogenesis** is more rapid, more clinically significant, and more characteristic of the type 1 diabetic state.

Q: Aldosterone synthesis is stimulated by which of the following?

High potassium levels (Hyperkalemia). ***High potassium levels (Hyperkalemia)*** - Elevated **potassium levels** directly stimulate the **zona glomerulosa** cells of the adrenal cortex to synthesize and release **aldosterone**. - This is a **potent and sustained** stimulus - even a small increase in serum potassium (0.1 mEq/L) can significantly increase aldosterone secretion. - This is a crucial homeostatic mechanism to promote potassium excretion and maintain **potassium balance**. *Stimulation by ACTH (Adrenocorticotropic hormone)* - ACTH does have a **stimulatory effect** on aldosterone synthesis, but this effect is **transient and minor** compared to the effects of hyperkalemia and angiotensin II. - ACTH plays a **permissive role** - it is necessary for maintaining the structural and functional integrity of the zona glomerulosa, but is not a primary regulator of aldosterone secretion. - Chronic regulation of aldosterone is primarily controlled by the **renin-angiotensin-aldosterone system (RAAS)** and **serum potassium levels**, not ACTH. - In conditions like ACTH deficiency, some aldosterone production continues due to intact RAAS and potassium regulation. *High sodium levels (Hypernatremia)* - **High sodium levels** actually tend to **inhibit aldosterone secretion**, as aldosterone's primary action is to promote sodium reabsorption. - The body aims to excrete excess sodium when hypernatremic, which is generally achieved by decreased aldosterone and increased **atrial natriuretic peptide (ANP)**. *Use of exogenous steroids* - **Exogenous steroids** (like glucocorticoids) can suppress the **hypothalamic-pituitary-adrenal (HPA) axis**, thereby reducing the endogenous production of all adrenal hormones, including aldosterone. - This can lead to **adrenal insufficiency** if exogenous steroids are stopped abruptly.

Q: Insulin-like growth factor is secreted by:

Liver. ***Liver*** - The **liver** is the primary site of **insulin-like growth factor 1 (IGF-1)** production in response to **growth hormone (GH)** stimulation. - IGF-1 mediates many of the growth-promoting effects of GH, affecting various tissues throughout the body. *Pituitary gland* - The **pituitary gland** secretes **growth hormone (GH)**, which then stimulates the liver to produce IGF-1, but it does not directly secrete IGF-1. - Its role is upstream in the GH-IGF-1 axis, initiating the signaling cascade. *Pancreas* - The **pancreas** is primarily known for secreting **insulin** and **glucagon**, which regulate blood glucose levels. - It does not produce significant amounts of IGF-1. *Adrenal glands* - The **adrenal glands** produce hormones like **cortisol**, **aldosterone**, and **androgens**. - They are not involved in the direct secretion of IGF-1.

Q: Osteoclasts have all of the following functions except -

Receptor for parathormone. ***Receptor for parathormone*** - **Osteoclasts** do not directly have receptors for **parathormone (PTH)**; instead, **osteoblasts** have PTH receptors. - When PTH binds to osteoblasts, they release factors (like **RANKL**) that stimulate osteoclast activity, thus indirectly regulating bone resorption. *Bone resorption* - **Osteoclasts** are specialized cells primarily responsible for **resorbing bone matrix**, a critical process in bone remodeling. - They secrete **acids and enzymes** to break down the mineral and organic components of bone. *Ruffled border* - The **ruffled border** is a characteristic morphological feature of active osteoclasts, representing a highly folded plasma membrane. - This specialized structure increases the surface area for the secretion of **protons and lysosomal enzymes** into the bone-resorbing compartment. *RANK ligand production* - **Osteoclasts** do not produce **RANK ligand (RANKL)**; rather, they have **RANK receptors** that bind to RANKL produced by **osteoblasts and stromal cells**. - The binding of RANKL to RANK is essential for the **differentiation, activation, and survival** of osteoclasts.

Q: During pregnancy, the increased size of the pituitary gland is primarily due to the enlargement of which hormone-secreting cells?

Prolactin. ***Prolactin*** - During pregnancy, the number and size of **lactotrophs**, the cells that secrete prolactin, increase significantly due to high **estrogen** levels. - This **hyperplasia** and **hypertrophy** of lactotrophs contribute to the overall enlargement of the pituitary gland, preparing it for lactation. *Growth hormone* - While growth hormone is important, there isn't a primary enlargement of **somatotrophs** (GH-secreting cells) in the pituitary during pregnancy. - Furthermore, most circulating GH during pregnancy is **placental growth hormone**, rather than pituitary-derived. *ACTH* - Adrenocorticotropic hormone (ACTH) is secreted by **corticotrophs**, and these cells do not undergo prominent hypertrophy or hyperplasia during normal pregnancy. - While cortisol levels increase, this is largely due to factors other than increased pituitary ACTH cell size. *TSH* - Thyroid-stimulating hormone (TSH) is secreted by **thyrotrophs**, which do not notably enlarge during pregnancy. - Thyroid gland activity increases during pregnancy, but this is mediated by **hCG** and other mechanisms, not pituitary thyrotroph growth.

Question 1

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

Accepted Answer

Estrogen

Answer

Progesterone

Answer

Cortisol

Answer

Aldosterone

Question 2

Growth hormone has its effect on growth through?

Accepted Answer

IGF-1

Answer

Directly

Answer

Thyroxine

Answer

Intranuclear receptors

Question 3

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

Accepted Answer

Hypothyroidism

Answer

Diabetes mellitus

Answer

Gigantism

Answer

Acromegaly

Question 4

Among the following, prolactin secretion is maximum:

Accepted Answer

24 hrs after delivery

Answer

During REM sleep

Answer

After 2 hours of running

Answer

24 hours after ovulation

Question 5

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)

Question 6

Which of the following is the MOST CHARACTERISTIC metabolic feature of type 1 diabetes mellitus?

Accepted Answer

Increased lipolysis

Answer

Increased protein catabolism

Answer

Increased hepatic glucose output

Answer

Decreased glucose uptake

Question 7

Aldosterone synthesis is stimulated by which of the following?

Accepted Answer

High potassium levels (Hyperkalemia)

Answer

High sodium levels (Hypernatremia)

Answer

Use of exogenous steroids

Answer

Stimulation by ACTH (Adrenocorticotropic hormone)

Question 8

Insulin-like growth factor is secreted by:

Accepted Answer

Liver

Answer

Pituitary gland

Answer

Pancreas

Answer

Adrenal glands

Question 9

Osteoclasts have all of the following functions except -

Accepted Answer

Receptor for parathormone

Answer

Ruffled border

Answer

Bone resorption

Answer

RANK ligand production

Question 10

During pregnancy, the increased size of the pituitary gland is primarily due to the enlargement of which hormone-secreting cells?

Accepted Answer

Prolactin

Answer

Growth hormone

Answer

ACTH

Answer

TSH

Endocrinology — MCQs

Endocrinology — MCQs

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