Endocrinology Practice Questions

Q: Which of the following hormones has its release inhibited by thyroxine?

TSH. ***TSH*** - **Thyroid-stimulating hormone (TSH)** release from the anterior pituitary is **inhibited by thyroxine** (T4) through a negative feedback loop. - When **thyroxine levels are high**, they signal the pituitary to produce less TSH. *LH* - **Luteinizing hormone (LH)** is primarily regulated by **gonadotropin-releasing hormone (GnRH)** and inhibited by sex steroids (estrogen, progesterone, testosterone), not directly by thyroxine. - Imbalances in thyroid hormones can indirectly affect LH, but **thyroxine does not directly inhibit its release**. *GH* - **Growth hormone (GH)** secretion is regulated by **growth hormone-releasing hormone (GHRH)** and **somatostatin**, as well as other factors like IGF-1. - While thyroid hormones can indirectly influence GH secretion, **thyroxine does not directly inhibit GH release**. *PRL* - **Prolactin (PRL)** release is primarily inhibited by **dopamine** from the hypothalamus. - Although hypothyroidism can sometimes lead to hyperprolactinemia, **thyroxine does not directly inhibit prolactin release**.

Q: Ghrelin stimulates the release of which hormone?

Growth hormone. ***Growth hormone*** - **Ghrelin** is a **neuropeptide** that acts as a potent **growth hormone-releasing peptide (GHRP)**. - It stimulates **growth hormone (GH)** secretion from the anterior pituitary, primarily by acting on the **growth hormone secretagogue receptor (GHS-R)** in the hypothalamus and pituitary. *LH* - **Luteinizing hormone (LH)** release is primarily stimulated by **gonadotropin-releasing hormone (GnRH)**, not ghrelin. - While ghrelin can have some modulatory effects on reproductive hormones, its primary role is not the direct stimulation of LH. *PTH* - **Parathyroid hormone (PTH)** is released in response to **low serum calcium levels**, acting to raise calcium levels. - Ghrelin has no direct established role in stimulating PTH secretion. *Prolactin* - **Prolactin** release is primarily regulated by the inhibition of **dopamine** from the hypothalamus. - Although ghrelin has been shown to a minor extent to stimulate prolactin, growth hormone is the main hormone that ghrelin stimulates.

Q: Aldosterone is produced by which of the following?

Adrenal gland. ***Adrenal gland*** - Aldosterone is a **mineralocorticoid hormone** primarily produced by the **zona glomerulosa** of the **adrenal cortex**, which is the outer layer of the adrenal gland. - Its main role is to regulate **sodium and potassium balance** and thereby influence blood pressure. *Posterior pituitary gland* - The posterior pituitary gland stores and releases **oxytocin** and **antidiuretic hormone (ADH)**, which are produced by the hypothalamus. - It does not synthesize its own hormones, and specifically, it does not produce aldosterone. *Hypothalamus* - The hypothalamus produces various **releasing and inhibiting hormones** that control the anterior pituitary, as well as ADH and oxytocin which are transported to the posterior pituitary. - While it plays a role in regulating many endocrine functions, it does not directly produce aldosterone. *Anterior pituitary gland* - The anterior pituitary gland produces several hormones, including **growth hormone**, **prolactin**, **thyroid-stimulating hormone (TSH)**, **adrenocorticotropic hormone (ACTH)**, **follicle-stimulating hormone (FSH)**, and **luteinizing hormone (LH)**. - Aldosterone production is not among its functions, although ACTH from the anterior pituitary can indirectly influence aldosterone synthesis.

Q: Which is the true statement about Anterior Pituitary Hormones?

Secretion of anterior pituitary hormones is pulsatile. ***Secretion of anterior pituitary hormones is pulsatile*** - The **anterior pituitary** releases its hormones in a **pulsatile fashion**, meaning in bursts rather than a continuous stream. - This pulsatile secretion is crucial for maintaining the sensitivity of target tissues and for proper endocrine regulation. *The hypophyseal portal veins are associated with the posterior lobe of the pituitary gland.* - The **hypophyseal portal veins** are part of the **hypothalamic-hypophyseal portal system**, which primarily regulates the **anterior pituitary gland**. - The **posterior pituitary** is regulated by direct neural connections from the hypothalamus, not by a portal venous system. *No hormones are secreted before 28 weeks of gestation except prolactin* - Several **anterior pituitary hormones**, including **growth hormone**, **TSH**, and **ACTH**, are secreted much earlier in gestation, typically by the end of the first trimester. - While **prolactin** is also secreted early, it is not the *only* anterior pituitary hormone produced before 28 weeks. *Most of the pituitary hormones are secreted by the posterior lobe* - The **anterior pituitary** (adenohypophysis) is responsible for secreting most of the pituitary hormones, including **GH, TSH, ACTH, FSH, LH, and prolactin**. - The **posterior pituitary** (neurohypophysis) only releases two hormones: **oxytocin** and **antidiuretic hormone (ADH)**, which are produced in the hypothalamus.

Q: On insulin administration, what change is expected in the extracellular fluid (ECF)?

Hypoglycemia. **Hypoglycemia (Correct Answer)** - Insulin promotes the uptake of **glucose** from the ECF into cells, primarily muscle and adipose tissue - This action leads to a decrease in ECF **glucose concentration**, resulting in **hypoglycemia** if insulin levels are excessive or glucose intake is insufficient - This is the primary and most significant change in ECF composition after insulin administration *Hyperkalemia (Incorrect)* - Insulin actually stimulates the cellular uptake of **potassium**, moving it from the ECF into the intracellular fluid - Therefore, insulin administration typically causes **hypokalemia**, not hyperkalemia - This effect is sometimes used therapeutically to treat hyperkalemia by driving potassium into cells *Hyponatremia (Incorrect)* - Insulin primarily affects **glucose** and **potassium** metabolism and does not directly cause changes in sodium concentration in the ECF - **Hyponatremia** would be more associated with altered water balance or disorders of kidney function, not direct insulin effects - Sodium homeostasis is regulated by the renin-angiotensin-aldosterone system and ADH *Hypocalcemia (Incorrect)* - Insulin has no direct effect on **calcium** levels or its regulation in the ECF - **Calcium homeostasis** is primarily regulated by parathyroid hormone (PTH), vitamin D, and calcitonin, independent of insulin action - Changes in calcium concentration are not expected with insulin administration

Q: Substrate-controlled hormone is

Glucagon. ***Glucagon*** - **Glucagon** secretion is primarily regulated by **blood glucose levels**. When blood glucose is low, glucagon is released to increase it. - This direct response to a metabolite concentration (glucose, a substrate) makes it a **substrate-controlled hormone**. *LH* - **Luteinizing hormone (LH)** is a gonadotropin secreted by the anterior pituitary, controlled by **GnRH** from the hypothalamus and feedback from gonadal steroids. - It is part of a complex **neuroendocrine axis**, not directly regulated by a metabolic substrate. *TRH* - **Thyrotropin-releasing hormone (TRH)** is a neurohormone produced in the hypothalamus that stimulates the pituitary to release TSH. - Its release is primarily controlled by **negative feedback** from thyroid hormones and environmental factors, not by a specific metabolic substrate. *FSH* - **Follicle-stimulating hormone (FSH)** is also a gonadotropin, like LH, regulated by **GnRH** and gonadal feedback. - Its regulation involves the **hypothalamic-pituitary-gonadal axis**, not direct substrate control.

Q: True about oxytocin are all except

Synthesized by anterior pituitary. ***Synthesized by anterior pituitary*** - Oxytocin is **synthesized in the hypothalamus** (specifically in the paraventricular and supraoptic nuclei), not in the anterior pituitary. - The **anterior pituitary** produces different hormones like **FSH, LH, ACTH, TSH, prolactin, and growth hormone**, but does not synthesize oxytocin. *Causes contraction of upper segment* - Oxytocin does cause **contractions of the upper uterine segment** as part of coordinated uterine activity during labor. - This contributes to **fundal dominance** where contractions are strongest at the fundus and weaken toward the cervix. *Causes uterine contraction of body* - Oxytocin stimulates **rhythmic contractions of the myometrium** throughout the uterine body during labor. - These **coordinated contractions** are essential for effective cervical dilation and fetal expulsion. *Secreted by posterior pituitary* - Oxytocin is indeed **stored and released by the posterior pituitary** after being transported from the hypothalamus. - The posterior pituitary acts as a **storage and release site** for both oxytocin and **antidiuretic hormone (ADH)**.

Q: Which of the following uses cGMP as a second messenger?

Atrial natriuretic peptide. ***Atrial natriuretic peptide*** - **Atrial natriuretic peptide (ANP)** primarily uses **cGMP** as its second messenger to exert its effects on the cardiovascular system and kidneys. - ANP binds to its receptor, activating **guanylate cyclase**, which then converts **GTP to cGMP**, leading to vasodilation and natriuresis. *Cortisone* - **Cortisone** is a **glucocorticoid** that primarily functions by binding to intracellular **steroid hormone receptors**, which then translocate to the nucleus to regulate gene expression. - It does not utilize cGMP as a second messenger; its signaling pathway involves direct gene transcription modulation. *GH* - **Growth hormone (GH)** typically signals through the **JAK/STAT pathway** upon binding to its receptor, leading to the phosphorylation of STAT proteins and subsequent gene transcription. - GH primarily stimulates cell growth and metabolism through tyrosine kinase-associated receptors, not via cGMP. *Thyroxine* - **Thyroxine (T4)** and its active form **triiodothyronine (T3)** are **thyroid hormones** that bind to nuclear receptors, influencing gene expression directly. - Their mechanism of action involves altering protein synthesis, and they do not use cGMP as a second messenger.

Question 1

Which of the following hormones has its release inhibited by thyroxine?

Accepted Answer

TSH

Answer

LH

Answer

GH

Answer

PRL

Question 2

Ghrelin stimulates the release of which hormone?

Accepted Answer

Growth hormone

Answer

LH

Answer

PTH

Answer

Prolactin

Question 3

Aldosterone is produced by which of the following?

Accepted Answer

Adrenal gland

Answer

Posterior pituitary gland

Answer

Hypothalamus

Answer

Anterior pituitary gland

Question 4

Which is the single most important factor that stimulates insulin secretion?

Accepted Answer

Increased plasma glucose concentration stimulates insulin release.

Answer

Increased plasma potassium concentration stimulates insulin release.

Answer

Increased plasma fatty acid concentration stimulates insulin release.

Answer

Increased amino acid concentration stimulates insulin release.

Question 5

Estrogen action on carbohydrate metabolism:

Accepted Answer

Increases uptake of glucose through increase in insulin sensitivity

Answer

Glycolysis increases

Answer

Increasing central adipose deposition

Answer

Worsening of NIDDM

Question 6

Which is the true statement about Anterior Pituitary Hormones?

Accepted Answer

Secretion of anterior pituitary hormones is pulsatile

Answer

The hypophyseal portal veins are associated with the posterior lobe of the pituitary gland.

Answer

No hormones are secreted before 28 weeks of gestation except prolactin

Answer

Most of the pituitary hormones are secreted by the posterior lobe

Question 7

On insulin administration, what change is expected in the extracellular fluid (ECF)?

Accepted Answer

Hypoglycemia

Answer

Hyperkalemia

Answer

Hyponatremia

Answer

Hypocalcemia

Question 8

Substrate-controlled hormone is

Accepted Answer

Glucagon

Answer

LH

Answer

TRH

Answer

FSH

Question 9

True about oxytocin are all except

Accepted Answer

Synthesized by anterior pituitary

Answer

Causes contraction of upper segment

Answer

Causes uterine contraction of body

Answer

Secreted by posterior pituitary

Question 10

Which of the following uses cGMP as a second messenger?

Accepted Answer

Atrial natriuretic peptide

Answer

Cortisone

Answer

GH

Answer

Thyroxine

Endocrinology — MCQs

Endocrinology — MCQs

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