Endocrinology Practice Questions

Q: Oxytocin is synthesized in:

Hypothalamus. ***Hypothalamus*** - **Oxytocin** is a **neuropeptide hormone** primarily synthesized in the **magnocellular neurosecretory cells** of the **paraventricular** and **supraoptic nuclei** of the hypothalamus. - After synthesis, it is packed into vesicles and transported down the axons to the **posterior pituitary** for storage and release. *Posterior pituitary* - The **posterior pituitary gland** (neurohypophysis) is the site of **storage and release** of oxytocin, not its synthesis. - Once released from the posterior pituitary, oxytocin acts on target organs such as the **uterus during labor** and the **mammary glands during lactation**. *Anterior pituitary* - The **anterior pituitary gland** (adenohypophysis) synthesizes and secretes its own set of hormones, including **growth hormone**, **TSH**, **ACTH**, **FSH**, **LH**, and **prolactin**. - It does not play a direct role in the synthesis or storage of oxytocin. *Intermediate pituitary* - The **intermediate lobe** of the pituitary gland is rudimentary in humans and primarily produces hormones like **melanocyte-stimulating hormone (MSH)**. - It is not involved in the synthesis or storage of oxytocin.

Q: All of the following functions of vasopressin are mediated by V1 receptors, except

Water reabsorption. ***Water reabsorption*** - Vasopressin's effect on **water reabsorption** in the kidney collecting ducts is primarily mediated by **V2 receptors**. - **V2 receptors** activate a G protein-coupled signaling pathway leading to the insertion of **aquaporin-2 channels** into the apical membrane, increasing water permeability. *Vasoconstriction* - **Vasoconstriction** is a well-known function of vasopressin, mediated by its binding to **V1a receptors** (a subtype of V1 receptors) on vascular smooth muscle cells. - This activation leads to an increase in **intracellular calcium**, causing the muscle cells to contract and the blood vessels to narrow. *Smooth muscle contraction* - Vasopressin can induce **smooth muscle contraction** in various tissues, including the gastrointestinal tract and uterus, primarily through **V1 receptors**. - This effect is similar to its vasoconstrictor action, involving **calcium mobilization** and muscle fiber shortening. *None of the options* - This option is incorrect because **water reabsorption** is indeed mediated by V2 receptors, not V1 receptors. - The other functions listed (vasoconstriction and smooth muscle contraction) are correctly attributed to **V1 receptors**.

Q: A primigravida at 38 weeks of gestation has gone into labor. Oxytocin was started to augment labor. The second messenger system through which oxytocin acts is:

Phospholipase C (IP3/DAG pathway). ***Phospholipase C (IP3/DAG pathway)*** - Oxytocin binds to its receptor, which is a **Gq protein-coupled receptor**. This activates **phospholipase C**. - **Phospholipase C** then hydrolyzes **phosphatidylinositol 4,5-bisphosphate (PIP2)** into **inositol triphosphate (IP3)** and **diacylglycerol (DAG)**, which act as second messengers to increase intracellular calcium and mediate myometrial contraction. *Tyrosine kinase* - **Tyrosine kinase receptors** are typically activated by growth factors (e.g., insulin, epidermal growth factor) and lead to phosphorylation cascades. - This mechanism is not primarily associated with the downstream signaling of **oxytocin receptors**. *cGMP* - **Cyclic guanosine monophosphate (cGMP)** is a second messenger primarily involved in signaling pathways initiated by **nitric oxide** and some peptide hormones. - It often acts to cause smooth muscle relaxation, which is contrary to oxytocin's role in uterine contraction. *cAMP* - **Cyclic adenosine monophosphate (cAMP)** is a common second messenger for many hormones that bind to **Gs protein-coupled receptors**. - Hormones such as **epinephrine (beta-adrenergic receptors)** and **glucagon** utilize cAMP, typically leading to different cellular responses than those of oxytocin.

Q: Which protein secreted by adipocytes prevents obesity?

Leptin. ***Leptin*** - **Leptin** is a hormone secreted by **adipocytes** (fat cells) that plays a crucial role in long-term energy balance and appetite suppression. - It signals the brain about the body's energy stores, leading to decreased food intake and increased energy expenditure, and thus **preventing obesity**. *Galanin* - **Galanin** is a neuropeptide that has been shown to **stimulate food intake**, particularly fat consumption. - It is associated with **increased appetite** and **obesity**, rather than its prevention. *Neuropeptide Y* - **Neuropeptide Y (NPY)** is a potent **orexigenic** (appetite-stimulating) peptide primarily found in the hypothalamus. - Its activation leads to **increased food intake** and **decreased energy expenditure**, promoting weight gain and obesity. *Cathepsin* - **Cathepsins** are a family of **proteolytic enzymes** found in lysosomes. - They are involved in protein degradation and other cellular processes, but they are not directly involved in the prevention of obesity through appetite regulation or energy balance.

Q: Growth hormone secretion, true statement is:

Stimulated by exercise. ***Stimulated by exercise*** - **Exercise** is a potent physiological stimulus for **growth hormone (GH)** release, particularly during intense physical activity, due to mechanisms involving increased catecholamines and lactate. - This GH surge supports **muscle growth** and repair, and enhances fat metabolism. *Stimulated by somatostatin* - **Somatostatin** (also known as **growth hormone-inhibiting hormone**) *inhibits* the secretion of growth hormone from the anterior pituitary gland. - Its primary role is to provide a negative feedback loop to regulate GH levels. *Continuous secretion* - Growth hormone secretion is **pulsatile**, not continuous, with the largest bursts typically occurring during **sleep** (especially deep sleep). - Its release follows a **circadian rhythm** and is influenced by various physiological factors. *Stimulated by glucose* - High blood glucose levels (e.g., after a meal) tend to **inhibit** growth hormone secretion. - This is why an **oral glucose tolerance test** is used to diagnose **acromegaly** (excess GH), where GH levels fail to suppress appropriately.

Q: FSH and LH play an important role in the ovulatory cycle in females of reproductive age. They are produced from:

Adenohypophysis. ***Adenohypophysis*** - The **adenohypophysis**, also known as the **anterior pituitary gland**, is responsible for producing and secreting various hormones, including **follicle-stimulating hormone (FSH)** and **luteinizing hormone (LH)**. - These gonadotropins are crucial for regulating the **ovarian cycle**, promoting follicular development, ovulation, and corpus luteum formation. - FSH stimulates follicular growth and estrogen production, while LH triggers ovulation and promotes progesterone secretion from the corpus luteum. *Endometrium* - The **endometrium** is the inner lining of the uterus and undergoes cyclical changes in response to ovarian hormones (estrogen and progesterone), but it does not produce FSH or LH. - Its primary function is to provide an environment for embryo implantation and menstruation if pregnancy does not occur. *Corpus luteum* - The **corpus luteum** forms from the ruptured follicle after ovulation and primarily produces **progesterone** and some estrogen. - It plays a vital role in maintaining the uterine lining for potential pregnancy but does not produce FSH or LH. *Ovarian follicles* - **Ovarian follicles** contain the developing oocytes and produce **estrogen** as they grow. - While they are the target of FSH and LH, they do not produce these hormones themselves; instead, their growth and maturation are stimulated by FSH and LH.

Q: All are true about hormone functions except:

Cortisol regulates plasma volume. ***Cortisol regulates plasma volume*** - While cortisol plays a role in fluid balance by influencing **renal perfusion** and the action of other hormones like ADH, its primary role is not the direct regulation of plasma volume. - **Aldosterone** is the primary hormone directly responsible for regulating plasma volume through its effects on sodium and water reabsorption in the kidneys. *Thyroid hormones regulate metabolism* - **Thyroid hormones** (T3 and T4) are crucial for regulating the body's metabolic rate, influencing factors like energy production, protein synthesis, and cellular oxygen consumption. - They impact the metabolism of **carbohydrates, fats, and proteins**, affecting nearly every cell in the body. *ADH regulates blood osmolality* - **Antidiuretic hormone (ADH)**, also known as vasopressin, primarily regulates blood osmolality by controlling the reabsorption of water in the renal collecting ducts. - It increases the permeability of collecting ducts to water, thus concentrating urine and **reducing plasma osmolality** when it's high. *Insulin regulates blood glucose* - **Insulin** is a key hormone produced by the pancreas that regulates blood glucose levels by facilitating the uptake of glucose into cells for energy or storage. - It plays a crucial role in lowering blood glucose after meals by promoting **glucose utilization** and inhibiting glucose production by the liver.

Q: Organs involved in calcium homeostasis are all except

Lungs. ***Lungs*** - The **lungs** are primarily involved in gas exchange (oxygen and carbon dioxide) and do not play a direct role in the regulation of **calcium homeostasis**. - While other organs contribute to calcium balance through absorption, excretion, or hormone production, the lungs' physiological functions are unrelated to calcium metabolism. *Intestines* - The **intestines**, particularly the small intestine, are crucial for the **absorption of dietary calcium** under the influence of **active vitamin D**. - Without proper intestinal absorption, calcium levels in the body cannot be maintained. *Skin* - The **skin** is essential for the endogenous synthesis of **vitamin D3 (cholecalciferol)** when exposed to ultraviolet B (UVB) radiation. - This **vitamin D3** is then metabolized into active forms that regulate calcium and phosphate levels. *Kidneys* - The **kidneys** play a vital role in calcium homeostasis by **reabsorbing calcium** from the filtrate and excreting excess calcium. - They also hydroxylate calcidiol to form the active hormone **calcitriol** (1,25-dihydroxyvitamin D), which significantly influences calcium levels.

Q: Which of the following anterior pituitary hormones is primarily under inhibitory control of hypothalamus?

Prolactin. ***Prolactin*** - Prolactin secretion is primarily regulated by the **tonic inhibitory control of dopamine** (also known as prolactin-inhibiting hormone, PIH) from the hypothalamus. - Unlike other anterior pituitary hormones, the **absence of hypothalamic input leads to increased prolactin secretion**. *Growth Hormone (GH)* - GH secretion is primarily stimulated by **Growth Hormone-Releasing Hormone (GHRH)** from the hypothalamus and inhibited by **somatostatin** (also known as growth hormone-inhibiting hormone). The predominant control is stimulatory. - While somatostatin inhibits GH, the primary control of GH is considered **stimulatory via GHRH pulsatility**, not tonic inhibition as seen with prolactin. *TSH* - TSH secretion is primarily stimulated by **Thyrotropin-Releasing Hormone (TRH)** from the hypothalamus. - There is no significant tonic inhibitory control from the hypothalamus directly on TSH secretion; rather, it is subject to **negative feedback from thyroid hormones**. *LH and FSH* - Both LH and FSH secretion are primarily stimulated by **Gonadotropin-Releasing Hormone (GnRH)** from the hypothalamus. - GnRH is released in a **pulsatile manner** to stimulate the release of LH and FSH; there is no primary tonic inhibitory control from the hypothalamus.

Q: Increased ratio of insulin to glucagon causes

Hypoglycemia. ***Hypoglycemia*** - An increased insulin-to-glucagon ratio indicates **high insulin levels**, promoting glucose uptake and utilization by cells, which can lead to a drop in blood glucose below normal levels. - High insulin suppresses **hepatic glucose production** (gluconeogenesis and glycogenolysis) and stimulates **glycogenesis**, further lowering blood glucose. *Decreased amino acid synthesis* - **Insulin** is an **anabolic hormone** that promotes protein synthesis, including amino acid incorporation into proteins. - Therefore, an increased insulin-to-glucagon ratio would generally **increase**, not decrease, amino acid synthesis. *Decreased levels of lipoprotein lipase* - **Insulin enhances the activity and synthesis of lipoprotein lipase (LPL)**, particularly in adipose tissue. - This promotes the uptake of fatty acids from circulating lipoproteins into fat cells for storage. *Enhanced lipolysis in adipose tissue* - **Insulin inhibits lipolysis**, the breakdown of triglycerides into fatty acids and glycerol, in adipose tissue. - An increased insulin-to-glucagon ratio would therefore **suppress**, rather than enhance, lipolysis.

Question 1

Oxytocin is synthesized in:

Accepted Answer

Hypothalamus

Answer

Posterior pituitary

Answer

Anterior pituitary

Answer

Intermediate pituitary

Question 2

All of the following functions of vasopressin are mediated by V1 receptors, except

Accepted Answer

Water reabsorption

Answer

Vasoconstriction

Answer

Smooth muscle contraction

Answer

None of the options

Question 3

A primigravida at 38 weeks of gestation has gone into labor. Oxytocin was started to augment labor. The second messenger system through which oxytocin acts is:

Accepted Answer

Phospholipase C (IP3/DAG pathway)

Answer

Tyrosine kinase

Answer

cGMP

Answer

cAMP

Question 4

Which protein secreted by adipocytes prevents obesity?

Accepted Answer

Leptin

Answer

Galanin

Answer

Neuropeptide Y

Answer

Cathepsin

Question 5

Growth hormone secretion, true statement is:

Accepted Answer

Stimulated by exercise

Answer

Stimulated by somatostatin

Answer

Continuous secretion

Answer

Stimulated by glucose

Question 6

FSH and LH play an important role in the ovulatory cycle in females of reproductive age. They are produced from:

Accepted Answer

Adenohypophysis

Answer

Endometrium

Answer

Corpus luteum

Answer

Ovarian follicles

Question 7

All are true about hormone functions except:

Accepted Answer

Cortisol regulates plasma volume

Answer

Thyroid hormones regulate metabolism

Answer

ADH regulates blood osmolality

Answer

Insulin regulates blood glucose

Question 8

Organs involved in calcium homeostasis are all except

Accepted Answer

Lungs

Answer

Intestines

Answer

Skin

Answer

Kidneys

Question 9

Which of the following anterior pituitary hormones is primarily under inhibitory control of hypothalamus?

Accepted Answer

Prolactin

Answer

Growth Hormone (GH)

Answer

TSH

Answer

LH and FSH

Question 10

Increased ratio of insulin to glucagon causes

Accepted Answer

Hypoglycemia

Answer

Decreased amino acid synthesis

Answer

Decreased levels of lipoprotein lipase

Answer

Enhanced lipolysis in adipose tissue

Endocrinology — MCQs

Endocrinology — MCQs

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