Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 631: Which hormone does not increase in burns -

A. LH (Correct Answer)
B. Glucagon
C. Epinephrine
D. Cortisol

Explanation: ***LH*** - In severe burn injury, the **hypothalamic-pituitary-gonadal (HPG) axis** is typically suppressed, leading to decreased levels of gonadotropins like **Luteinizing Hormone (LH)** and Follicle-Stimulating Hormone (FSH). - This suppression is part of the overall stress response and can contribute to **gonadal dysfunction** in burn patients. *Glucagon* - **Glucagon** levels typically *increase* significantly after a burn injury due to the intense **stress response** and the need for increased glucose availability. - This hormone promotes **gluconeogenesis** and **glycogenolysis** to combat the hypermetabolic state induced by burns. *Epinephrine* - **Epinephrine** (adrenaline) is a key **catecholamine** released in large quantities following severe burns as part of the fight-or-flight response. - Its increase contributes to **tachycardia**, **vasoconstriction**, and the general **hypermetabolic state**. *Cortisol* - **Cortisol**, a primary stress hormone, is consistently *elevated* after burn injury. - It plays a crucial role in the **metabolic adaptations** to stress, including increasing **gluconeogenesis** and modulating the immune response.

Question 632: Receptors for thyroid hormones are present:

A. On the cell membrane
B. Inside the cells (Correct Answer)
C. In association with G-proteins
D. Across the cell membrane

Explanation: ***Inside the cells*** - Thyroid hormones are **lipophilic** and can easily pass through the cell membrane to bind with receptors located in the **cytoplasm or nucleus**. - These intracellular receptors then act as **transcription factors**, regulating gene expression. *On the cell membrane* - Receptors on the cell membrane are typically for **hydrophilic hormones** (e.g., peptide hormones) that cannot freely cross the lipid bilayer. - While there are some non-genomic effects mediated by cell surface receptors, the primary action of thyroid hormones is via intracellular receptors. *In association with G-proteins* - **G-protein coupled receptors** are cell membrane receptors that transduce signals through effector enzymes or ion channels, often for peptide or catecholamine hormones. - Thyroid hormones do not primarily signal through G-protein coupled receptors for their genomic effects. *Across the cell membrane* - This option refers to transmembrane proteins that span the entire cell membrane, which are characteristic of many cell surface receptors. - **Thyroid hormone receptors** are not transmembrane proteins but are found within the cell, often in the nucleus.

Question 633: Oxytocin causes all EXCEPT:

A. Milk ejection
B. Milk production (Correct Answer)
C. Induction of labour
D. Stimulates myoepithelial cells

Explanation: ***Milk production*** - **Oxytocin** is primarily involved in the **milk ejection reflex** (let-down), but prolactin is the hormone responsible for **milk synthesis** or production. - While oxytocin facilitates the release of milk already produced, it does not stimulate the **mammary glands** to produce more milk. *Milk ejection* - Oxytocin causes contraction of the **myoepithelial cells** surrounding the alveoli in the mammary glands, leading to the **ejection of milk** into the ducts. - This reflex is crucial for **breastfeeding** and is often stimulated by the suckling of an infant. *Induction of labour* - **Oxytocin** stimulates rhythmic contractions of the **uterine smooth muscle**, making it a key hormone for initiating and progressing **labor**. - It is often administered exogenously to **induce** or augment labor due to its **uterotonic effects**. *Stimulates myoepithelial cells* - Oxytocin directly acts on the **myoepithelial cells** within the breast to cause their contraction. - This contraction generates pressure that forces milk from the **alveoli** into the **lactiferous ducts**, leading to milk ejection.

Question 634: Iodine is transported to the thyroid gland by what?

A. Diffusion
B. Passive transport
C. Active transport (Correct Answer)
D. Pinocytosis

Explanation: ***Active transport*** - Iodine uptake by the thyroid gland, specifically by the **follicular cells**, is an **energy-dependent process** mediated by the sodium-iodide symporter (NIS). - This mechanism allows the thyroid to **concentrate iodide** against its electrochemical gradient, which is crucial for thyroid hormone synthesis. *Diffusion* - **Does not allow accumulation** of a substance against its concentration gradient, which is necessary for iodine uptake by the thyroid. - Would result in an equal distribution of iodine across the membrane, not the high intracellular concentrations observed in thyroid cells. *Passive transport* - Encompasses several mechanisms (like diffusion or facilitated diffusion) that **do not require metabolic energy**. - This broad category is incorrect because iodide transport into the thyroid gland specifically requires energy. *Pinocytosis* - A form of **endocytosis** where cells internalize liquids and small particles by engulfing them in vesicles. - While cells can internalize substances this way, it is not the primary or most efficient mechanism for transporting small ions like iodide into thyroid follicular cells.

Question 635: Oxytocin is synthesized in:

A. Posterior pituitary
B. Anterior pituitary
C. Intermediate pituitary
D. Hypothalamus (Correct Answer)

Explanation: ***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.

Question 636: 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:

A. Tyrosine kinase
B. Phospholipase C (IP3/DAG pathway) (Correct Answer)
C. cGMP
D. cAMP

Explanation: ***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.

Question 637: Growth hormone secretion, true statement is:

A. Stimulated by somatostatin
B. Continuous secretion
C. Stimulated by exercise (Correct Answer)
D. Stimulated by glucose

Explanation: ***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.

Question 638: FSH and LH play an important role in the ovulatory cycle in females of reproductive age. They are produced from:

A. Endometrium
B. Adenohypophysis (Correct Answer)
C. Corpus luteum
D. Ovarian follicles

Explanation: ***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.

Question 639: All are true about hormone functions except:

A. Cortisol regulates plasma volume (Correct Answer)
B. Thyroid hormones regulate metabolism
C. ADH regulates blood osmolality
D. Insulin regulates blood glucose

Explanation: ***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.

Question 640: Which of the following anterior pituitary hormones is primarily under inhibitory control of hypothalamus?

A. Growth Hormone (GH)
B. TSH
C. LH and FSH
D. Prolactin (Correct Answer)

Explanation: ***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.

Practice by Chapter

Principles of Endocrine Regulation

Practice Questions

Hypothalamus and Pituitary Gland

Practice Questions

Thyroid Physiology

Practice Questions

Adrenal Cortex and Medulla

Practice Questions

Pancreatic Hormones and Glucose Metabolism

Practice Questions

Calcium and Phosphate Homeostasis

Practice Questions

Growth Hormone and Growth Factors

Practice Questions

Endocrine Regulation of Metabolism

Practice Questions

Hormone Receptors and Signaling

Practice Questions

Assessment of Endocrine Function

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free