Endocrinology Practice Questions

Q: Which hormone does not increase in burns -

LH. ***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.

Q: Receptors for thyroid hormones are present:

Inside the cells. ***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.

Q: Oxytocin causes all EXCEPT:

Milk production. ***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.

Q: Iodine is transported to the thyroid gland by what?

Active transport. ***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.

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.

Question 1

Which hormone does not increase in burns -

Accepted Answer

LH

Answer

Glucagon

Answer

Epinephrine

Answer

Cortisol

Question 2

Receptors for thyroid hormones are present:

Accepted Answer

Inside the cells

Answer

On the cell membrane

Answer

In association with G-proteins

Answer

Across the cell membrane

Question 3

Oxytocin causes all EXCEPT:

Accepted Answer

Milk production

Answer

Milk ejection

Answer

Induction of labour

Answer

Stimulates myoepithelial cells

Question 4

Iodine is transported to the thyroid gland by what?

Accepted Answer

Active transport

Answer

Diffusion

Answer

Passive transport

Answer

Pinocytosis

Question 5

Oxytocin is synthesized in:

Accepted Answer

Hypothalamus

Answer

Posterior pituitary

Answer

Anterior pituitary

Answer

Intermediate pituitary

Question 6

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 7

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 8

Which protein secreted by adipocytes prevents obesity?

Accepted Answer

Leptin

Answer

Galanin

Answer

Neuropeptide Y

Answer

Cathepsin

Question 9

Growth hormone secretion, true statement is:

Accepted Answer

Stimulated by exercise

Answer

Stimulated by somatostatin

Answer

Continuous secretion

Answer

Stimulated by glucose

Question 10

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

Endocrinology — MCQs

Endocrinology — MCQs

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