Endocrinology Practice Questions

Q: Leptin is secreted by?

Adipose tissue. ***Adipose tissue*** - **Leptin** is a hormone primarily produced by **adipocytes** (fat cells) in adipose tissue. - Its main role is to regulate **energy balance** by signaling satiety to the brain, thereby reducing appetite and promoting energy expenditure. *Ovaries* - Ovaries primarily secrete **sex hormones** like **estrogen** and **progesterone**, which are crucial for female reproductive function. - While they play a role in metabolism, they are not the primary source of leptin. *Hypothalamus* - The **hypothalamus** is a region of the brain that **responds to leptin** and regulates many bodily functions, including appetite and metabolism, but it does not secrete leptin. - It integrates signals like leptin to maintain **homeostasis**. *Liver* - The liver is a central metabolic organ, involved in processes such as **glucose regulation**, protein synthesis, and detoxification. - While it produces many hormones and proteins, **leptin synthesis** is not one of its primary endocrine functions.

Q: Which one is an example of short loop negative feedback mechanism?

TSH inhibiting TRH release from hypothalamus. ***TSH inhibiting TRH release from hypothalamus*** - This is the **classic example of short-loop negative feedback** - **Short-loop feedback** occurs when a **pituitary hormone (TSH)** acts directly on the **hypothalamus** to inhibit the release of its corresponding **releasing hormone (TRH)** - This represents a **direct feedback** from the **anterior pituitary** back to the **hypothalamus** - **Key feature**: Involves only **two levels** of the endocrine axis (pituitary and hypothalamus) *TRH inhibiting its release from hypothalamus* - This describes **ultra-short loop (autocrine) feedback**, not short-loop feedback - In this mechanism, the **releasing hormone inhibits its own secretion** from the same cells - This is a **very localized, autocrine mechanism** rather than a true short-loop feedback - **Short-loop feedback** specifically requires a **pituitary hormone** acting back on the hypothalamus *T3, T4 inhibiting TRH release from hypothalamus* - This is an example of **long-loop negative feedback** - The **final hormone products (T3, T4)** from the **thyroid gland** inhibit the release of **TRH** from the **hypothalamus** - This feedback loop involves **three levels**: peripheral endocrine gland (thyroid), pituitary, and hypothalamus - **Key feature**: The **target organ hormone** feeds back to control higher centers *T3, T4 inhibiting TSH release from anterior pituitary* - This is another example of **long-loop negative feedback** - The **final hormone products (T3, T4)** from the **thyroid gland** inhibit **TSH** release from the **anterior pituitary** - This represents the **primary long-loop feedback** in the hypothalamic-pituitary-thyroid axis - This is the **most clinically significant feedback mechanism** in thyroid regulation

Q: What is the characteristic hormone pattern in hypergonadotropic hypogonadism?

Increase FSH increase LH. ***Increase FSH increase LH*** - **Hypergonadotropic hypogonadism** indicates primary gonadal failure, meaning the gonads (testes or ovaries) are not producing enough sex hormones (testosterone or estrogen). - The pituitary gland, recognizing the low sex hormone levels, compensates by increasing the production of **follicle-stimulating hormone (FSH)** and **luteinizing hormone (LH)** to stimulate the dysfunctional gonads [1]. *Decrease FSH and increase LH* - A decrease in FSH and an increase in LH is not a typical pattern for primary hypogonadism and could suggest a different endocrine disorder or a transient fluctuation. - This pattern is more commonly seen in conditions like **polycystic ovary syndrome (PCOS)** in women, where the LH/FSH ratio is elevated [2]. *Decrease FSH and LH* - A decrease in both FSH and LH indicates **hypogonadotropic hypogonadism**, which is secondary hypogonadism caused by dysfunction at the level of the pituitary gland or hypothalamus [2]. - In this scenario, the pituitary is not producing enough gonadotropins to stimulate the gonads, leading to low sex hormone levels. *Increase FSH decrease LH* - An isolated increase in FSH with a decrease in LH is an unusual pattern for most common forms of hypogonadism. - While FSH can sometimes be preferentially elevated in early stages of gonadal failure, a decrease in LH would be contradictory to the compensatory mechanism of the pituitary in hypergonadotropic hypogonadism.

Q: All of the following are increased in Acute stress except

Insulin. ***Insulin*** - During acute stress, **insulin secretion is actively suppressed** by catecholamines (epinephrine and norepinephrine) acting on **alpha-2 adrenergic receptors** on pancreatic beta cells. - This suppression is crucial for the stress response, as it allows **unopposed action of counter-regulatory hormones** to mobilize glucose and raise blood glucose levels. - The body prioritizes **immediate energy availability** (high blood glucose) over storage, making insulin the hormone that is **decreased, not increased**, during acute stress. *Growth hormone* - **Growth hormone** is a counter-regulatory hormone that **increases during acute stress** to mobilize energy stores, particularly by promoting lipolysis and gluconeogenesis. - Its actions contribute to the stress-induced elevation of **blood glucose levels**. *Epinephrine* - **Epinephrine** (adrenaline) is a primary catecholamine released during acute stress, leading to a rapid **fight or flight response**. - It significantly **increases heart rate**, blood pressure, and **glucose mobilization** through glycogenolysis and gluconeogenesis. *Glucagon* - **Glucagon** is a key hormone involved in **maintaining glucose homeostasis** and is significantly **increased during acute stress**. - It primarily acts on the liver to **stimulate glycogenolysis** and **gluconeogenesis**, thereby raising blood glucose levels to provide energy.

Q: Melatonin is secreted by

Pineal gland. ***Pineal gland*** - The **pineal gland** is a small endocrine gland located in the brain that primarily produces **melatonin**. - Its main function is to regulate **sleep-wake cycles** (circadian rhythms), with melatonin secretion increasing in darkness. *Melanocytes* - **Melanocytes** are cells found in the skin and eyes that produce **melanin**, a pigment responsible for skin, hair, and eye color. - They are not involved in the production of melatonin. *Hypothalamus* - The **hypothalamus** is a crucial part of the brain that links the nervous system to the endocrine system via the pituitary gland. - It produces various **releasing and inhibiting hormones** that control other glands, but it does not secrete melatonin. *Adrenal cortex* - The **adrenal cortex** is the outer part of the adrenal gland, responsible for producing **steroid hormones** like glucocorticoids (e.g., cortisol) and mineralocorticoids (e.g., aldosterone). - It does not produce melatonin; melatonin production is distinctly associated with the pineal gland.

Q: All are true for oxytocin EXCEPT:

Secreted by anterior pituitary. ***Secreted by anterior pituitary*** - Oxytocin is synthesized in the **hypothalamus** (specifically the paraventricular and supraoptic nuclei) and then transported down axons to the **posterior pituitary gland**, where it is stored and released. - The **anterior pituitary** produces and secretes hormones like growth hormone, prolactin, TSH, ACTH, FSH, and LH, but not oxytocin or vasopressin. *Causes ejection of milk* - Oxytocin acts on **myoepithelial cells** surrounding the alveoli of the mammary glands, causing them to contract and eject milk during lactation. - This is known as the **milk ejection reflex** or "let-down" reflex, which is stimulated by suckling. *Polypeptide* - Oxytocin is a **peptide hormone** composed of nine amino acids, making it a small polypeptide. - Its specific amino acid sequence is **Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2**, with a disulfide bond between the cysteine residues. *Secreted in both sexes* - While most recognized for its roles in childbirth and lactation in females, oxytocin is also produced and secreted in **males**. - In males, it is involved in various functions including **sperm transport**, sexual arousal, ejaculation, and social bonding behaviors.

Q: Which of the following causes hypocalcemia:

Calcitonin. ***Calcitonin*** - **Calcitonin** is a hormone secreted by the **parafollicular cells (C cells)** of the thyroid gland. - It **lowers serum calcium levels** by **inhibiting osteoclast activity** (preventing bone resorption) and **increasing renal calcium excretion**. - This is the only hormone among the options that causes hypocalcemia. *1,25-dihydroxycholecalciferol* - This is the **active form of vitamin D** (calcitriol), which **increases serum calcium levels**. - It promotes intestinal calcium absorption, enhances bone resorption, and increases renal calcium reabsorption. - Deficiency of this hormone leads to hypocalcemia, but the hormone itself raises calcium. *Parathormone* - **Parathyroid hormone (PTH)** is the primary regulator that **increases serum calcium levels**. - It stimulates **osteoclast activity** (releasing calcium from bone), increases renal calcium reabsorption, and promotes synthesis of 1,25-dihydroxycholecalciferol. - PTH acts opposite to calcitonin in calcium homeostasis. *Thyroid hormones* - **Thyroxine (T4) and triiodothyronine (T3)** primarily regulate metabolism and have **no direct role in calcium homeostasis**. - While severe thyroid dysfunction can indirectly affect bone turnover, thyroid hormones do not directly cause hypocalcemia.

Q: Neuroendocrine glands means:

Substance is released into the blood from the nerve. ***Substance is released into the blood from the nerve*** - Neuroendocrine glands are specialized neurons that synthesize and release **hormones** directly into the bloodstream, integrating the nervous and endocrine systems. - This **neurosecretion** allows neurons to exert widespread, long-lasting effects on target cells throughout the body. *Those acting at peripheral nervous system* - This describes the general function of peripheral nerves, which can be **motor**, **sensory**, or **autonomic**, but doesn't specifically define a neuroendocrine gland. - Neuroendocrine cells are typically found within the central and peripheral nervous systems but their defining characteristic is release into the **blood**, not just acting within the PNS. *Chemical acting at the synapse* - This describes a **neurotransmitter**, which is released from a neuron and acts locally on a postsynaptic neuron or effector cell across a synaptic cleft. - Unlike hormones, neurotransmitters exert their effects over very **short distances** and typically have a rapid, short-lived action. *Substance act on the cells that release it.* - This describes **autocrine signaling**, where a cell produces and secretes an extracellular mediator that binds to its own surface receptors. - While some neuroendocrine cells may exhibit autocrine regulation, their primary definition involves releasing substances into the **bloodstream** to act on distant targets, not solely on themselves.

Q: A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?

Acetylcholine. ***Acetylcholine*** - **Acetylcholine** is the primary neurotransmitter released by **preganglionic sympathetic fibers** that innervate the adrenal medulla. - Upon binding to **nicotinic receptors** on chromaffin cells, acetylcholine stimulates the release of catecholamines, including norepinephrine and epinephrine, into the bloodstream. *Normetanephrine* - **Normetanephrine** is a metabolite of **norepinephrine**, not a hormone that triggers its release. - It is formed by the action of **catechol-O-methyltransferase (COMT)** on norepinephrine. *Metanephrine* - **Metanephrine** is a metabolite of **epinephrine**, not a substance that stimulates catecholamine release from the adrenal medulla. - Like normetanephrine, it is also formed by the action of **COMT**. *Epinephrine* - **Epinephrine** (adrenaline) is a hormone primarily produced and released by the **adrenal medulla**, alongside norepinephrine. - While both are catecholamines, epinephrine does not trigger its own release or the release of norepinephrine in this context; instead, their release is stimulated by acetylcholine.

Q: Which of the following can cause an increase in growth hormone levels in blood?

Hypoglycemia. ***Hypoglycemia*** - **Hypoglycemia** is a potent stimulus for **growth hormone (GH) secretion**, as GH acts to raise blood glucose levels, serving as a counter-regulatory hormone. - The body perceives low blood glucose as a stressor, activating the **hypothalamic-pituitary-adrenal axis** and stimulating GH release to mobilize energy stores. *Cortisol* - **Cortisol** (a glucocorticoid) generally has an **inhibitory effect** on GH secretion at the hypothalamic and pituitary levels. - High levels of cortisol can lead to **suppression of GH pulsatility** and overall lower GH release. *Glucose* - An increase in **blood glucose** levels typically **suppresses growth hormone (GH) release**, as GH tends to increase blood glucose. - This negative feedback mechanism helps maintain **glucose homeostasis** within the body. *Methylprednisolone* - **Methylprednisolone** is a synthetic **glucocorticoid** that mimics the actions of cortisol. - Like cortisol, it suppresses GH secretion and can lead to **growth retardation** in children with chronic use.

Question 1

Leptin is secreted by?

Accepted Answer

Adipose tissue

Answer

Ovaries

Answer

Hypothalamus

Answer

Liver

Question 2

Which one is an example of short loop negative feedback mechanism?

Accepted Answer

TSH inhibiting TRH release from hypothalamus

Answer

TRH inhibiting its release from hypothalamus

Answer

T3, T4 inhibiting TRH release from hypothalamus

Answer

T3, T4 inhibiting TSH release from anterior pituitary

Question 3

What is the characteristic hormone pattern in hypergonadotropic hypogonadism?

Accepted Answer

Increase FSH increase LH

Answer

Decrease FSH and increase LH

Answer

Decrease FSH and LH

Answer

Increase FSH decrease LH

Question 4

All of the following are increased in Acute stress except

Accepted Answer

Insulin

Answer

Growth hormone

Answer

Epinephrine

Answer

Glucagon

Question 5

Melatonin is secreted by

Accepted Answer

Pineal gland

Answer

Melanocytes

Answer

Hypothalamus

Answer

Adrenal cortex

Question 6

All are true for oxytocin EXCEPT:

Accepted Answer

Secreted by anterior pituitary

Answer

Causes ejection of milk

Answer

Polypeptide

Answer

Secreted in both sexes

Question 7

Which of the following causes hypocalcemia:

Accepted Answer

Calcitonin

Answer

1, 25-dihydroxycholecalciferol

Answer

Parathormone

Answer

Thyroid hormones

Question 8

Neuroendocrine glands means:

Accepted Answer

Substance is released into the blood from the nerve

Answer

Those acting at peripheral nervous system

Answer

Chemical acting at the synapse

Answer

Substance acts on the cells that release it.

Question 9

A patient with a pheochromocytoma is secreting large amounts of norepinephrine into the bloodstream. In a normal individual, this compound is usually released from the adrenal medulla in response to which of the following?

Accepted Answer

Acetylcholine

Answer

Normetanephrine

Answer

Metanephrine

Answer

Epinephrine

Question 10

Which of the following can cause an increase in growth hormone levels in blood?

Accepted Answer

Hypoglycemia

Answer

Cortisol

Answer

Glucose

Answer

Methylprednisolone

Endocrinology — MCQs

Endocrinology — MCQs

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