Hypothalamus and Pituitary Gland — MCQs
Most common tumour of the pituitary is -
Which of the following inhibit gonadotropin-releasing hormone pulse secretion?
Most common cause of Cushing's syndrome is what?
Hypothalamus increases release of all hormones from the pituitary except ?
All of the following are known functions of hypothalamus except
Intracranial Irradiation most commonly leads to deficiency of
Which hormone has permissive role in puberty?
Secretion of prolactin is inhibited by?
In the puerperium, which of the following hormonal changes are responsible for lactogenesis? 1. A sudden fall in the oestrogen levels after delivery 2. Reduction of prolactin inhibiting factor from the hypothalamus 3. Release of prolactin from the anterior pituitary 4. Release of oxytocin from the posterior pituitary Select the correct answer using the code given below :
Which of the following inhibits appetite by counteracting the effects of neuropeptide Y?
Hypothalamus and Pituitary Gland Indian Medical PG Practice Questions and MCQs
Question 1: Most common tumour of the pituitary is -
- A. ACTH secreting adenoma
- B. Prolactinoma (Correct Answer)
- C. TSH secreting adenoma
- D. GH secreting adenoma
Explanation: ***Prolactinoma*** - **Prolactinomas** are the most frequently occurring type of pituitary adenoma, accounting for approximately **40-50%** of all pituitary tumors [1]. - They are characterized by the **overproduction of prolactin**, leading to symptoms like **galactorrhea**, **amenorrhea**, and **infertility** [1]. *ACTH secreting adenoma* - This type of adenoma leads to **Cushing's disease** due to excessive **ACTH production**, stimulating adrenal cortisol synthesis [2]. - While significant, **ACTH-secreting adenomas** are less common than prolactinomas, accounting for about **15-20%** of pituitary tumors. *TSH secreting adenoma* - **TSH-secreting adenomas** are extremely rare, making up less than **1%** of all pituitary tumors. - They cause secondary hyperthyroidism due to excessive **thyroid-stimulating hormone (TSH)** secretion. *GH secreting adenoma* - **Growth hormone (GH) secreting adenomas** cause **acromegaly** in adults and **gigantism** in children [1]. - These tumors are less common than prolactinomas, constituting about **15-20%** of pituitary adenomas.
Question 2: Which of the following inhibit gonadotropin-releasing hormone pulse secretion?
- A. Prolactin (Correct Answer)
- B. Oxytocin
- C. Thyroxine
- D. Insulin
Explanation: ***Prolactin*** - Elevated levels of **prolactin** inhibit the pulsatile secretion of **gonadotropin-releasing hormone (GnRH)** from the hypothalamus. - This inhibition leads to decreased production of **luteinizing hormone (LH)** and **follicle-stimulating hormone (FSH)** from the pituitary, ultimately affecting gonadal function. *Thyroxine* - **Thyroxine** (thyroid hormone) primarily regulates metabolism and growth, and while it interacts with the reproductive axis, its direct effect is not typically the **inhibition of GnRH pulse secretion**. - Extreme thyroid dysfunction can indirectly impact reproductive hormones, but it's not the primary mechanism of GnRH inhibition. *Oxytocin* - **Oxytocin** is largely involved in **uterine contractions** during labor and **milk ejection** during lactation, and has roles in social bonding. - It does not directly inhibit the pulsatile release of **GnRH**. *Insulin* - **Insulin** is a key hormone in **glucose metabolism** and energy regulation. - While insulin resistance and hyperinsulinemia can affect reproductive function (e.g., in polycystic ovary syndrome, PCOS), it does not **directly inhibit GnRH pulse secretion**.
Question 3: Most common cause of Cushing's syndrome is what?
- A. Adrenal adenoma
- B. Adrenal carcinoma
- C. McCune Albright syndrome
- D. Pituitary adenoma (Correct Answer)
Explanation: ***Pituitary adenoma*** - The **most common cause** of Cushing's syndrome, specifically **Cushing's disease**, is excess ACTH production from a pituitary adenoma [1]. - This leads to **overstimulation of the adrenal glands**, resulting in increased cortisol production [1]. *McCune Albright syndrome* - It is a genetic disorder characterized by **fibrous dysplasia**, **café-au-lait spots**, and **endocrine problems**, not primarily Cushing's syndrome. - Though hormone abnormalities may present, it is not the **most common** cause of Cushing's syndrome. *Adrenal carcinoma* - While adrenal carcinoma can cause **Cushing's syndrome**, it is less common compared to the **pituitary adenoma** [1]. - This malignant tumor is rare and typically presents with more aggressive features and higher cortisol levels. *Adrenal adenoma* - Adrenal adenomas are benign tumors that can produce **excess cortisol**, but they are not the leading cause of Cushing's syndrome overall [1]. - They account for a smaller proportion of cases compared to **pituitary adenomas**.
Question 4: Hypothalamus increases release of all hormones from the pituitary except ?
- A. ACTH
- B. TSH
- C. FSH
- D. Prolactin (Correct Answer)
Explanation: ***Prolactin*** - The hypothalamus primarily **inhibits prolactin release** from the anterior pituitary via **dopamine** (prolactin-inhibiting hormone). - All other hormones listed (ACTH, TSH, FSH/LH, GH) are stimulated by their respective hypothalamic releasing hormones. *ACTH* - The hypothalamus **increases ACTH release** by secreting **corticotropin-releasing hormone (CRH)**, which acts on the anterior pituitary. - CRH stimulates corticotrophs to synthesize and release ACTH, which then acts on the adrenal glands. *TSH* - The hypothalamus **increases TSH release** by secreting **thyrotropin-releasing hormone (TRH)**, which stimulates thyrotrophs in the anterior pituitary. - TRH also has a minor stimulatory effect on prolactin release, but its primary role is TSH stimulation. *FSH* - The hypothalamus **increases FSH release** (along with LH) by secreting **gonadotropin-releasing hormone (GnRH)** in a pulsatile manner. - GnRH stimulates gonadotrophs in the anterior pituitary to produce and secrete both FSH and LH.
Question 5: All of the following are known functions of hypothalamus except
- A. Temperature regulation
- B. Hypophyseal control
- C. Food intake
- D. Increase in heart rate with exercise (Correct Answer)
Explanation: ***Increase in heart rate with exercise*** - The **hypothalamus** has an indirect role in cardiovascular responses during exercise, primarily through its influence on the **autonomic nervous system** to maintain homeostasis. - However, the primary control of increased heart rate during exercise originates from the **medulla oblongata** and the **motor cortex**, which directly modulates the sympathetic nervous system to increase cardiac output. *Temperature regulation* - The **hypothalamus** contains thermoregulatory centers that monitor and adjust body temperature through mechanisms such as **sweating** and **shivering**. - This function is a fundamental aspect of maintaining **homeostasis**. *Hypophyseal control* - The **hypothalamus** directly controls the **pituitary gland** (hypophysis) by producing releasing and inhibiting hormones that regulate the secretion of pituitary hormones. - This neuroendocrine function is crucial for controlling various **endocrine axes**. *Food intake* - The **hypothalamus** plays a key role in regulating appetite and satiety, with specific nuclei like the **arcuate nucleus** integrating signals related to hunger and fullness. - This control is essential for maintaining **energy balance**.
Question 6: Intracranial Irradiation most commonly leads to deficiency of
- A. ACTH
- B. PROLACTIN
- C. GROWTH HORMONE (Correct Answer)
- D. TSH
Explanation: ***GROWTH HORMONE*** - **Growth hormone (GH)** deficiency is the most common endocrine complication following **intracranial irradiation**, particularly affecting children and adolescents due to the sensitivity of somatotrophs. - The somatotrophs, responsible for GH production, are highly vulnerable to radiation damage, often manifesting as GH deficiency even at lower radiation doses or earlier after treatment. *ACTH* - **ACTH deficiency** (leading to secondary adrenal insufficiency) can occur after intracranial irradiation but is less common and typically appears later or at higher radiation doses than GH deficiency. - The corticotrophs, which produce ACTH, are generally more resilient to radiation compared to somatotrophs. *PROLACTIN* - **Prolactin deficiency** is relatively rare following intracranial irradiation, as lactotrophs (prolactin-producing cells) are among the most radioresistant pituitary cells. - Conversely, hyperprolactinemia due to damage to the dopamine inhibitory pathways is more frequently observed than prolactin deficiency. *TSH* - **TSH deficiency** (central hypothyroidism) can occur after intracranial irradiation but is less common than GH deficiency and tends to manifest later. - Thyrotrophs, which produce TSH, are more radiosensitive than lactotrophs and corticotrophs but less so than somatotrophs.
Question 7: Which hormone has permissive role in puberty?
- A. GH
- B. Leptin (Correct Answer)
- C. GnRH
- D. Insulin
Explanation: ***Leptin*** - **Leptin** acts as a permissive signal that informs the hypothalamus about the body's **nutritional status** and energy reserves. - A certain threshold level of **leptin**, reflecting adequate body fat, is generally required for the initiation and progression of puberty. *GH* - **Growth hormone (GH)** is crucial for overall somatic growth during childhood and adolescence, but it does not directly trigger the onset of puberty. - While GH is important for the pubertal growth spurt, it acts primarily in an anabolic role rather than initiating the reproductive axis. *GnRH* - **Gonadotropin-releasing hormone (GnRH)** is the primary neurohormone that directly initiates and drives puberty by stimulating the pituitary. - However, GnRH is the *driver* of puberty rather than a *permissive* factor, meaning its pulsatile release is the direct trigger for the reproductive cascade. *Insulin* - **Insulin** is involved in glucose metabolism and energy homeostasis throughout the body. - While good metabolic health is indirectly important for puberty, insulin does not play a direct permissive role in initiating the pubertal process like leptin does.
Question 8: Secretion of prolactin is inhibited by?
- A. Dopamine (Correct Answer)
- B. Serotonin
- C. Noradrenaline
- D. Adrenaline
Explanation: ***Dopamine*** - **Dopamine**, produced by the **hypothalamus**, is the primary physiological inhibitor of **prolactin secretion** from the anterior pituitary gland. - It acts on **D2 receptors** on lactotrophs, leading to a decrease in prolactin synthesis and release. *Serotonin* - **Serotonin** generally has a stimulatory effect on **prolactin secretion**, rather than an inhibitory one. - Elevated serotonin levels can lead to **hyperprolactinemia**. *Noradrenaline* - While **noradrenaline** can have complex effects on pituitary hormones, it is not considered the primary direct inhibitor of **prolactin secretion**. - Its influence is often indirect or less potent than that of **dopamine**. *Adrenaline* - **Adrenaline** (epinephrine) is a neurotransmitter and hormone primarily involved in the **"fight or flight" response** and does not directly inhibit **prolactin secretion**. - Its effects on pituitary hormone release are typically less direct compared to **dopamine's** specific action on lactotrophs.
Question 9: In the puerperium, which of the following hormonal changes are responsible for lactogenesis? 1. A sudden fall in the oestrogen levels after delivery 2. Reduction of prolactin inhibiting factor from the hypothalamus 3. Release of prolactin from the anterior pituitary 4. Release of oxytocin from the posterior pituitary Select the correct answer using the code given below :
- A. 1, 2 and 3 (Correct Answer)
- B. 1 and 2 only
- C. 1 and 4
- D. 2, 3 and 4
Explanation: ***1, 2 and 3*** - **Lactogenesis** (milk production) critically depends on the **sudden drop in estrogen** after delivery, which removes the inhibitory effect on prolactin. - This, combined with the **release of prolactin from the anterior pituitary** (due to reduced **prolactin-inhibiting factor**, or dopamine, from the hypothalamus), stimulates the glandular cells in the breast to produce milk. *1 and 2 only* - This option correctly identifies the sudden fall in **estrogen** and reduction of **prolactin-inhibiting factor**'s influence but omits the direct action of **prolactin** release from the anterior pituitary, which is essential for milk synthesis. - While estrogen decline and reduced PIF are crucial, they lead to the **release of prolactin**, which is the direct stimulus for lactogenesis. *1 and 4* - While the sudden fall in **estrogen** is critical for initiating lactogenesis, **oxytocin** (released from the posterior pituitary) is primarily responsible for **milk ejection (let-down)**, not milk production (lactogenesis). - Oxytocin acts on myoepithelial cells to contract and expel milk, whereas prolactin stimulates milk synthesis. *2, 3 and 4* - This option correctly identifies the reduction of **prolactin-inhibiting factor** and the release of **prolactin**, which are essential for lactogenesis. However, it incorrectly includes **oxytocin**, which is involved in milk ejection, and misses the crucial role of the **fall in estrogen levels** that permits prolactin to act. - The elevated **estrogen levels during pregnancy** inhibit the action of prolactin, so their drop is a prerequisite for effective milk production.
Question 10: Which of the following inhibits appetite by counteracting the effects of neuropeptide Y?
- A. Orexins
- B. Leptin (Correct Answer)
- C. Neuropeptide Y
- D. Ghrelin
Explanation: ***Leptin*** - **Leptin** is a hormone primarily produced by **adipose tissue** that signals satiety to the brain, effectively counteracting the appetite-stimulating effects of neuropeptide Y. - It acts on receptors in the **hypothalamus** to reduce food intake and increase energy expenditure, thereby inhibiting appetite. *Orexins* - **Orexins** (also known as hypocretins) are **neurotransmitters** involved in regulating **wakefulness** and appetite. - Their primary role related to appetite is typically to **stimulate hunger** and food seeking behavior, rather than inhibiting it. *Neuropeptide Y* - **Neuropeptide Y (NPY)** is a potent **orexigenic peptide**, meaning it **stimulates appetite** and food intake. - It promotes the consumption of carbohydrates and is a key mediator of hunger signals in the brain through its action on the **hypothalamus**. *Ghrelin* - **Ghrelin** is a hormone produced mainly in the **stomach** that acts as a strong **appetite stimulant**. - It is often referred to as the "**hunger hormone**" and its levels rise before meals, signaling the brain to initiate food seeking.
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