Endocrinology Practice Questions

Q: Increased prolactin is associated with which of the following?

Increased estradiol. **Explanation:** The correct answer is **D. Increased estradiol**. This question tests the physiological feedback loops of the hypothalamic-pituitary-gonadal (HPG) axis. **Why D is correct:** Prolactin has a direct inhibitory effect on the hypothalamus. High levels of prolactin (hyperprolactinemia) suppress the pulsatile secretion of **Gonadotropin-Releasing Hormone (GnRH)**. Since GnRH is required to stimulate the anterior pituitary to release FSH and LH, a decrease in GnRH leads to low levels of these gonadotropins. Consequently, the ovaries (in females) or testes (in males) are not stimulated, leading to **decreased** production of sex steroids like **estradiol** and testosterone. Therefore, increased prolactin is associated with a *hypogonadotropic hypogonadal* state. **Why the other options are incorrect:** * **A. Increased FSH:** Prolactin inhibits GnRH, which leads to a **decrease** in FSH and LH levels. * **B. Increased libido:** Low levels of sex steroids (estradiol/testosterone) caused by hyperprolactinemia lead to **decreased** libido and sexual dysfunction. * **C. Increased testosterone:** As mentioned, the suppression of LH (due to low GnRH) results in **decreased** testosterone production in males. **High-Yield Clinical Pearls for NEET-PG:** * **Dopamine is the primary Prolactin-Inhibiting Factor (PIF).** Any drug that blocks dopamine (e.g., antipsychotics like Haloperidol or Metoclopramide) will cause hyperprolactinemia. * **TRH stimulates Prolactin:** In primary hypothyroidism, high TRH levels can lead to hyperprolactinemia. * **Clinical Triad in Females:** Amenorrhea, galactorrhea, and infertility. * **Clinical Presentation in Males:** Gynecomastia, erectile dysfunction, and decreased facial hair.

Q: Which of the following is NOT true about thyroxine?

Decreases the rate of respiration. **Explanation:** Thyroxine ($T_4$) and Triiodothyronine ($T_3$) are the primary determinants of the body’s metabolic pace. The correct answer is **C** because thyroid hormones **increase** the rate and depth of respiration, rather than decreasing it. **1. Why Option C is the correct choice (The "Not True" statement):** Thyroid hormones increase the Basal Metabolic Rate (BMR), leading to higher $O_2$ utilization and increased $CO_2$ production in tissues. To meet this demand and expel excess $CO_2$, thyroxine acts on the respiratory center to increase the **minute ventilation** (rate × tidal volume). Therefore, a decrease in respiration is physiologically inconsistent with hyperthyroidism. **2. Why the other options are incorrect (They are true statements):** * **Option A (Increases BMR):** This is the hallmark of thyroid action. It increases the activity of $Na^+-K^+$ ATPase pumps in almost all tissues, leading to increased energy expenditure and heat production (thermogenesis). * **Option B (Increases Oxygen Consumption):** As BMR rises, mitochondria consume more oxygen to produce ATP. This effect is seen in all tissues except the brain, anterior pituitary, and testes. * **Option D (Causes Lipolysis):** Thyroxine stimulates lipid metabolism. It activates hormone-sensitive lipase, leading to the breakdown of triglycerides into free fatty acids and glycerol to provide fuel for the increased metabolic rate. **Clinical Pearls for NEET-PG:** * **Cardiac Effects:** Thyroxine increases the expression of $\beta_1$ receptors, leading to tachycardia and increased cardiac output. * **Cholesterol:** Thyroid hormones increase the expression of LDL receptors in the liver; hence, **hypothyroidism** is a common cause of **hypercholesterolemia**. * **Growth:** Thyroid hormone is essential for bone maturation and CNS development (cretinism occurs if deficient in infancy).

Q: Which hormones are produced by the zona glomerulosa of the adrenal cortex?

Mineralocorticoids. **Explanation:** The adrenal gland is divided into an outer cortex and an inner medulla. The adrenal cortex is further organized into three distinct histological layers, each responsible for secreting specific steroid hormones. A popular mnemonic to remember these layers from superficial to deep is **GFR** (**G**lomerulosa, **F**asciculata, **R**eticularis). 1. **Zona Glomerulosa (Outer layer):** This layer produces **Mineralocorticoids**, primarily **Aldosterone**. These hormones are essential for regulating sodium and potassium balance and blood pressure via the Renin-Angiotensin-Aldosterone System (RAAS). 2. **Zona Fasciculata (Middle layer):** This is the widest layer and produces **Glucocorticoids**, mainly **Cortisol**, which regulates glucose metabolism and the stress response. 3. **Zona Reticularis (Inner layer):** This layer produces **Androgens** (sex steroids), such as Dehydroepiandrosterone (DHEA). **Analysis of Incorrect Options:** * **A. Catecholamines:** These (Epinephrine and Norepinephrine) are produced by the **Adrenal Medulla**, not the cortex. * **C. Glucocorticoids:** Produced by the Zona **Fasciculata**. * **D. Androgens:** Produced by the Zona **Reticularis**. **High-Yield NEET-PG Pearls:** * **Mnemonic:** **G**o **F**ind **R**ex, **S**alt **S**ugar **S**ex (Glomerulosa-Salt/Aldosterone; Fasciculata-Sugar/Cortisol; Reticularis-Sex/Androgens). * **Regulation:** The Zona Glomerulosa is primarily regulated by **Angiotensin II and Potassium levels**, whereas the Fasciculata and Reticularis are regulated by **ACTH**. * **Enzyme Deficiency:** In the most common form of Congenital Adrenal Hyperplasia (21-Hydroxylase deficiency), there is a failure to produce mineralocorticoids and glucocorticoids, leading to an overproduction of androgens.

Q: The provided diagram shows the adrenal gland. Identify the hormone produced from the area labeled 'A'.

Aldosterone. ***Aldosterone*** - Area 'A' represents the **zona glomerulosa**, the outermost layer of the adrenal cortex, which specifically produces **aldosterone**. - **Aldosterone** is a **mineralocorticoid** that regulates **sodium** and **potassium** balance and **blood pressure**. *Cortisol* - **Cortisol** is produced by the **zona fasciculata**, the middle layer of the adrenal cortex, not area 'A'. - This **glucocorticoid** primarily regulates **glucose metabolism** and **stress response**. *Epinephrine* - **Epinephrine** (adrenaline) is produced by the **adrenal medulla**, the innermost part of the adrenal gland. - This **catecholamine** is involved in the **fight-or-flight response** and **sympathetic nervous system** activation. *Androgen* - **Androgens** (like **DHEA**) are produced by the **zona reticularis**, the innermost cortical layer. - These **sex hormones** are precursors to **testosterone** and **estrogen**, not produced in area 'A'.

Q: Which of the following is both synthesized and stored in the hypothalamus?

Somatostatin. **Explanation:** The correct answer is **Somatostatin**. To answer this question correctly, one must distinguish between hormones that are merely produced in the hypothalamus and those that are both produced and stored there. **1. Why Somatostatin is Correct:** Somatostatin (Growth Hormone Inhibiting Hormone) is a regulatory hormone **synthesized** in the periventricular nucleus of the hypothalamus. It is **stored** in the median eminence (the inferior-most portion of the hypothalamus) before being released into the hypophyseal portal system to inhibit the secretion of Growth Hormone and TSH from the anterior pituitary. **2. Why the other options are incorrect:** * **ADH (Antidiuretic Hormone):** While ADH is **synthesized** in the hypothalamus (supraoptic and paraventricular nuclei), it is **stored** and released from the **posterior pituitary** (neurohypophysis). * **TSH and LH:** These are trophic hormones **synthesized and stored** in the **anterior pituitary** (adenohypophysis) by thyrotropes and gonadotropes, respectively. Their release is controlled by hypothalamic "releasing hormones" (TRH and GnRH). **Clinical Pearls for NEET-PG:** * **The "Two-Site" Rule:** Remember that ADH and Oxytocin are hypothalamic hormones by origin but **pituitary hormones by storage**. * **Somatostatin Locations:** It is found in three main areas: the Hypothalamus (inhibits GH), Delta cells of the Pancreas (inhibits insulin/glucagon), and D cells of the GI tract (inhibits gastrin). * **Octreotide:** A high-yield synthetic analog of somatostatin used clinically to treat acromegaly, carcinoid syndrome, and esophageal varices.

Q: Obesity is ordinarily associated with low ghrelin levels. Which of the following conditions is an exception where obesity is associated with high ghrelin levels?

Prader-Willi syndrome. ### Explanation **Core Concept: The Ghrelin Paradox** Ghrelin is an orexigenic (appetite-stimulating) hormone secreted primarily by the P-cells of the gastric fundus. In normal physiology, ghrelin levels follow an inverse relationship with Body Mass Index (BMI). In common obesity, ghrelin levels are **low** because the body attempts to suppress further food intake in response to positive energy balance. **Why Prader-Willi Syndrome (PWS) is the Exception:** Prader-Willi Syndrome is a genetic disorder (deletion of the paternal 15q11-q13 locus) characterized by hyperphagia and early-onset morbid obesity. Unlike common obesity, PWS is uniquely associated with **markedly elevated fasting ghrelin levels**. This hyperghrelinemia is believed to drive the insatiable hunger and lack of satiety characteristic of the syndrome, making it a classic "exception to the rule" in endocrinology. **Analysis of Incorrect Options:** * **A. Hypothyroidism:** Associated with weight gain due to a low metabolic rate, but ghrelin levels are typically normal or decreased, following the standard inverse relationship with BMI. * **C. Hypoadrenalism (Addison’s Disease):** Usually presents with weight loss and anorexia, not obesity. * **D. Insulinoma:** Causes hypoglycemia leading to increased appetite and weight gain. However, the hyperinsulinemia typically suppresses ghrelin levels. **High-Yield Clinical Pearls for NEET-PG:** * **Ghrelin vs. Leptin:** Ghrelin is the "Hunger Hormone" (levels rise before meals); Leptin is the "Satiety Hormone" (secreted by adipocytes). * **Sleep Deprivation:** Associated with increased ghrelin and decreased leptin, contributing to obesity. * **Post-Gastric Bypass:** Ghrelin levels significantly **decrease** after Roux-en-Y gastric bypass, which contributes to the surgery's success in weight loss. * **PWS Triad:** Hypotonia (infancy), Hyperphagia/Obesity, and Hypogonadism.

Q: All of the following are true about neuropeptide Y EXCEPT:

It decreases food intake.. **Explanation:** Neuropeptide Y (NPY) is a 36-amino acid peptide widely distributed in the central and peripheral nervous systems. It is one of the most potent **orexigenic** (appetite-stimulating) peptides known. **Why Option D is the Correct Answer (The Exception):** NPY **increases** food intake; it does not decrease it. It is synthesized in the arcuate nucleus of the hypothalamus and acts on the paraventricular nucleus to stimulate hunger and promote weight gain. Substances that decrease food intake are called anorexigenic (e.g., Leptin, POMC, and CART). **Analysis of Other Options:** * **Option A:** NPY is indeed a polypeptide consisting of **36 amino acids**. It belongs to the same family as Peptide YY (PYY) and Pancreatic Polypeptide (PP). * **Option B:** While NPY is a potent vasoconstrictor in many vascular beds, it is known to cause **vasodilation** in specific tissues (like the heart and brain) under certain physiological conditions, often through the release of nitric oxide or by modulating sympathetic tone. (Note: In many textbooks, it is primarily highlighted as a co-transmitter with norepinephrine causing vasoconstriction, but its multifaceted role includes complex vascular regulation). * **Option C:** NPY acts as a **neurotransmitter** and neuromodulator. It is often co-stored and co-released with Norepinephrine in postganglionic sympathetic neurons. **High-Yield Clinical Pearls for NEET-PG:** * **Hypothalamic Control:** NPY/AgRP neurons are inhibited by **Leptin** and **Insulin** (satiety signals) and stimulated by **Ghrelin** (the hunger hormone). * **Location:** Highest concentrations are found in the **Arcuate Nucleus** of the Hypothalamus. * **Functions:** Beyond appetite, NPY is involved in regulating circadian rhythms, reducing anxiety (anxiolytic), and modulating cardiovascular function.

Q: Which of the following hormones is not secreted by the kidney?

Angiotensin I. **Explanation:** The kidney functions as both an excretory and an endocrine organ. The correct answer is **Angiotensin I** because it is not secreted by the kidney; rather, it is **produced in the circulating blood.** 1. **Why Angiotensin I is the correct answer:** The kidney secretes the enzyme **Renin**. Renin acts on **Angiotensinogen** (a plasma protein synthesized by the liver) to cleave it into **Angiotensin I**. Therefore, Angiotensin I is a product of an enzymatic reaction occurring in the plasma, not a direct secretion from renal cells. 2. **Analysis of incorrect options:** * **Renin:** Secreted by the **Juxtaglomerular (JG) cells** of the afferent arteriole in response to low blood pressure or low chloride delivery to the macula densa. * **Erythropoietin (EPO):** Produced by **interstitial cells (peritubular capillaries)** in the renal cortex. it stimulates RBC production in the bone marrow in response to hypoxia. * **1, 25-dihydroxycholecalciferol (Calcitriol):** The kidney contains the enzyme **1-alpha-hydroxylase** (in the proximal convoluted tubule), which converts inactive 25-hydroxyvitamin D into the active form, Calcitriol. **High-Yield NEET-PG Pearls:** * **Site of ACE:** Angiotensin I is converted to Angiotensin II primarily in the **lungs** by Angiotensin-Converting Enzyme (ACE) located on the vascular endothelium. * **Thrombopoietin:** While primarily produced in the liver, a small amount is also synthesized in the kidney. * **Prostaglandins:** The kidney also produces PGE2 and PGI2 (vasodilators) which help maintain renal blood flow.

Q: Which of the following hormones increases during sleep?

GH. **Explanation:** The correct answer is **GH (Growth Hormone)**. Growth hormone secretion follows a distinct pulsatile and circadian rhythm, with its most significant peak occurring during sleep. **1. Why GH is correct:** GH secretion is maximal during **Slow-Wave Sleep (Stage N3/Deep Sleep)**, typically occurring within the first 90 minutes after sleep onset. This surge is mediated by an increase in GHRH (Growth Hormone Releasing Hormone) and a decrease in Somatostatin. In children and adolescents, this sleep-associated peak is crucial for linear growth and metabolic repair. **2. Why other options are incorrect:** * **ACTH and Glucocorticoids (Cortisol):** These follow a diurnal rhythm but are at their **lowest** levels during the early part of the night (around midnight). Their levels begin to rise in the early morning hours (3 AM – 4 AM) and peak just before awakening (the "dawn phenomenon"). * **Insulin:** Insulin levels are primarily regulated by blood glucose levels (post-prandial). During sleep (a fasting state), insulin levels generally decrease to allow for glucagon-mediated glycogenolysis and gluconeogenesis to maintain basal glucose levels. **High-Yield Clinical Pearls for NEET-PG:** * **Sleep Stages:** GH peaks specifically during **Stage 3 (N3) NREM sleep**. If sleep is deprived or fragmented, GH secretion is significantly blunted. * **Other Hormones that increase during sleep:** Prolactin, Melatonin, and TSH (TSH peaks just before sleep onset). * **Somatomedins:** While GH is pulsatile, IGF-1 (Somatomedin C) levels remain stable throughout the day and are used for the clinical screening of Acromegaly. * **Inhibitors of GH:** Hyperglycemia, Free Fatty Acids, and Somatostatin.

Question 1

Reduction in estradiol levels leads to all except?

Accepted Answer

Increase in α2 receptor concentration.

Answer

Increase in hypothalamic Norepinephrine.

Answer

Increase in hypothalamic serotonin.

Answer

Decrease in α2 receptor concentration.

Question 2

Increased prolactin is associated with which of the following?

Accepted Answer

Increased estradiol

Answer

Increased FSH

Answer

Increased libido

Answer

Increased testosterone

Question 3

Which of the following is NOT true about thyroxine?

Accepted Answer

Decreases the rate of respiration

Answer

Increases basal metabolic rate (BMR)

Answer

Increases oxygen consumption

Answer

Causes lipolysis

Question 4

Which hormones are produced by the zona glomerulosa of the adrenal cortex?

Accepted Answer

Mineralocorticoids

Answer

Catecholamines

Answer

Glucocorticoids

Answer

Androgens

Question 5

The provided diagram shows the adrenal gland. Identify the hormone produced from the area labeled 'A'.

Accepted Answer

Aldosterone

Answer

Cortisol

Answer

Epinephrine

Answer

Androgen

Question 6

Which of the following is both synthesized and stored in the hypothalamus?

Accepted Answer

Somatostatin

Answer

ADH

Answer

Thyroid-stimulating hormone (TSH)

Answer

LH

Question 7

Obesity is ordinarily associated with low ghrelin levels. Which of the following conditions is an exception where obesity is associated with high ghrelin levels?

Accepted Answer

Prader-Willi syndrome

Answer

Hypothyroidism

Answer

Hypoadrenalism

Answer

Insulinoma

Question 8

All of the following are true about neuropeptide Y EXCEPT:

Accepted Answer

It decreases food intake.

Answer

It consists of 36 amino acids.

Answer

It causes vasodilatation.

Answer

It acts as a neurotransmitter.

Question 9

Which of the following hormones is not secreted by the kidney?

Accepted Answer

Angiotensin I

Answer

Renin

Answer

Erythropoietin

Answer

1, 25-dihydroxycholecalciferol

Question 10

Which of the following hormones increases during sleep?

Accepted Answer

GH

Answer

Insulin

Answer

ACTH

Answer

Glucocorticoid

Endocrinology — MCQs

Endocrinology — MCQs

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