Endocrinology Practice Questions

Q: Which of the following statements about the hormone leptin is FALSE?

Leptin stimulates appetite.. ### Explanation **Correct Answer: D. Leptin stimulates appetite.** **Why Option D is the correct (False) statement:** Leptin is an **anorexigenic** hormone, meaning it **suppresses appetite**. It is often referred to as the "satiety hormone." Leptin acts on the arcuate nucleus of the hypothalamus to inhibit Neuropeptide Y (NPY) and Agouti-related peptide (AgRP)—which are hunger stimulants—while simultaneously stimulating Pro-opiomelanocortin (POMC) neurons to promote satiety and increase energy expenditure. **Analysis of Incorrect Options:** * **Option A:** In most cases of human obesity, leptin levels are high. However, obese individuals often suffer from **leptin resistance**, where the brain fails to respond to the satiety signal despite high circulating levels. * **Option B:** The primary site of action for leptin is the **Hypothalamus** (specifically the arcuate nucleus), where it regulates long-term energy balance and body weight. * **Option C:** Leptin is a peptide hormone primarily synthesized and secreted by **white adipose tissue** (adipocytes). The amount of leptin secreted is directly proportional to the total body fat mass. **High-Yield NEET-PG Pearls:** * **Gene Association:** Leptin is encoded by the *ob* (obese) gene; its receptor is encoded by the *db* (diabetes) gene. * **Thermoregulation:** Leptin increases metabolic rate and heat production by stimulating sympathetic activity and upregulating **uncoupling protein-1 (UCP1/Thermogenin)** in brown adipose tissue. * **Opposing Hormone:** **Ghrelin**, produced by the stomach (P/D1 cells), is the "hunger hormone" and acts as the physiological antagonist to leptin. * **Reproduction:** Leptin is necessary for the onset of puberty; very low levels (as seen in anorexia or extreme exercise) can lead to hypothalamic amenorrhea.

Q: Which of the following inhibits the secretion of Growth Hormone (GH)?

Hyperglycemia. **Explanation:** Growth Hormone (GH) secretion is regulated by a complex interplay of hypothalamic factors and metabolic signals. **Why Hyperglycemia is Correct:** GH is a **diabetogenic hormone**; it increases blood glucose levels by stimulating gluconeogenesis and antagonizing insulin action. According to the negative feedback principle, **Hyperglycemia** (high blood glucose) inhibits GH secretion to prevent further glucose elevation. This occurs via the stimulation of hypothalamic **Somatostatin** (Growth Hormone Inhibiting Hormone - GHIH) and the direct inhibition of the anterior pituitary. **Why Other Options are Incorrect:** * **Bromocriptine:** In healthy individuals, dopamine agonists like Bromocriptine actually *stimulate* GH release. (Note: Paradoxically, it inhibits GH in patients with Acromegaly, which is a common clinical confusion). * **Vigorous Exercise:** Physical stress and exercise are potent physiological *stimulators* of GH secretion, mediated via increased sympathetic tone and GHRH release. * **Deep Sleep:** GH is secreted in pulsatile bursts, with the largest peak occurring during **Stage 3 and 4 (NREM) deep sleep**. Sleep deprivation significantly suppresses GH levels. **High-Yield NEET-PG Pearls:** 1. **Stimulators of GH:** Hypoglycemia (most potent metabolic stimulus), fasting/starvation, Ghrelin, Arginine (amino acids), and Sleep. 2. **Inhibitors of GH:** Hyperglycemia, Free Fatty Acids (FFA), Somatostatin, and IGF-1 (via negative feedback). 3. **Clinical Correlation:** The **Oral Glucose Tolerance Test (OGTT)** is the gold standard for diagnosing Acromegaly. In a healthy person, a glucose load suppresses GH to <1 ng/mL; failure to suppress confirms the diagnosis.

Q: Excessive secretion of ACTH causes which of the following conditions?

Cushing's syndrome. **Explanation:** **1. Why Cushing’s Syndrome is Correct:** Adrenocorticotropic hormone (ACTH), secreted by the anterior pituitary, stimulates the adrenal cortex to produce cortisol. Excessive secretion of ACTH (most commonly due to a pituitary adenoma, known specifically as **Cushing’s Disease**) leads to chronic hypercortisolism. This clinical state is characterized by the classic symptoms of **Cushing’s Syndrome**, including "moon facies," "buffalo hump," central obesity, purple striae, and hypertension. **2. Why Other Options are Incorrect:** * **Addison’s Disease:** This is primary adrenocortical insufficiency (low cortisol and aldosterone). In this condition, ACTH levels are actually **elevated** as a compensatory mechanism (negative feedback), but the primary pathology is the *lack* of adrenal response, not the *excess* of ACTH itself. * **Myxoedema:** This refers to severe **hypothyroidism** in adults, caused by a deficiency of thyroid hormones (T3/T4), not ACTH. * **Thyrotoxicosis:** This is a clinical state resulting from excessive circulating **thyroid hormones**, usually associated with Grave’s disease or toxic nodular goiter. **3. NEET-PG High-Yield Pearls:** * **Cushing’s Disease vs. Syndrome:** "Cushing’s Disease" specifically refers to a pituitary tumor secreting ACTH. "Cushing’s Syndrome" is the broad term for hypercortisolism from any cause (iatrogenic, adrenal tumor, or ectopic ACTH). * **Hyperpigmentation:** Excessive ACTH causes skin hyperpigmentation because ACTH is derived from **POMC (Pro-opiomelanocortin)**, which also produces Melanocyte-Stimulating Hormone (MSH). * **Dexamethasone Suppression Test (DST):** High-dose DST is used to differentiate Cushing’s Disease (suppresses) from ectopic ACTH production (does not suppress).

Q: A patient sustains a pituitary stalk transection due to an accident. Which of the following physiological responses will NOT occur?

Diabetes mellitus. **Explanation:** Pituitary stalk transection (infundibular injury) disrupts the connection between the hypothalamus and the pituitary gland. This results in the loss of hypothalamic releasing hormones and the interruption of the hypothalamic-hypophyseal portal system. **Why Diabetes Mellitus is the correct answer:** Diabetes Mellitus is a metabolic disorder characterized by hyperglycemia due to insulin deficiency or resistance. It is related to the **pancreas**, not the pituitary gland. In fact, pituitary stalk transection leads to a loss of Growth Hormone (GH) and ACTH (cortisol), both of which are "diabetogenic" (insulin-antagonistic) hormones. Therefore, stalk injury would more likely lead to **increased insulin sensitivity** or hypoglycemia, rather than Diabetes Mellitus. **Analysis of Incorrect Options:** * **Diabetes Insipidus (B):** The stalk contains the axons of the supraoptic and paraventricular nuclei. Transection prevents ADH (Vasopressin) from reaching the posterior pituitary for release, leading to central diabetes insipidus. * **Hyperprolactinemia (C):** Prolactin is the only anterior pituitary hormone under tonic **inhibition** by hypothalamic dopamine. Stalk transection removes this "dopamine brake," causing prolactin levels to rise. * **Hypothyroidism (D):** Transection prevents Hypothalamic TRH from reaching the anterior pituitary, leading to secondary hypothyroidism (low TSH and T4). **NEET-PG High-Yield Pearls:** 1. **The "Rule of Prolactin":** In any hypothalamic-pituitary destructive lesion, all anterior pituitary hormones decrease **except Prolactin**, which increases. 2. **Panhypopituitarism:** Stalk injury typically causes deficiency of GH, LH/FSH, TSH, and ACTH. 3. **Houssay Phenomenon:** This refers to the spontaneous improvement of hyperglycemia in a diabetic patient who subsequently develops pituitary insufficiency (due to loss of GH and Cortisol).

Q: Which one of the following makes epiphyseal cartilage matrix fail to calcify?

Hypovitaminosis D. **Explanation:** **Why Hypovitaminosis D is correct:** Vitamin D (Calcitriol) is essential for the mineralization of the bone matrix. Its primary role is to maintain adequate serum levels of Calcium and Phosphate by increasing intestinal absorption. In **Hypovitaminosis D**, there is a deficiency of these minerals in the extracellular fluid. Consequently, while the chondrocytes continue to proliferate and create the osteoid (organic matrix) at the epiphyseal plate, this matrix **fails to calcify**. This leads to the accumulation of unmineralized osteoid, resulting in the clinical condition known as **Rickets** in children and **Osteomalacia** in adults. **Why the other options are incorrect:** * **Thyroxine (A):** Thyroid hormones are essential for linear growth and skeletal maturation. Deficiency leads to delayed epiphyseal closure and stunting (Cretinism), but it does not specifically cause a failure of matrix calcification. * **Hypervitaminosis A (B):** Excessive Vitamin A accelerates the resorption of cartilage and bone, leading to premature closure of the epiphyses and thinning of the bone cortex, rather than a failure of calcification. * **Hydrocortisone (D):** Glucocorticoids generally inhibit bone formation by decreasing osteoblast activity and reducing intestinal calcium absorption, but they do not specifically target the calcification mechanism of the epiphyseal cartilage matrix in the same manner as Vitamin D deficiency. **High-Yield NEET-PG Pearls:** * **Rickets Hallmark:** Failure of osteoid mineralization + expansion of the epiphyseal plate (widening/cupping/fraying on X-ray). * **Vitamin D Pathway:** 7-dehydrocholesterol → Cholecalciferol (Skin) → 25-OH Vit D (Liver) → 1,25-(OH)₂ Vit D (Kidney via 1-alpha-hydroxylase). * **Alkaline Phosphatase (ALP):** Characteristically **elevated** in Vitamin D deficiency as osteoblasts attempt to compensate for the lack of mineralization.

Q: Hyperkalemia stimulates the secretion of which hormone?

Aldosterone. **Explanation:** **Aldosterone** is the primary mineralocorticoid secreted by the *zona glomerulosa* of the adrenal cortex. Its secretion is regulated by two main stimuli: the **Renin-Angiotensin-Aldosterone System (RAAS)** and **plasma potassium levels**. When plasma potassium levels rise (Hyperkalemia), it directly depolarizes the membranes of the zona glomerulosa cells. This opens voltage-gated calcium channels, leading to an influx of calcium, which triggers the synthesis and release of aldosterone. Once secreted, aldosterone acts on the **principal cells** of the late distal tubule and collecting duct to increase the activity of Na⁺/K⁺-ATPase pumps and ENaC channels. This results in sodium reabsorption and, crucially, **increased potassium secretion** into the urine, thereby restoring potassium homeostasis. **Why other options are incorrect:** * **Antidiuretic hormone (ADH):** Primarily regulated by plasma osmolarity and blood volume; its main role is water reabsorption via aquaporins. * **Secretin:** A gastrointestinal hormone stimulated by acidic chyme in the duodenum; it promotes bicarbonate secretion from the pancreas. * **Parathormone (PTH):** Regulated by low ionized serum calcium levels; it acts to increase calcium and decrease phosphate levels. **High-Yield NEET-PG Pearls:** * **Direct Stimulus:** Potassium is the most potent direct stimulus for aldosterone; even a 0.1 mEq/L rise can significantly increase secretion. * **Conn’s Syndrome:** Primary hyperaldosteronism typically presents with the triad of hypertension, hypokalemia, and metabolic alkalosis. * **Inverse Relationship:** While hyperkalemia stimulates aldosterone, aldosterone deficiency (as seen in Addison’s disease) leads to life-threatening hyperkalemia.

Q: Prolactin secretion is increased by all EXCEPT:

Dopamine. **Explanation:** The regulation of prolactin is unique among anterior pituitary hormones because it is under **tonic inhibition** by the hypothalamus. **1. Why Dopamine is the Correct Answer:** Dopamine is the primary **Prolactin-Inhibiting Factor (PIF)**. It is secreted by the tuberoinfundibular dopaminergic (TIDA) neurons into the portal hypophyseal vessels. It acts on **D2 receptors** located on lactotrophs to inhibit the synthesis and secretion of prolactin. Therefore, dopamine *decreases* prolactin levels, making it the correct "EXCEPT" choice. **2. Why the Other Options are Incorrect:** * **Sleep:** Prolactin secretion is pulsatile and follows a diurnal rhythm. Levels rise significantly during sleep (especially non-REM), peaking in the early morning hours. * **Pregnancy:** High levels of estrogen during pregnancy stimulate the hypertrophy and hyperplasia of lactotrophs, leading to a marked increase in prolactin secretion. * **Stress:** Prolactin is considered a "stress hormone." Physical or emotional stress (including exercise, surgery, or hypoglycemia) triggers a rapid release of prolactin via serotonergic and opioid pathways. **High-Yield Clinical Pearls for NEET-PG:** * **TRH Connection:** Thyrotropin-releasing hormone (TRH) acts as a potent prolactin-releasing factor. This explains why patients with **Primary Hypothyroidism** (high TRH) often present with hyperprolactinemia. * **Drug-Induced Hyperprolactinemia:** Any drug that blocks D2 receptors (e.g., Antipsychotics like Haloperidol, or Prokinetics like Metoclopramide) will cause elevated prolactin levels. * **Stalk Effect:** Any pituitary tumor or trauma that compresses the pituitary stalk prevents dopamine from reaching the lactotrophs, leading to increased prolactin (the only hormone that increases when the stalk is cut).

Q: Prolactin secretion is not stimulated by:

Levodopa. **Explanation:** The regulation of prolactin (PRL) is unique among anterior pituitary hormones because it is primarily under **tonic inhibition** by the hypothalamus. The major prolactin-inhibiting factor (PIF) is **Dopamine**, which acts on D2 receptors of the lactotrophs. **Why Levodopa is the Correct Answer:** Levodopa (L-Dopa) is a precursor to dopamine. When administered, it crosses the blood-brain barrier and increases dopamine levels in the brain. Since dopamine inhibits prolactin release, **Levodopa decreases prolactin secretion** rather than stimulating it. Therefore, it is the correct answer as it is an inhibitor. **Analysis of Incorrect Options:** * **Sleep:** Prolactin secretion follows a pulsatile and diurnal rhythm. Levels rise significantly during sleep (especially during non-REM sleep), peaking in the early morning hours. * **Estrogen:** Estrogen stimulates the hypertrophy and hyperplasia of lactotrophs and directly increases prolactin gene expression. This is why prolactin levels are higher in females after puberty. * **Pregnancy:** During pregnancy, high levels of estrogen and progesterone lead to a progressive increase in prolactin levels (up to 10-20 fold) to prepare the mammary glands for lactation. **High-Yield Clinical Pearls for NEET-PG:** * **TRH (Thyrotropin-Releasing Hormone):** While primarily for TSH, TRH is a potent stimulator of prolactin. This explains why patients with **Primary Hypothyroidism** often have hyperprolactinemia. * **Dopamine Antagonists:** Drugs like antipsychotics (Haloperidol) and prokinetics (Metoclopramide) block D2 receptors, leading to hyperprolactinemia and galactorrhea. * **Suckling Reflex:** This is the most potent physiological stimulus for prolactin release, mediated by a neuroendocrine reflex that inhibits dopamine release.

Q: What is true about glucagon?

Has no effect on muscle glycogenolysis. **Explanation:** Glucagon is a catabolic hormone secreted by the **alpha cells of the pancreas**, primarily acting to increase blood glucose levels during fasting or hypoglycemia. **Why Option B is correct:** Glucagon acts specifically on the liver because **skeletal muscle lacks glucagon receptors**. While muscle contains significant glycogen stores, these are reserved for local energy production during exercise. Muscle glycogenolysis is stimulated by epinephrine (via $\beta_2$ receptors) and calcium ions, but not by glucagon. In contrast, glucagon is the primary driver of **hepatic glycogenolysis**. **Analysis of Incorrect Options:** * **A. Hyperglycemia stimulates its release:** Incorrect. Glucagon is inhibited by hyperglycemia and stimulated by **hypoglycemia**. Its primary role is to prevent blood glucose from falling too low. * **C. Stimulates glycolysis:** Incorrect. Glucagon **inhibits glycolysis** (the breakdown of glucose for energy) in the liver to conserve glucose for release into the bloodstream. It does this by decreasing levels of Fructose-2,6-bisphosphate. * **D. Inhibits gluconeogenesis:** Incorrect. Glucagon **stimulates gluconeogenesis** (the synthesis of glucose from non-carbohydrate sources like amino acids) to maintain euglycemia during prolonged fasting. **High-Yield NEET-PG Pearls:** * **Mechanism of Action:** Glucagon acts via a **G-protein coupled receptor (Gs)**, increasing intracellular **cAMP** and activating Protein Kinase A. * **Amino Acids:** Arginine and Alanine *stimulate* glucagon release (this prevents hypoglycemia during a pure protein meal). * **Clinical Use:** Glucagon is the treatment of choice for **Beta-blocker overdose** because it increases cAMP in cardiac tissue independently of beta-receptors.

Question 1

Which of the following statements about the hormone leptin is FALSE?

Accepted Answer

Leptin stimulates appetite.

Answer

Leptin levels are typically increased in obese individuals.

Answer

Leptin exerts its primary action on the hypothalamus.

Answer

Leptin is synthesized and secreted by adipose tissue.

Question 2

Which of the following inhibits the secretion of Growth Hormone (GH)?

Accepted Answer

Hyperglycemia

Answer

Bromocriptine

Answer

Vigorous exercise

Answer

Deep sleep

Question 3

Excessive secretion of ACTH causes which of the following conditions?

Accepted Answer

Cushing's syndrome

Answer

Addison's disease

Answer

Myxoedema

Answer

Thyrotoxicosis

Question 4

A patient sustains a pituitary stalk transection due to an accident. Which of the following physiological responses will NOT occur?

Accepted Answer

Diabetes mellitus

Answer

Diabetes insipidus

Answer

Hyperprolactinemia

Answer

Hypothyroidism

Question 5

Which one of the following makes epiphyseal cartilage matrix fail to calcify?

Accepted Answer

Hypovitaminosis D

Answer

Thyroxine

Answer

Hypervitaminosis A

Answer

Hydrocortisone

Question 6

Hyperkalemia stimulates the secretion of which hormone?

Accepted Answer

Aldosterone

Answer

Antidiuretic hormone (ADH)

Answer

Secretin

Answer

Parathormone

Question 7

Prolactin secretion is increased by all EXCEPT:

Accepted Answer

Dopamine

Answer

Sleep

Answer

Pregnancy

Answer

Stress

Question 8

Prolactin secretion is not stimulated by:

Accepted Answer

Levodopa

Answer

Sleep

Answer

Estrogen

Answer

Pregnancy

Question 9

All of the following are true about osteoclasts except?

Accepted Answer

PTH acts directly on osteoclasts

Answer

Derived from monocytes

Answer

Associated with bone demineralisation

Answer

Can phagocytose foreign bodies

Question 10

What is true about glucagon?

Accepted Answer

Has no effect on muscle glycogenolysis

Answer

Hyperglycemia stimulates its release

Answer

Stimulates glycolysis

Answer

Inhibits gluconeogenesis

Endocrinology — MCQs

Endocrinology — MCQs

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