Endocrinology Practice Questions

Q: Which of the following statements regarding ghrelin is false?

None of the above. **Explanation:** Ghrelin, often referred to as the "hunger hormone," is a 28-amino acid peptide that plays a central role in energy homeostasis. The correct answer is **None of the above** because all statements (A, B, and C) are physiologically accurate. 1. **Secreted from D1 cells (Option A):** Ghrelin is primarily synthesized and secreted by the **P/D1 cells** (oxyntic cells) located in the fundus of the stomach. Smaller amounts are produced in the small intestine and the epsilon cells of the pancreas. 2. **Induces Lipolysis (Option B):** While ghrelin is orexigenic (promotes fat storage in the long term), it acutely stimulates the secretion of **Growth Hormone (GH)** from the anterior pituitary by binding to the Growth Hormone Secretagogue Receptor (GHSR). Growth hormone is a potent lipolytic agent, thereby indirectly inducing lipolysis. 3. **Stimulates Appetite (Option C):** Ghrelin is the only peripheral hormone known to stimulate food intake. It acts on the **Arcuate Nucleus** of the hypothalamus, specifically stimulating **NPY (Neuropeptide Y)** and **AgRP (Agouti-related peptide)** neurons to increase hunger. **High-Yield NEET-PG Pearls:** * **Prader-Willi Syndrome:** Characterized by extremely high ghrelin levels, leading to hyperphagia and obesity. * **Sleep Deprivation:** Increases ghrelin and decreases leptin, contributing to weight gain. * **Post-Gastric Bypass:** Ghrelin levels significantly drop, which is one mechanism for the rapid weight loss observed after bariatric surgery. * **Opponent Hormone:** **Leptin** (secreted by adipocytes) is the functional antagonist of ghrelin, as it induces satiety.

Q: Which of the following conditions would be associated with parallel changes in aldosterone and cortisol secretion?

Addison's disease. **Explanation:** The adrenal cortex is divided into three zones: the **Zona Glomerulosa** (produces Aldosterone/Mineralocorticoids) and the **Zona Fasciculata/Reticularis** (produces Cortisol/Glucocorticoids and Androgens). **Why Addison’s Disease is correct:** Addison’s disease (Primary Adrenocortical Insufficiency) involves the **destruction of the entire adrenal cortex** (most commonly due to autoimmune adrenalitis or TB). Because the whole gland is affected, there is a simultaneous deficiency of both aldosterone and cortisol. Thus, they change in **parallel** (both decrease). **Why the other options are incorrect:** * **Cushing’s Disease:** This is a secondary hypercortisolism caused by a pituitary adenoma secreting excess ACTH. ACTH primarily regulates cortisol; it has minimal effect on aldosterone (which is regulated by the Renin-Angiotensin System). Therefore, cortisol increases while aldosterone remains relatively normal. * **Cushing’s Syndrome:** This refers to hypercortisolism from any cause (e.g., adrenal tumor or exogenous steroids). Similar to Cushing's disease, the pathology is specific to glucocorticoid excess, not mineralocorticoids. * **Conn’s Syndrome:** This is Primary Hyperaldosteronism (usually a Z. Glomerulosa adenoma). It results in isolated high aldosterone levels; cortisol levels remain normal. **High-Yield Clinical Pearls for NEET-PG:** * **Regulation:** Aldosterone is primarily regulated by **Angiotensin II and Serum Potassium**, whereas Cortisol is regulated by **ACTH**. * **Electrolytes in Addison’s:** Look for the triad of **Hyponatremia, Hyperkalemia, and Metabolic Acidosis** (due to aldosterone deficiency) along with hypoglycemia (due to cortisol deficiency). * **Hyperpigmentation:** Seen in Addison’s (Primary) but NOT in Secondary Adrenal Insufficiency, due to high ACTH/MSH levels.

Q: What is the primary form of cortisol in plasma?

Bound to corticosteroid-binding globulin (CBG). ### Explanation **1. Why Option D is Correct:** Cortisol, being a steroid hormone, is lipophilic and requires transport proteins to travel through the aqueous environment of the plasma. In humans, approximately **75% to 80%** of circulating cortisol is bound to **Corticosteroid-Binding Globulin (CBG)**, also known as **Transcortin**. This high-affinity binding serves as a reservoir, protecting the hormone from rapid metabolic degradation by the liver and excretion by the kidneys, thereby extending its half-life. **2. Why Other Options are Incorrect:** * **Option A (Albumin):** About **15%** of cortisol is bound to albumin. While albumin has a high capacity, it has a much lower affinity for cortisol compared to CBG. * **Option B (Transthyretin):** Transthyretin (Prealbumin) is primarily involved in the transport of Thyroxine (T4) and Retinol (Vitamin A), not cortisol. * **Option C (Free in solution):** Only about **5% to 10%** of cortisol exists in the "free" or unbound state. However, this free fraction is the biologically active form capable of crossing cell membranes to bind to intracellular receptors. **3. NEET-PG High-Yield Clinical Pearls:** * **CBG Levels:** CBG synthesis in the liver is **increased by Estrogen** (e.g., pregnancy, OCP use) and **decreased in Liver Cirrhosis** or Nephrotic Syndrome. * **Total vs. Free Cortisol:** In pregnancy, total cortisol levels rise due to increased CBG, but the "free" (active) cortisol remains relatively normal, maintaining homeostasis. * **Diurnal Variation:** Cortisol levels peak in the early morning (approx. 8 AM) and reach their nadir around midnight. * **Metabolism:** Cortisol is metabolized in the liver and excreted in the urine as **17-hydroxycorticosteroids**.

Q: Normal thyroid weight varies with dietary iodine content?

Inversely. **Explanation:** The size and weight of the thyroid gland are primarily regulated by **Thyroid Stimulating Hormone (TSH)**. The relationship between dietary iodine and thyroid weight is **inversely proportional** due to the negative feedback loop of the Hypothalamic-Pituitary-Thyroid (HPT) axis. 1. **Why "Inversely" is correct:** When dietary iodine intake is low, the thyroid cannot produce sufficient T3 and T4. This lack of negative feedback causes the anterior pituitary to secrete more TSH. TSH acts as a growth factor, causing hypertrophy and hyperplasia of thyroid follicular cells to maximize iodine uptake. This results in an increase in thyroid weight (Goiter). Conversely, adequate iodine intake maintains normal TSH levels and normal gland weight. 2. **Why other options are wrong:** * **Directly proportional:** This would imply that more iodine leads to a larger gland, which is physiologically incorrect (except in rare cases of Jod-Basedow phenomenon, which is a pathological state, not a normal physiological variation). * **Inverse cubically:** There is no mathematical cubic relationship described in physiological literature for this mechanism. * **Not fixed:** While thyroid weight does vary, it follows a specific physiological pattern rather than being random or "not fixed." **High-Yield Clinical Pearls for NEET-PG:** * **Normal Thyroid Weight:** Approximately 15–25 grams in adults (varies by region). * **Wolff-Chaikoff Effect:** A transient reduction in thyroid hormone synthesis following ingestion of a large load of iodine. * **Goitrogens:** Substances (like cabbage, turnips, or cassava) that interfere with iodine uptake, leading to increased TSH and increased thyroid weight. * **Daily Iodine Requirement:** ~150 μg/day for adults; higher (220–290 μg/day) during pregnancy and lactation.

Q: Which of the following statements regarding calcitonin is FALSE?

Its actions are similar to parathyroid hormone.. **Explanation** The correct answer is **D** because Calcitonin and Parathyroid Hormone (PTH) are **physiological antagonists**. While PTH acts to increase serum calcium levels (hypercalcemic hormone), Calcitonin acts to decrease them (hypocalcemic hormone). **Why Option D is False:** Calcitonin and PTH have opposing effects on bone and kidneys. PTH stimulates osteoclasts to resorb bone and increases renal calcium reabsorption. In contrast, Calcitonin inhibits bone resorption and promotes renal calcium excretion. **Analysis of Other Options:** * **Option A:** Calcitonin is used for the acute management of hypercalcemic crisis. However, its effect is short-lived due to **"tachyphylaxis"** (downregulation of receptors), making it unsuitable for long-term therapy. * **Option B:** The primary mechanism of Calcitonin is the direct inhibition of **osteoclasts**, which reduces the release of calcium and phosphate from the bone matrix into the plasma. * **Option C:** Calcitonin is secreted by the **Parafollicular cells (C-cells)** of the thyroid. Medullary Thyroid Carcinoma (MTC) originates from these cells; thus, serum Calcitonin serves as a specific tumor marker for diagnosis and monitoring recurrence. **High-Yield Clinical Pearls for NEET-PG:** * **Major Stimulus:** An increase in plasma calcium concentration is the primary stimulus for Calcitonin secretion. * **Salmon Calcitonin:** Used therapeutically (e.g., in Paget’s disease) because it is more potent and has a longer half-life than human calcitonin. * **Bone Sparing:** Unlike PTH, Calcitonin is "bone-sparing" and is sometimes used in the treatment of osteoporosis to reduce vertebral fractures.

Q: Melatonin is associated with all of the following except?

Vomiting. **Explanation:** Melatonin is a hormone synthesized by the **pineal gland** (derived from the amino acid Tryptophan) and is primarily responsible for regulating the body's **circadian rhythm**. **Why 'Vomiting' is the correct answer:** Melatonin has no physiological or clinical association with the induction or regulation of vomiting. Vomiting is controlled by the Area Postrema (Chemoreceptor Trigger Zone) in the medulla oblongata, which responds to dopamine, serotonin (5-HT3), and substance P, but not melatonin. **Analysis of other options:** * **Sleep mechanism:** Melatonin is known as the "hormone of darkness." Its secretion increases in the dark, signaling the body to prepare for sleep. It acts on MT1 and MT2 receptors in the Suprachiasmatic Nucleus (SCN) of the hypothalamus. * **Jetlag:** Exogenous melatonin is a standard treatment for jetlag. It helps "reset" the internal biological clock when traveling across time zones by shifting the circadian phase. * **Pituitary gland secretion:** Melatonin exerts an inhibitory effect on the hypothalamic-pituitary-gonadal axis. It inhibits the release of GnRH, thereby decreasing the secretion of LH and FSH from the anterior pituitary. This is why pineal tumors (which may decrease melatonin) can lead to precocious puberty. **High-Yield Clinical Pearls for NEET-PG:** * **Precursor:** Tryptophan → Serotonin → Melatonin. * **Rate-limiting enzyme:** N-acetyltransferase (activity peaks at night). * **Light inhibition:** Light hitting the retina inhibits the pineal gland via the retinohypothalamic tract. * **Clinical Use:** Used in delayed sleep phase syndrome and for blind individuals to regulate sleep-wake cycles.

Q: Which of the following hormones does NOT modify growth?

Vasopressin. **Explanation:** Growth is a complex physiological process regulated by a specific set of hormones that influence protein synthesis, cell division, and skeletal maturation. **Why Vasopressin is the Correct Answer:** **Vasopressin (Antidiuretic Hormone/ADH)** is primarily involved in water homeostasis and vascular tone. It acts on the V2 receptors in the renal collecting ducts to increase water reabsorption and V1 receptors to cause vasoconstriction. It has **no physiological role** in stimulating or modifying systemic growth or skeletal development. **Analysis of Other Options:** * **Growth Hormone (GH) / Corticotrophin:** GH is the primary stimulator of postnatal growth via IGF-1. Corticotrophin (ACTH) influences growth indirectly; while essential in physiological amounts, chronic excess (Cushing’s) actually inhibits growth by antagonizing GH and causing protein catabolism. * **Insulin:** Insulin is a potent growth promoter, especially during **fetal development**. It stimulates amino acid uptake and protein synthesis. Children with insulin deficiency (Type 1 Diabetes) often exhibit stunted growth (Mauriac syndrome). * **Prolactin:** Prolactin belongs to the same structural family as Growth Hormone. While its primary role is lactation, it has weak GH-like effects and can influence the proliferation of specific tissues, including immune cells and mammary tissue. **High-Yield Clinical Pearls for NEET-PG:** * **Fetal Growth:** Primarily regulated by **Insulin** and **IGF-2**. Growth Hormone is *not* essential for intrauterine growth. * **Postnatal Growth:** Primarily regulated by **GH, IGF-1, and Thyroid hormones**. * **Pubertal Growth Spurt:** Driven by the synergistic action of **Androgens/Estrogens** and GH. * **Thyroid Hormone:** Essential for bone maturation and CNS development; deficiency leads to cretinism (stunted growth and mental retardation).

Q: Which of the following is NOT an adverse effect of excessive mineralocorticoid action?

Acidosis. Mineralocorticoids (primarily **Aldosterone**) act on the mineralocorticoid receptors in the principal cells and intercalated cells of the late distal tubule and collecting duct. **Why Acidosis is the Correct Answer:** Excessive mineralocorticoid action leads to **Alkalosis**, not acidosis. Aldosterone stimulates the secretion of Hydrogen ions ($H^+$) into the tubular lumen via $H^+$-ATPase pumps in the alpha-intercalated cells. Increased loss of $H^+$ in the urine results in **Metabolic Alkalosis**. Therefore, acidosis is the incorrect physiological effect. **Explanation of Incorrect Options:** * **A. Sodium and water retention:** Aldosterone increases the expression of ENaC (Epithelial Sodium Channels) in the principal cells, promoting $Na^+$ reabsorption. Water follows osmotically, leading to volume expansion. * **D. Rise in blood pressure:** Chronic sodium and water retention, coupled with increased peripheral vascular resistance, leads to secondary hypertension. * **C. Aggravation of CHF associated myocardial fibrosis:** Beyond electrolyte balance, aldosterone has "non-genomic" effects. It promotes fibroblast proliferation and collagen deposition in the heart. This is why Mineralocorticoid Receptor Antagonists (MRAs) like **Spironolactone** and **Eplerenone** are mortality-benefit drugs in Heart Failure. **High-Yield NEET-PG Pearls:** * **Conn’s Syndrome:** Primary hyperaldosteronism characterized by the triad of **Hypertension, Hypokalemia, and Metabolic Alkalosis.** * **Escape Phenomenon:** In primary hyperaldosteronism, edema is usually absent because the body "escapes" the sodium-retaining effects via ANP (Atrial Natriuretic Peptide) release. * **Drug of Choice:** Spironolactone is the drug of choice for hepatic cirrhosis with ascites and Conn’s syndrome.

Question 1

Which of the following statements regarding ghrelin is false?

Accepted Answer

None of the above

Answer

Secreted from D1 cells of the fundus

Answer

Induces lipolysis

Answer

Stimulates appetite

Question 2

Which of the following conditions would be associated with parallel changes in aldosterone and cortisol secretion?

Accepted Answer

Addison's disease

Answer

Cushing's disease

Answer

Cushing's syndrome

Answer

Conn's syndrome

Question 3

Which of the following is an example of a neurohormone?

Accepted Answer

Oxytocin

Answer

ACTH

Answer

Cortisol

Answer

Somatostatin

Question 4

What is the primary form of cortisol in plasma?

Accepted Answer

Bound to corticosteroid-binding globulin (CBG)

Answer

Bound to albumin

Answer

Bound to transthyretin

Answer

Free in solution

Question 5

A 43-year-old female presents with galactorrhea. Investigations show increased prolactin levels. Which of the following conditions can cause increased prolactin secretion?

Accepted Answer

Dopamine

Answer

Sleep

Answer

Pregnancy

Answer

Stress

Question 6

Normal thyroid weight varies with dietary iodine content?

Accepted Answer

Inversely

Answer

Directly proportional

Answer

Inverse cubically

Answer

Not fixed

Question 7

Which of the following statements regarding calcitonin is FALSE?

Accepted Answer

Its actions are similar to parathyroid hormone.

Answer

It has a short-term use in patients with hypercalcemia.

Answer

It inhibits osteoclastic activity.

Answer

High concentrations in the plasma are seen in medullary carcinoma of the thyroid.

Question 8

Melatonin is associated with all of the following except?

Accepted Answer

Vomiting

Answer

Pituitary gland secretion

Answer

Sleep mechanism

Answer

Jetlag

Question 9

Which of the following hormones does NOT modify growth?

Accepted Answer

Vasopressin

Answer

Growth hormone / corticotrophin

Answer

Insulin

Answer

Prolactin

Question 10

Which of the following is NOT an adverse effect of excessive mineralocorticoid action?

Accepted Answer

Acidosis

Answer

Sodium and water retention

Answer

Aggravation of CHF associated myocardial fibrosis

Answer

Rise in blood pressure

Endocrinology — MCQs

Endocrinology — MCQs

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