Endocrinology Practice Questions

Q: In a seriously ill patient, addition of amino acids to the diet results in a positive nitrogen balance. What is the primary mechanism responsible for this effect?

Increased secretion of insulin. **Explanation:** The primary mechanism behind the positive nitrogen balance following amino acid administration is the **anabolic action of insulin**. **Why Option C is Correct:** Amino acids (particularly arginine and leucine) are potent secretagogues for the pancreas. When amino acids enter the bloodstream, they stimulate the **β-cells of the Islets of Langerhans** to secrete insulin. Insulin is a powerful anabolic hormone that: 1. Increases the cellular uptake of amino acids into skeletal muscle. 2. Stimulates ribosomal protein synthesis. 3. Inhibits intracellular protein catabolism (proteolysis). By shifting the balance toward protein synthesis and away from breakdown, insulin induces a **positive nitrogen balance**. **Why Other Options are Incorrect:** * **Option A:** While absorption is necessary for amino acids to enter the system, it is a transport process, not the metabolic mechanism that dictates nitrogen balance. * **Option B:** Gluconeogenesis is a **catabolic** process where amino acids (glucogenic) are broken down to produce glucose. This would lead to a *negative* nitrogen balance and increased urea production. * **Option C:** While GH is anabolic, its secretion is primarily stimulated by hypoglycemia, fasting, or specific amino acids (like Arginine) during sleep/exercise. However, in the context of dietary intake, the immediate and dominant metabolic driver for protein accretion is insulin. **High-Yield NEET-PG Pearls:** * **Positive Nitrogen Balance:** Seen in growing children, pregnancy, and recovery from illness. * **Negative Nitrogen Balance:** Seen in starvation, severe burns, uncontrolled diabetes, and major trauma (due to cortisol and catecholamines). * **Insulin vs. Glucagon:** Insulin is the only hormone that lowers blood glucose while simultaneously promoting protein storage. Glucagon, conversely, promotes gluconeogenesis and ureagenesis.

Q: Central diabetes insipidus is characterized by?

Low urine and high plasma osmolality. **Explanation:** Central Diabetes Insipidus (CDI) is caused by a deficiency in the production or secretion of **Antidiuretic Hormone (ADH)** from the posterior pituitary. ADH normally acts on the V2 receptors in the collecting ducts of the kidney to reabsorb water. 1. **Why Option D is correct:** In the absence of ADH, the kidneys cannot reabsorb water, leading to the excretion of large volumes of dilute urine. This results in **low urine osmolality** (typically <200 mOsm/kg). The excessive loss of free water leads to hemoconcentration, resulting in **high plasma osmolality** (hypernatremia). 2. **Why other options are incorrect:** * **Option A:** Low plasma osmolality is seen in Primary Polydipsia (excessive water intake). * **Option B:** High urine osmolality occurs in dehydration where ADH is functioning normally to conserve water. * **Option C:** This pattern is physiologically impossible in DI; if urine osmolality is high, the body is conserving water, which would lower plasma osmolality. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** The **Water Deprivation Test**. In CDI, urine osmolality remains low despite dehydration but increases significantly (>50%) after administering exogenous desmopressin (differentiating it from Nephrogenic DI). * **Treatment of Choice:** Desmopressin (DDAVP), a synthetic ADH analogue. * **Most common cause:** Idiopathic, followed by head trauma or neurosurgery (transsphenoidal surgery). * **Triphasic Response:** Post-trauma/surgery, patients may show: DI phase → SIADH phase → Permanent DI phase.

Q: Which of the following hormones shares a common beta subunit with TSH?

None of the above. **Explanation:** The correct answer is **None of the above** because the question asks which hormone shares a **beta (β) subunit** with TSH. In endocrinology, it is a fundamental concept that the glycoprotein hormone family—consisting of **TSH, LH, FSH, and hCG**—shares an **identical alpha (α) subunit**. 1. **The Concept of Subunits:** These hormones are heterodimers. The **alpha (α) subunit** is common to all four (encoded by the same gene), whereas the **beta (β) subunit** is unique to each hormone. The beta subunit is what confers **biological specificity** and determines the specific receptor binding and physiological action. 2. **Why Options A and B are Incorrect:** LH and FSH share the same alpha subunit as TSH, but they have their own distinct beta subunits (LH-β and FSH-β). Therefore, they do not share a beta subunit with TSH. 3. **Why Option C is Incorrect:** ACTH is a polypeptide derived from the precursor molecule **POMC** (Pro-opiomelanocortin). It is not a glycoprotein and does not possess alpha or beta subunits. **High-Yield Clinical Pearls for NEET-PG:** * **Cross-reactivity:** Because hCG shares the same alpha subunit and a very similar beta subunit to TSH, extremely high levels of hCG (as seen in Hydatidiform mole or Choriocarcinoma) can weakly bind to TSH receptors, potentially causing **hyperthyroidism**. * **Pregnancy Tests:** Pregnancy tests specifically use antibodies against the **beta-subunit of hCG** to avoid cross-reactivity with LH, FSH, or TSH. * **Commonality:** Remember the mnemonic **"F-L-A-T"** (FSH, LH, ACTH, TSH) for anterior pituitary hormones, but distinguish that only FSH, LH, and TSH (plus placental hCG) are the glycoproteins with shared alpha subunits.

Q: Which of the following conditions leads to an increase in the calcium content of bone?

Estrogen supplementation in post-menopausal women. ### Explanation The correct answer is **D. Estrogen supplementation in post-menopausal women.** **Why it is correct:** Estrogen plays a critical role in maintaining bone mineral density (BMD) by inhibiting bone resorption. It achieves this through two primary mechanisms: 1. **Inhibition of Osteoclasts:** Estrogen induces apoptosis of osteoclasts and decreases their activity. 2. **RANKL/OPG Pathway:** It decreases the expression of **RANKL** (which activates osteoclasts) and increases the production of **Osteoprotegerin (OPG)**, a decoy receptor that prevents RANKL from binding to its receptor. In post-menopausal women, estrogen deficiency leads to accelerated bone loss; therefore, supplementation helps shift the balance toward bone formation/retention, increasing the calcium content of the bone. **Why the other options are incorrect:** * **A. Prolonged immobilization:** Lack of mechanical stress on bones leads to increased osteoclast activity and decreased osteoblast activity (disuse atrophy), resulting in calcium loss from bones and hypercalciuria. * **B. Glucocorticoid administration:** Steroids cause osteoporosis by inhibiting osteoblast function, decreasing intestinal calcium absorption, and increasing renal calcium excretion. * **C. Hyperparathyroidism:** Parathyroid hormone (PTH) increases bone resorption to raise serum calcium levels. Chronic elevation leads to significant demineralization (e.g., Osteitis fibrosa cystica). **High-Yield NEET-PG Pearls:** * **OPG/RANKL Ratio:** A high ratio favors bone formation; a low ratio (seen in menopause) favors bone resorption. * **Denosumab:** A monoclonal antibody used in osteoporosis that mimics OPG by binding to RANKL. * **Weight-bearing exercise:** The most physiological way to increase bone calcium content due to the piezoelectric effect on osteoblasts.

Q: In the thyroid gland, the colloid material is predominantly composed of which of the following?

Thyroglobulin. **Explanation:** **1. Why Thyroglobulin is Correct:** The thyroid follicle is the functional unit of the thyroid gland. The central lumen of these follicles is filled with **colloid**, a viscous fluid. The primary constituent of this colloid is **Thyroglobulin (Tg)** [1], a large dimeric glycoprotein synthesized by the follicular epithelial cells. Thyroglobulin acts as a scaffold for thyroid hormone synthesis and a storage form of iodine. It contains tyrosine residues that undergo iodination to eventually form T3 and T4. **2. Why Other Options are Incorrect:** * **Thyroxine (T4):** While T4 is the major hormone produced by the thyroid, it is stored *within* the thyroglobulin molecule in the colloid. It is not the "predominant material" itself but a product cleaved from Tg before secretion into the blood. * **Monoiodotyrosine (MIT) & Diiodotyrosine (DIT):** These are intermediate iodinated tyrosine residues found attached to the thyroglobulin backbone. They are precursors to T3 and T4 and do not exist independently as the bulk of the colloid. **3. High-Yield Clinical Pearls for NEET-PG:** * **PAS Staining:** Thyroid colloid is strongly **PAS (Periodic Acid-Schiff) positive** [1] due to the high carbohydrate content of thyroglobulin. * **Scalloping:** In hyperactive states (like Graves' disease), the colloid shows "peripheral scalloping" or "moth-eaten" appearance due to rapid endocytosis of thyroglobulin by follicular cells. * **Tumor Marker:** Serum thyroglobulin is used as a tumor marker to monitor the recurrence of **Papillary and Follicular thyroid carcinomas** after total thyroidectomy. * **Site of Action:** The coupling of MIT and DIT occurs at the apical surface/colloid interface, catalyzed by **Thyroid Peroxidase (TPO)**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1085-1086.

Q: A man eats a low-carbohydrate meal rich in proteins containing amino acids that stimulate insulin secretion. Which physiological response accounts for the absence of hypoglycemia?

Stimulation of glucagon secretion. **Explanation:** **1. Why the Correct Answer is Right:** When a person consumes a high-protein, low-carbohydrate meal, certain amino acids (specifically arginine and lysine) act as potent secretagogues for **both insulin and glucagon**. Under normal circumstances, insulin lowers blood glucose by promoting peripheral uptake. However, in a low-carbohydrate meal, there is no exogenous glucose to offset this insulin action. To prevent life-threatening hypoglycemia, the pancreas simultaneously secretes **glucagon**. Glucagon stimulates hepatic glycogenolysis and gluconeogenesis, ensuring a steady output of glucose into the bloodstream. This "dual secretion" maintains euglycemia while allowing insulin to perform its primary role in the protein-rich state: promoting amino acid uptake and protein synthesis in muscles. **2. Why Other Options are Incorrect:** * **Options A & B:** Growth Hormone (GH) and Somatomedin C (IGF-1) are actually **stimulated** by amino acids (like arginine) to promote growth and protein synthesis. Suppressing them would not prevent hypoglycemia; in fact, GH is a counter-regulatory hormone that helps raise blood sugar. * **Option C:** While cortisol is a diabetogenic hormone that increases blood glucose, its secretion is primarily regulated by the HPA axis in response to stress or circadian rhythms. It does not show a rapid, acute spike specifically in response to a protein meal to prevent immediate hypoglycemia. **3. NEET-PG High-Yield Pearls:** * **The "Mixed Meal" Concept:** In a mixed meal (Carbs + Protein), insulin rises and glucagon is suppressed. In a pure protein meal, **both rise**. * **Potent Amino Acids:** Arginine is the most potent stimulator of both insulin and glucagon. * **Glucagon’s Primary Target:** The liver (glycogenolysis). It has no significant effect on muscle glycogen. * **Insulin/Glucagon Ratio:** This ratio determines the net metabolic state (Anabolic vs. Catabolic).

Q: The syndrome of growth failure, rash, and hypogonadism is due to deficiency of which essential nutrient?

Zinc. **Explanation:** The correct answer is **Zinc (Option C)**. Zinc is an essential trace element that acts as a cofactor for over 300 enzymes, including those involved in DNA synthesis, protein metabolism, and cell division. **Why Zinc is correct:** Zinc deficiency classically presents with a triad of **growth retardation (stunting)**, **hypogonadism (delayed sexual maturation)**, and **dermatitis**. * **Growth Failure:** Zinc is vital for the action of Growth Hormone and IGF-1. * **Hypogonadism:** It is essential for testosterone production and spermatogenesis. * **Rash:** Deficiency leads to a characteristic periorificial and acral dermatitis (classically seen in the genetic disorder *Acrodermatitis Enteropathica*). It also causes impaired wound healing and immune dysfunction. **Why other options are incorrect:** * **Calcium:** Deficiency primarily leads to rickets in children, osteomalacia in adults, and tetany due to neuromuscular irritability, but not typically a specific rash or hypogonadism. * **Copper:** Deficiency causes microcytic anemia (refractory to iron), neutropenia, and skeletal abnormalities. *Menkes Kinky Hair Syndrome* is the classic genetic deficiency. * **Magnesium:** Deficiency results in neuromuscular irritability (tremors, seizures) and cardiac arrhythmias, often associated with hypocalcemia and hypokalemia. **High-Yield Clinical Pearls for NEET-PG:** * **Acrodermatitis Enteropathica:** An autosomal recessive disorder of zinc absorption. * **Zinc & Taste:** Deficiency causes **hypogeusia** (decreased taste acuity). * **Zinc & Vision:** It is required for the enzyme retinol dehydrogenase; deficiency can contribute to night blindness. * **Diarrhea:** Zinc supplementation is a WHO-recommended standard of care to reduce the duration and severity of pediatric diarrhea.

Q: Triiodothyronine (T3) as compared to T4:

Is shorter acting. **Explanation:** The thyroid gland primarily secretes **Thyroxine (T4)**, which acts as a pro-hormone, while **Triiodothyronine (T3)** is the biologically active form. The differences in their pharmacokinetics and pharmacodynamics are high-yield topics for NEET-PG. **Why the correct answer is right:** T3 is **shorter acting** because it has a significantly lower affinity for plasma proteins (like Thyroxine-Binding Globulin) compared to T4. This results in a much shorter **half-life** (approx. 1 day for T3 vs. 6–7 days for T4). Because it is not "stored" in the blood by proteins, it is cleared and metabolized more rapidly. **Analysis of Incorrect Options:** * **A. Is more plasma protein bound:** Incorrect. T4 is 99.98% bound, whereas T3 is only 99.8% bound. The higher free fraction of T3 contributes to its rapid action and clearance. * **C. Is less potent:** Incorrect. T3 is **3 to 5 times more potent** than T4. It has a much higher affinity for the nuclear thyroid hormone receptors. * **D. Has delayed action:** Incorrect. T3 has a **rapid onset of action** (latent period of 6–12 hours) compared to T4 (latent period of 2–3 days). **High-Yield Clinical Pearls for NEET-PG:** * **Peripheral Conversion:** About 80% of T3 is derived from the peripheral deiodination of T4 by the enzyme **5'-deiodinase**. * **Reverse T3 (rT3):** This is the metabolically inactive form produced during states of illness or starvation. * **Potency vs. Quantity:** T4 is secreted in larger quantities (ratio 20:1), but T3 is the functional mediator of metabolic effects. * **Thyroid Storm:** Proportions of T3 increase significantly, necessitating rapid-acting treatments like PTU which also inhibits peripheral conversion.

Q: All of the following statements concerning Atrial Natriuretic Peptide (ANP) are true except:

Its effects are mediated by decreased cyclic AMP. **Explanation:** The correct answer is **D** because the effects of Atrial Natriuretic Peptide (ANP) are mediated by an **increase in cyclic GMP (cGMP)**, not a decrease in cAMP. ANP binds to its receptor (NPR-A), which has intrinsic **guanylyl cyclase** activity. This converts GTP to cGMP, which then activates Protein Kinase G (PKG) to produce physiological effects like vasodilation and natriuresis. **Analysis of Options:** * **Option A (Incorrect):** This is a true statement. The primary stimulus for ANP release is the **stretching of atrial myocytes** caused by increased blood volume or high atrial pressure. * **Option B (Incorrect):** This is a true statement. ANP increases GFR by **dilating afferent arterioles** and **constricting efferent arterioles**. It also increases the capillary surface area for filtration by relaxing glomerular mesangial cells. * **Option C (Incorrect):** This is a true statement. ANP acts as a natural antagonist to the Renin-Angiotensin-Aldosterone System (RAAS). It directly inhibits the release of **renin** from juxtaglomerular cells and **aldosterone** from the adrenal cortex. **High-Yield Clinical Pearls for NEET-PG:** * **Second Messenger:** ANP and Nitric Oxide (NO) both use **cGMP** as a second messenger. * **Brain Natriuretic Peptide (BNP):** Secreted by ventricles in response to pressure overload; used clinically as a marker for **Congestive Heart Failure (CHF)**. * **Nesiritide:** A recombinant form of BNP used in the treatment of acute decompensated heart failure. * **Net Effect:** ANP is "heart-protective" as it lowers blood pressure and reduces fluid volume (natriuresis and diuresis).

Question 1

In a seriously ill patient, addition of amino acids to the diet results in a positive nitrogen balance. What is the primary mechanism responsible for this effect?

Accepted Answer

Increased secretion of insulin

Answer

Increased absorption of amino acids from the intestine

Answer

Enhanced rates of gluconeogenesis

Answer

Increased Growth hormone secretion

Question 2

Central diabetes insipidus is characterized by?

Accepted Answer

Low urine and high plasma osmolality

Answer

Low plasma and low urine osmolality

Answer

High plasma and high urine osmolality

Answer

Low plasma and high urine osmolality

Question 3

Which of the following hormones shares a common beta subunit with TSH?

Accepted Answer

None of the above

Answer

LH

Answer

FSH

Answer

ACTH

Question 4

Which of the following conditions leads to an increase in the calcium content of bone?

Accepted Answer

Estrogen supplementation in post-menopausal women

Answer

Prolonged immobilization

Answer

Glucocorticoid administration

Answer

Hyperparathyroidism

Question 5

In the thyroid gland, the colloid material is predominantly composed of which of the following?

Accepted Answer

Thyroglobulin

Answer

Thyroxine

Answer

Monoiodotyrosine

Answer

Diiodotyrosine

Question 6

A man eats a low-carbohydrate meal rich in proteins containing amino acids that stimulate insulin secretion. Which physiological response accounts for the absence of hypoglycemia?

Accepted Answer

Stimulation of glucagon secretion

Answer

Suppression of growth hormone (GH) secretion

Answer

Suppression of somatomedin C secretion

Answer

Stimulation of cortisol secretion

Question 7

The syndrome of growth failure, rash, and hypogonadism is due to deficiency of which essential nutrient?

Accepted Answer

Zinc

Answer

Calcium

Answer

Copper

Answer

Magnesium

Question 8

Triiodothyronine (T3) as compared to T4:

Accepted Answer

Is shorter acting

Answer

Is more plasma protein bound

Answer

Is less potent

Answer

Has delayed action

Question 9

Insulin acts on glucose metabolism by:

Accepted Answer

Increasing glucose permeability across cell membrane against the glucose gradient

Answer

Increasing glucose permeability across cell membrane

Answer

Increasing glucose permeability of renal cells

Answer

Increasing glucose transport to the brain

Question 10

All of the following statements concerning Atrial Natriuretic Peptide (ANP) are true except:

Accepted Answer

Its effects are mediated by decreased cyclic AMP

Answer

Its secretion is increased by an increase in blood volume

Answer

It increases glomerular filtration rate

Answer

It inhibits renin secretion

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?