Endocrinology Practice Questions

Q: Decreased plasma renin activity is seen in which of the following conditions?

Primary hyperaldosteronism. **Explanation:** The key to answering this question lies in understanding the **negative feedback loop** of the Renin-Angiotensin-Aldosterone System (RAAS). **1. Why Primary Hyperaldosteronism is correct:** In Primary Hyperaldosteronism (e.g., Conn’s Syndrome), there is autonomous secretion of aldosterone from the adrenal cortex. This excess aldosterone causes sodium and water retention, leading to ECF volume expansion and hypertension. This increased blood pressure and volume are sensed by the juxtaglomerular apparatus, which **suppresses** the release of renin. Therefore, the hallmark of primary hyperaldosteronism is **High Aldosterone with Low Plasma Renin Activity (PRA).** **2. Why the other options are incorrect:** * **Secondary Aldosteronism:** Here, the primary pathology is an overactive RAAS (e.g., renal artery stenosis or congestive heart failure). Increased renin leads to increased aldosterone; thus, **both Renin and Aldosterone are high.** * **Bartter Syndrome:** This is a renal tubular defect (NKCC2 transporter) mimicking chronic loop diuretic use. It leads to salt wasting, volume depletion, and subsequent **activation** of the RAAS, resulting in high renin levels. * **Preeclampsia:** While the pathophysiology is complex, it is generally associated with **increased** renin activity and sensitivity, unlike the suppression seen in primary mineralocorticoid excess. **Clinical Pearls for NEET-PG:** * **Aldosterone-to-Renin Ratio (ARR):** This is the best screening test for Primary Hyperaldosteronism. An **elevated ARR** (High Aldosterone/Low Renin) is diagnostic. * **Liddle’s Syndrome:** This also presents with low renin and hypertension (pseudohyperaldosteronism) but, unlike Conn’s, it features **low aldosterone** levels due to constitutive activation of ENaC channels. * **Hypokalemia and Metabolic Alkalosis** are common laboratory findings in states of mineralocorticoid excess.

Q: Angiotensinogen is secreted by which organ?

Liver. **Explanation:** The correct answer is **Liver**. Angiotensinogen is a large $\alpha_2$-globulin protein (a type of non-specific transport protein) that is constitutively synthesized and secreted into the plasma by the **liver**. It serves as the essential precursor substrate in the Renin-Angiotensin-Aldosterone System (RAAS). **Why other options are incorrect:** * **Kidney:** The kidney (specifically the Juxtaglomerular cells) secretes **Renin**, which is the enzyme that cleaves Angiotensinogen into Angiotensin I. It does not produce the substrate itself. * **Lung:** The lungs are the primary site for **Angiotensin-Converting Enzyme (ACE)**, located on the surface of pulmonary capillary endothelial cells. ACE converts Angiotensin I into the active vasoconstrictor Angiotensin II. * **Brain:** While some local RAAS components exist in the brain for blood pressure regulation, it is not the primary source of circulating Angiotensinogen. **High-Yield NEET-PG Pearls:** 1. **Rate-Limiting Step:** The reaction between Renin and Angiotensinogen is the rate-limiting step of the RAAS cascade. 2. **Hormonal Regulation:** Angiotensinogen levels are increased by **estrogens, glucocorticoids, thyroid hormones, and Angiotensin II**. This explains why oral contraceptive pills (containing estrogen) can sometimes cause secondary hypertension. 3. **Site Summary:** * **Liver:** Angiotensinogen * **Kidney (JG cells):** Renin * **Lungs:** ACE * **Adrenal Cortex (Zona Glomerulosa):** Aldosterone (stimulated by Angiotensin II)

Q: All of the following hormones are secreted by the adrenal cortex EXCEPT:

Estriol. **Explanation:** The adrenal cortex is organized into three distinct zones, each responsible for secreting specific steroid hormones derived from cholesterol (the "GFR" mnemonic): 1. **Zona Glomerulosa:** Secretes Mineralocorticoids (e.g., **Aldosterone**). 2. **Zona Fasciculata:** Secretes Glucocorticoids (e.g., **Cortisol** and **Corticosterone**). 3. **Zona Reticularis:** Secretes Androgens (e.g., Dehydroepiandrosterone/DHEA and Androstenedione). **Why Estriol is the correct answer:** While the adrenal cortex produces weak androgens (DHEA) which can be peripherally converted into estrogens (estrone/estradiol), it does **not** directly secrete **Estriol**. Estriol (E3) is primarily a product of the **placenta** during pregnancy, requiring precursors from both the fetal liver and the adrenal glands. In non-pregnant states, it is a metabolic byproduct of estradiol and estrone. **Analysis of Incorrect Options:** * **Cortisol:** The primary glucocorticoid in humans, synthesized in the Zona Fasciculata. * **Corticosterone:** A glucocorticoid precursor and a minor glucocorticoid secreted by the Zona Fasciculata. In some species, it is the primary glucocorticoid. * **Aldosterone:** The main mineralocorticoid responsible for sodium retention and potassium excretion, synthesized in the Zona Glomerulosa. **High-Yield NEET-PG Pearls:** * **Rate-limiting step:** The conversion of cholesterol to pregnenolone by the enzyme **Desmolase** (stimulated by ACTH). * **Enzyme Deficiency:** 21-Hydroxylase deficiency is the most common cause of Congenital Adrenal Hyperplasia (CAH), leading to decreased cortisol/aldosterone and increased androgens. * **Estrogen Potency:** Estradiol (E2) > Estrone (E1) > Estriol (E3). Estriol is the hallmark of fetal well-being during pregnancy.

Q: Which of the following factors determines whether a patient develops acromegaly or gigantism?

Age at onset of the tumor. The clinical manifestation of growth hormone (GH) excess is primarily determined by the **status of the epiphyseal plates** at the time of onset [1]. ### Why the Correct Answer is Right: * **Gigantism:** Occurs when GH hypersecretion begins **before the fusion of the epiphyses** (pre-pubertal) [1]. Excessive GH stimulates the open growth plates of long bones, leading to dramatic longitudinal growth and tall stature [1]. * **Acromegaly:** Occurs when GH hypersecretion begins **after the fusion of the epiphyses** (post-pubertal) [1]. Since longitudinal growth is no longer possible, the excess GH causes appositional bone growth (thickening), leading to characteristic features like frontal bossing, enlarged hands/feet (acral enlargement), and macroglossia [1]. ### Why Other Options are Wrong: * **Sex:** GH excess affects both males and females similarly; gender does not dictate the clinical entity (gigantism vs. acromegaly). * **Amount of available calcium:** While GH affects bone metabolism, calcium levels do not determine the pattern of skeletal growth. * **Degree of function of the tumor:** The quantity of GH produced influences the severity of symptoms, but the *type* of skeletal deformity is strictly dependent on whether the bones are still capable of linear growth [1]. ### High-Yield Clinical Pearls for NEET-PG: * **Most common cause:** Somatotroph adenoma of the anterior pituitary. * **Best Screening Test:** Serum **IGF-1** levels (more stable than pulsatile GH) [2]. * **Confirmatory Test:** Oral Glucose Tolerance Test (**OGTT**) – failure to suppress GH below 1 ng/mL (or 0.4 ng/mL in newer assays) after 75g glucose [2]. * **Most common cause of death:** Cardiovascular disease (specifically cardiomyopathy). * **Associated condition:** Increased risk of **Colonic Polyps** and Adenocarcinoma [2].

Q: Parathyroid hormone is responsible for all actions except:

Increase in phosphorous absorption. **Explanation:** The primary function of **Parathyroid Hormone (PTH)** is to maintain serum ionized calcium levels. It achieves this through direct actions on the bone and kidneys, and indirect actions on the intestine [1]. **Why Option A is correct:** PTH actually **decreases** serum phosphorus levels [2]. While PTH increases phosphorus mobilization from the bone, its most potent effect occurs in the **proximal convoluted tubule (PCT)** of the kidney, where it inhibits the Na⁺-K⁺-phosphorus cotransporter [1]. This leads to **phosphaturia** (increased excretion of phosphorus in urine) [4]. Therefore, PTH is a phosphaturic hormone, not one that increases its net absorption/retention. **Analysis of incorrect options:** * **Option B & D:** PTH stimulates the enzyme **1-alpha-hydroxylase** in the kidneys, which converts inactive Vitamin D to its active form, **Calcitriol (1,25-DHCC)** [1]. Calcitriol then acts on the intestines to increase the absorption of both Calcium and Vitamin D (via feedback) and Phosphorus [3]. Thus, PTH increases intestinal calcium absorption *indirectly*. * **Option C:** PTH stimulates osteoclasts (via RANKL signaling on osteoblasts) to resorb bone matrix, releasing calcium into the bloodstream [1]. **NEET-PG High-Yield Pearls:** * **Mnemonic for PTH:** "P" stands for **P**hosphaturic (it "Pees" out Phosphate). * **Site of Action:** PTH acts on the **PCT** to inhibit phosphate reabsorption and on the **DCT (Distal Convoluted Tubule)** to increase calcium reabsorption [1]. * **Secondary Hyperparathyroidism:** Commonly seen in Chronic Kidney Disease (CKD) due to phosphate retention and failure of Vitamin D activation [2].

Q: Which hormone(s) utilize the cyclic adenosine monophosphate (cAMP) as a second messenger system?

Calcitonin. **Explanation:** The mechanism of hormone action is a high-yield topic for NEET-PG. Hormones that are water-soluble (peptides and catecholamines) cannot cross the lipid bilayer and must bind to cell surface receptors, triggering **second messenger systems**. **1. Why Calcitonin is Correct:** Calcitonin, secreted by the parafollicular (C-cells) of the thyroid, binds to G-protein coupled receptors (GPCRs). This activates the enzyme **Adenylate Cyclase**, which converts ATP into **cyclic AMP (cAMP)**. Other major hormones using this pathway include ACTH, Glucagon, TSH, PTH, and ADH (via V2 receptors). **2. Why Incorrect Options are Wrong:** * **Angiotensin-Converting Enzyme (ACE):** This is an **enzyme**, not a hormone. It converts Angiotensin I to Angiotensin II. While Angiotensin II is a hormone, it primarily utilizes the **IP3/DAG (Phospholipase C)** pathway, not cAMP. * **Prolactin:** Prolactin (along with Growth Hormone and Insulin) utilizes the **JAK-STAT pathway** (Enzyme-linked receptor). It does not use cAMP as a second messenger. **3. Clinical Pearls & High-Yield Facts:** * **cAMP Pathway Mnemonic (FLAT ChAMP):** **F**SH, **L**H, **A**CTH, **T**SH, **C**alcitonin, **h**CG, **A**DH (V2), **M**SH, **P**TH. * **IP3/DAG Mnemonic (GOAT):** **G**nRH, **O**xytocin, **A**ngiotensin II, **T**RH. * **ANP/NO:** Utilize **cyclic GMP (cGMP)**. * **Steroid/Thyroid Hormones:** These are lipid-soluble and act via **intracellular/nuclear receptors** to alter gene transcription directly.

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.

Question 1

Decreased plasma renin activity is seen in which of the following conditions?

Accepted Answer

Primary hyperaldosteronism

Answer

Bartter syndrome

Answer

Preeclampsia

Answer

Secondary aldosteronism

Question 2

Angiotensinogen is secreted by which organ?

Accepted Answer

Liver

Answer

Kidney

Answer

Lung

Answer

Brain

Question 3

All of the following hormones are secreted by the adrenal cortex EXCEPT:

Accepted Answer

Estriol

Answer

Cortisol

Answer

Corticosterone

Answer

Aldosterone

Question 4

Which of the following factors determines whether a patient develops acromegaly or gigantism?

Accepted Answer

Age at onset of the tumor

Answer

Sex

Answer

Amount of available calcium

Answer

Degree of function of the tumor

Question 5

Parathyroid hormone is responsible for all actions except:

Accepted Answer

Increase in phosphorous absorption

Answer

Increase in Vitamin D absorption

Answer

Mobilization of calcium from bone

Answer

Increase in intestinal absorption of calcium

Question 6

Which hormone(s) utilize the cyclic adenosine monophosphate (cAMP) as a second messenger system?

Accepted Answer

Calcitonin

Answer

Angiotensin Converting Enzyme

Answer

Prolactin

Answer

All of the above

Question 7

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 8

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 9

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 10

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

Endocrinology — MCQs

Endocrinology — MCQs

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