Endocrinology — MCQs

Endocrinology Indian Medical PG Practice Questions and MCQs

Question 641: What is the best retrospective investigation to diagnose hyperglycemia of two weeks duration?

A. Ketone bodies
B. Glycosylated hemoglobin (Correct Answer)
C. Blood glucose
D. Chromosomal study

Explanation: The diagnosis of hyperglycemia over a specific retrospective period requires a marker that reflects average glucose levels over the lifespan of a specific protein. **1. Why Glycosylated Hemoglobin (HbA1c) is correct:** HbA1c is formed by the non-enzymatic attachment of glucose to hemoglobin (glycation) [1]. Since the average lifespan of a Red Blood Cell (RBC) is **120 days**, HbA1c typically reflects the glycemic status of the preceding **2–3 months** [1]. However, it is the most reliable retrospective marker available among the options. While **Fructosamine** (glycated albumin) is technically more sensitive for a shorter 2-week window (due to albumin's 20-day half-life), in the context of standard NEET-PG questions, HbA1c remains the gold-standard "retrospective" investigation for chronic hyperglycemia. **2. Why other options are incorrect:** * **Ketone bodies:** These indicate acute metabolic decompensation (e.g., Diabetic Ketoacidosis) and reflect current insulin deficiency, not a retrospective glycemic trend [2]. * **Blood glucose:** This provides a "snapshot" of the glucose level at the exact moment of sampling [3]. It cannot determine how long the hyperglycemia has persisted. * **Chromosomal study:** This is used for genetic disorders (e.g., Turner syndrome or Down syndrome) and has no role in the routine diagnosis or monitoring of hyperglycemia. **Clinical Pearls for NEET-PG:** * **Fructosamine:** Best for monitoring glucose over the last **1–3 weeks**. It is preferred in patients with hemolytic anemia or hemoglobinopathies where HbA1c is unreliable. * **HbA1c Targets:** Normal < 5.7%; Pre-diabetes 5.7–6.4%; Diabetes ≥ 6.5. * **False Low HbA1c:** Seen in conditions that decrease RBC lifespan (e.g., Hemolytic anemia, recent blood loss, pregnancy). * **False High HbA1c:** Seen in Vitamin B12/Folate deficiency or Splenectomy.

Question 642: A 35-year-old man presents with vomiting and confusion. On examination, Na+ is 120 mmol/L, K+ is 4.2 mmol/L, and uric acid is 2 mg/dL. The patient is not edematous. What is the most likely diagnosis?

A. Cerebral toxoplasmosis with SIADH (Correct Answer)
B. Hepatic failure
C. Severe dehydration
D. Congestive heart failure

Explanation: ### Explanation The clinical presentation points toward **Euvolemic Hyponatremia**, specifically the **Syndrome of Inappropriate Antidiuretic Hormone (SIADH)**. **1. Why Option A is Correct:** The patient has profound hyponatremia (120 mmol/L) without clinical signs of fluid overload (no edema) or dehydration, classifying it as euvolemic [1]. A key diagnostic clue here is the **low serum uric acid (2 mg/dL)**. In SIADH, the expansion of total body water leads to increased urinary excretion of uric acid (uricosuria), resulting in hypouricemia. Central Nervous System (CNS) disorders, such as **Cerebral Toxoplasmosis**, are well-known triggers for SIADH due to the unregulated release of ADH from the posterior pituitary [2]. **2. Why the Other Options are Incorrect:** * **Options B (Hepatic Failure) and D (CHF):** Both conditions cause **Hypervolemic Hyponatremia** [1]. Patients typically present with clinical signs of volume overload, such as edema, ascites, or raised JVP. Furthermore, uric acid levels are usually normal or elevated in these states, not low. * **Option C (Severe Dehydration):** This causes **Hypovolemic Hyponatremia** [1]. Clinical examination would show signs of fluid loss (dry mucous membranes, poor skin turgor, tachycardia). In dehydration, serum uric acid is typically **elevated** (hyperuricemia) due to increased proximal tubular reabsorption. **3. High-Yield Pearls for NEET-PG:** * **SIADH Triad:** Hyponatremia + Plasma Hypoosmolality + Concentrated Urine (Urine Osm > 100 mOsm/kg). * **Hypouricemia (<4 mg/dL)** is a highly specific marker for SIADH in the setting of hyponatremia. * **Management:** Fluid restriction is the first-line treatment [3]. For symptomatic/severe cases, use 3% hypertonic saline. * **Caution:** Rapid correction of chronic hyponatremia can lead to **Osmotic Demyelination Syndrome (Central Pontine Myelinolysis)** [3]. Limit correction to <8–10 mmol/L in 24 hours [3].

Question 643: Extraadrenal pheochromocytoma predominantly secretes which of the following substances?

A. Epinephrine
B. Norepinephrine (Correct Answer)
C. Dopamine
D. DOPA

Explanation: The correct answer is **Norepinephrine**. The biochemical profile of a catecholamine-secreting tumor depends on its enzymatic machinery. The conversion of norepinephrine to epinephrine requires the enzyme **Phenylethanolamine N-methyltransferase (PNMT)**. This enzyme is induced by high concentrations of cortisol, which is only available in the adrenal medulla via the intra-adrenal portal venous system [1]. Because **extra-adrenal pheochromocytomas** (also known as paragangliomas) lack access to these high local cortisol levels, they do not express PNMT. Consequently, they cannot convert norepinephrine to epinephrine and thus predominantly secrete **norepinephrine** [1]. **Analysis of Incorrect Options:** * **A. Epinephrine:** Predominantly secreted by adrenal pheochromocytomas because the adrenal medulla contains PNMT [2]. * **C & D. Dopamine/DOPA:** While some rare malignant or carotid body tumors may secrete dopamine, they are not the predominant secretion of typical extra-adrenal pheochromocytomas. Elevated dopamine is often a marker of a more primitive, undifferentiated, or malignant phenotype. **NEET-PG High-Yield Pearls:** * **Rule of 10s:** Traditionally, 10% of pheochromocytomas are extra-adrenal, 10% are bilateral, and 10% are malignant (though genetic studies now show up to 30-40% are hereditary). * **Organ of Zuckerkandl:** The most common site for extra-adrenal pheochromocytoma (usually located near the origin of the inferior mesenteric artery). * **Diagnosis:** The best initial screening test is **plasma free metanephrines** or 24-hour urinary fractionated metanephrines. * **Localization:** **¹²³I-MIBG scan** is highly specific for locating extra-adrenal tumors. * **Management:** Always start **Alpha-blockade** (e.g., Phenoxybenzamine) before Beta-blockade to avoid a hypertensive crisis.

Question 644: Which of the following drugs can cause lipodystrophy?

A. Atorvastatin
B. Probucol
C. Saquinavir (Correct Answer)
D. Gentamicin

Explanation: The correct answer is **Saquinavir**. **1. Why Saquinavir is correct:** Saquinavir is a **Protease Inhibitor (PI)** used in the treatment of HIV/AIDS. A well-documented adverse effect of the PI class is **HIV-associated Lipodystrophy Syndrome**. This condition is characterized by a metabolic triad: * **Lipoatrophy:** Loss of subcutaneous fat from the face and limbs. * **Lipohypertrophy:** Central fat accumulation (cushingoid appearance, "buffalo hump," and visceral obesity). * **Metabolic derangements:** Dyslipidemia and insulin resistance. The mechanism involves the inhibition of proteins involved in lipid metabolism (like CRABP-1) and adipocyte differentiation. **2. Why other options are incorrect:** * **Atorvastatin:** This is an HMG-CoA reductase inhibitor used to *treat* dyslipidemia [2]. Its primary side effects are myopathy and hepatotoxicity, not lipodystrophy [2], [3]. * **Probucol:** An older lipid-lowering agent that lowers LDL and HDL. It is associated with QT interval prolongation but does not cause lipodystrophy. * **Gentamicin:** An aminoglycoside antibiotic. Its hallmark toxicities are nephrotoxicity and ototoxicity (vestibulotoxicity). **3. High-Yield Clinical Pearls for NEET-PG:** * **HAART and Lipodystrophy:** While PIs (like Saquinavir, Ritonavir, Indinavir) are most notorious for fat redistribution, certain **NRTIs** (especially Stavudine and Zidovudine) are strongly linked to peripheral lipoatrophy due to mitochondrial toxicity [1]. * **Other causes of Lipodystrophy:** Repeated **Insulin injections** at the same site can cause localized lipodystrophy (prevented by rotating injection sites). * **Metabolic Syndrome:** Always monitor blood glucose and lipid profiles in patients on Protease Inhibitors.

Question 645: Weight loss is a feature of which of the following conditions?

A. Insulinoma
B. Hypothyroidism
C. Addison disease (Correct Answer)
D. Fatty liver

Explanation: **Explanation:** **Addison Disease (Primary Adrenal Insufficiency)** is characterized by the destruction of the adrenal cortex, leading to a deficiency of cortisol and aldosterone [1]. Weight loss is a hallmark feature (seen in >90% of patients) due to a combination of **anorexia** (loss of appetite), nausea, vomiting, and the catabolic state induced by chronic cortisol deficiency. Additionally, the loss of aldosterone leads to salt wasting and dehydration, further contributing to weight reduction. **Analysis of Incorrect Options:** * **Insulinoma:** This is an insulin-secreting tumor of the pancreas [3]. Excess insulin causes recurrent hypoglycemia, which stimulates hunger (polyphagia). Patients often eat frequently to avoid symptoms, typically leading to **weight gain** [3]. * **Hypothyroidism:** A deficiency in thyroid hormones (T3/T4) results in a decreased basal metabolic rate (BMR). This leads to **weight gain**, often accompanied by non-pitting edema (myxedema) and fluid retention. * **Fatty Liver (NAFLD):** Non-Alcoholic Fatty Liver Disease is strongly associated with metabolic syndrome, insulin resistance, and obesity. Therefore, it is typically a feature of **weight gain** rather than weight loss. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperpigmentation:** In primary adrenal insufficiency, high ACTH levels stimulate melanocytes (due to POMC cleavage), a feature *absent* in secondary adrenal insufficiency [2]. * **Electrolyte Triad:** Look for **Hyponatremia, Hyperkalemia, and Azotemia** in Addisonian crisis [1]. * **Screening Test:** The most specific initial test is the **ACTH Stimulation Test** (Cosyntropin test). * **Other causes of weight loss in Endocrinology:** Hyperthyroidism, Type 1 Diabetes Mellitus, and Pheochromocytoma.

Question 646: A 74-year-old woman has metastatic bone disease on x-ray. Which of the following mediators is least likely to be involved?

A. interleukin-6 (IL-6)
B. ectopic parathyroid hormone (PTH) (Correct Answer)
C. tumor necrosis factor (TNF)
D. interleukin-1 (IL-1)

Explanation: The primary mechanism behind metastatic bone disease (bone resorption) is the activation of **osteoclasts**. In malignancy, this occurs via local or systemic release of cytokines that stimulate the RANK/RANKL pathway [1]. **Why Ectopic PTH is the Correct Answer:** True **ectopic production of PTH** (the intact hormone) by non-parathyroid tumors is an **extremely rare** clinical entity. While many tumors cause hypercalcemia, they do so by secreting **Parathyroid Hormone-related Protein (PTHrP)**, not native PTH [2]. PTHrP mimics PTH action at the receptor level but is a distinct molecule [2]. Therefore, in the context of metastatic bone disease, ectopic PTH is the least likely mediator. **Analysis of Incorrect Options:** * **IL-1, IL-6, and TNF:** These are potent inflammatory cytokines often referred to as "Osteoclast Activating Factors" (OAFs) [1]. * **IL-1 (Osteoclast Activating Factor):** Directly stimulates osteoclast precursors [1]. * **IL-6:** Frequently secreted by myeloma cells and breast cancer metastases; it induces RANKL expression. * **TNF (Tumor Necrosis Factor):** Synergizes with RANKL to enhance bone resorption and is a key mediator in local bone destruction [1]. **NEET-PG High-Yield Pearls:** 1. **Humoral Hypercalcemia of Malignancy (HHM):** Most commonly caused by **PTHrP** (seen in Squamous cell CA of lung, renal cell CA) [1]. 2. **Local Osteolytic Hypercalcemia:** Driven by **IL-1, TNF-alpha, and IL-6** (seen in Multiple Myeloma and Breast Cancer). 3. **Lab Findings in HHM:** High Calcium, **Low PTH** (suppressed by high Ca2+), and High PTHrP [2]. 4. **1,25-dihydroxyvitamin D:** The mediator of hypercalcemia in **Lymphomas** (due to increased 1-alpha-hydroxylase activity).

Question 647: Which is the most common complication in type 2 diabetes mellitus?

A. Neuropathy (Correct Answer)
B. Nephropathy
C. Retinopathy
D. Coronary artery disease

Explanation: **Explanation:** **Neuropathy** is the most common chronic complication of Type 2 Diabetes Mellitus (T2DM) [1]. Epidemiological studies and clinical data indicate that approximately 50% of patients with long-standing diabetes will develop some form of neuropathy. The underlying pathophysiology involves a combination of metabolic factors (polyol pathway activation leading to sorbitol accumulation) and microvascular damage (ischemia of the *vasa nervorum*), resulting in nerve fiber loss [1]. Distal symmetric polyneuropathy is the most frequent clinical presentation [1]. **Analysis of Incorrect Options:** * **Nephropathy:** While it is a leading cause of end-stage renal disease (ESRD), it occurs in roughly 20–40% of patients, making it less frequent than neuropathy [2]. * **Retinopathy:** This is a highly specific microvascular complication, but its prevalence (approx. 25–35%) typically trails behind neuropathy in large-scale cross-sectional studies of T2DM [1]. * **Coronary Artery Disease (CAD):** Although CAD is the **most common cause of death** in diabetic patients, it is not the most common complication overall [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Neuropathy [1]. * **Most common cause of death:** Cardiovascular disease (specifically Myocardial Infarction) [2]. * **Earliest sign of Nephropathy:** Microalbuminuria (30–300 mg/day). * **Most common cause of blindness in T2DM:** Macular edema (though proliferative retinopathy is more severe). * **Screening:** In T2DM, screening for all microvascular complications should begin **at the time of diagnosis**, as the disease often remains asymptomatic for years prior to detection.

Question 648: Increased parathyroid hormone (PTH) is seen in all conditions except:

A. Primary and secondary hyperparathyroidism
B. Lithium-induced hyperparathyroidism
C. Thyrotoxicosis (Correct Answer)
D. Familial hypocalciuric hypercalcemia

Explanation: The core concept here is the physiological response of the parathyroid glands to serum calcium levels [1]. In **Thyrotoxicosis (Option C)**, high levels of thyroid hormones (T3/T4) stimulate osteoclast activity, leading to increased bone resorption. This releases calcium into the bloodstream, causing mild hypercalcemia. According to the negative feedback loop, elevated serum calcium suppresses the secretion of Parathyroid Hormone (PTH) [3]. Therefore, PTH levels are typically **low or suppressed** in thyrotoxicosis. **Analysis of Incorrect Options:** * **Primary Hyperparathyroidism:** Characterized by autonomous overproduction of PTH (usually due to an adenoma), leading to high PTH and high calcium [2]. * **Secondary Hyperparathyroidism:** A compensatory rise in PTH in response to chronic hypocalcemia (commonly seen in Chronic Kidney Disease or Vitamin D deficiency) [2]. * **Lithium-induced Hyperparathyroidism:** Lithium shifts the "set-point" of the calcium-sensing receptor (CaSR) in the parathyroid gland, requiring higher calcium levels to suppress PTH, thus resulting in elevated PTH. * **Familial Hypocalciuric Hypercalcemia (FHH):** Caused by an inactivating mutation in the CaSR. The body "perceives" normal calcium as low, leading to inappropriately high or high-normal PTH levels despite hypercalcemia. **NEET-PG High-Yield Pearls:** 1. **FHH vs. Primary Hyperparathyroidism:** Use the **Urinary Calcium/Creatinine Clearance Ratio**. In FHH, the ratio is <0.01 (low urine calcium); in Primary HPT, it is usually >0.02. 2. **Hungry Bone Syndrome:** Post-parathyroidectomy, a sudden drop in PTH leads to rapid bone uptake of calcium, causing severe hypocalcemia. 3. **Pseudohypoparathyroidism:** PTH is high, but there is end-organ resistance to its action (associated with Albright’s Hereditary Osteodystrophy).

Question 649: Which disease increases oral melanin pigmentation?

A. Addison's disease (Correct Answer)
B. Hyperthyroidism
C. Nephritis
D. All of the above

Explanation: **Explanation:** **1. Why Addison’s Disease is Correct:** Addison’s disease (Primary Adrenocortical Insufficiency) is characterized by the destruction of the adrenal cortex, leading to low levels of cortisol [1]. Due to the loss of negative feedback, the pituitary gland overproduces **Adrenocorticotropic Hormone (ACTH)**. ACTH is derived from a precursor molecule called **Pro-opiomelanocortin (POMC)**. When POMC is cleaved to produce ACTH, it also produces **Melanocyte-Stimulating Hormone (MSH)**. High levels of ACTH/MSH stimulate melanocytes in the skin and mucous membranes, leading to characteristic hyperpigmentation. This is most prominent in areas of friction, skin creases, and the **oral (buccal) mucosa**. **2. Why Other Options are Incorrect:** * **Hyperthyroidism:** While it can cause skin changes like pretibial myxedema or warm/moist skin, it does not involve the POMC pathway and therefore does not cause oral melanin pigmentation. * **Nephritis:** Kidney inflammation or chronic kidney disease may cause a "sallow" complexion (urochrome deposition) or generalized pruritus, but it is not a primary cause of oral mucosal melanosis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Primary vs. Secondary:** Hyperpigmentation occurs **only** in primary adrenal insufficiency. In secondary adrenal insufficiency (pituitary failure), ACTH levels are low, so the skin remains pale. * **Nelson’s Syndrome:** Rapid enlargement of a pituitary adenoma following bilateral adrenalectomy, leading to extreme hyperpigmentation due to massive ACTH release. * **Differential Diagnosis:** Other causes of oral pigmentation include Peutz-Jeghers Syndrome (perioral lentigines), Laugier-Hunziker syndrome, and heavy metal poisoning (e.g., Lead lines).

Question 650: Which of the following drugs does NOT cause nephrogenic diabetes insipidus?

A. Lithium
B. Demeclocycline
C. Acyclovir (Correct Answer)
D. Amphotericin B

Explanation: **Explanation:** Nephrogenic Diabetes Insipidus (NDI) occurs when the renal tubules are resistant to the action of Antidiuretic Hormone (ADH/Vasopressin), leading to the inability to concentrate urine. **Why Acyclovir is the correct answer:** Acyclovir is primarily associated with **obstructive acute kidney injury (crystal-induced nephropathy)**. When administered intravenously, especially without adequate hydration, acyclovir crystals precipitate in the renal tubules, causing direct damage and obstruction. It does not typically interfere with ADH signaling or the aquaporin-2 channels required to cause NDI. **Why the other options are incorrect:** * **Lithium (Option A):** The most common cause of drug-induced NDI. It enters the principal cells of the collecting duct via ENaC channels and inhibits glycogen synthase kinase-3β, leading to the downregulation of Aquaporin-2 channels. * **Demeclocycline (Option B):** A tetracycline derivative that inhibits the action of ADH. It is actually used therapeutically to treat SIADH because it reliably induces a state of NDI. * **Amphotericin B (Option D):** This antifungal is notorious for nephrotoxicity. It increases the permeability of the tubular membrane, causing a "washout" of the medullary concentration gradient and interfering with ADH responsiveness, leading to NDI and distal Renal Tubular Acidosis (Type 1). **High-Yield Clinical Pearls for NEET-PG:** * **Most common electrolyte cause of NDI:** Hypercalcemia and Hypokalemia. * **Drug of choice for Lithium-induced NDI:** Amiloride (it blocks ENaC channels, preventing Lithium entry into principal cells). * **Management of NDI:** Thiazide diuretics, NSAIDs (Indomethacin), and salt restriction. * **Distinguishing NDI from Central DI:** In NDI, there is **no increase** in urine osmolality following the administration of exogenous Desmopressin (Water Deprivation Test).

Practice by Chapter

Diabetes Mellitus

Practice Questions

Thyroid Disorders

Practice Questions

Adrenal Gland Disorders

Practice Questions

Pituitary Disorders

Practice Questions

Calcium and Bone Metabolism

Practice Questions

Reproductive Endocrinology

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Lipid Disorders

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Endocrine Hypertension

Practice Questions

Multiple Endocrine Neoplasia

Practice Questions

Obesity and Metabolic Syndrome

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Neuroendocrine Tumors

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Endocrine Emergencies

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