Endocrinology Practice Questions

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

Glycosylated hemoglobin. 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.

Q: 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?

Cerebral toxoplasmosis with SIADH. ### 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].

Q: Extraadrenal pheochromocytoma predominantly secretes which of the following substances?

Norepinephrine. 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.

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

Neuropathy. **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.

Q: Which disease increases oral melanin pigmentation?

Addison's disease. **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).

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

Acyclovir. **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).

Q: A 69-year-old female presents with recent onset of mild back pain, kyphosis, and a compression fracture of a vertebral body in the dorsal spine. Spondylotic changes and mildly reduced bone density are noted on X-ray. Laboratory investigations including serum calcium, phosphorus, alkaline phosphatase, ESR, and parathyroid hormone levels are all within normal limits. What is the most likely cause of this woman's bone changes?

Osteoporosis. ### Explanation The clinical presentation of an elderly female with kyphosis, a vertebral compression fracture, and reduced bone density on X-ray, coupled with **normal biochemical markers**, is classic for **Osteoporosis**. #### Why Osteoporosis is Correct Osteoporosis is characterized by a reduction in total bone mass (both mineral and matrix are decreased), but the remaining bone is chemically normal. Because the process is a quantitative rather than qualitative defect, serum levels of **Calcium, Phosphorus, and Alkaline Phosphatase (ALP) remain normal**. It is the most common cause of pathological vertebral fractures in postmenopausal women. #### Why Other Options are Incorrect * **Myeloma:** While it causes compression fractures in the elderly, it is usually associated with an **elevated ESR**, anemia, and often hypercalcemia or abnormal protein electrophoresis. * **Osteomalacia:** This involves a defect in bone mineralization. It typically presents with **low/normal serum calcium and phosphorus** and **elevated ALP**. Radiologically, it shows "fuzzy" trabeculae and Looser’s zones rather than simple compression fractures. * **Paget’s Disease:** This is characterized by excessive bone remodeling. The hallmark biochemical finding is a **markedly elevated ALP** with normal calcium and phosphorus. X-rays would show cortical thickening and trabecular coarsening (e.g., "Picture frame" vertebra), not just reduced density. #### NEET-PG Clinical Pearls * **Gold Standard Diagnosis:** DEXA Scan (T-score ≤ -2.5). * **Biochemical Profile:** In uncomplicated osteoporosis, Ca, PO₄, and ALP are always **Normal**. * **Most Common Site of Fracture:** Vertebral body (compression fracture), followed by the neck of the femur and Colles’ fracture. * **Radiological Sign:** "Codfish vertebra" (biconcave appearance) due to disk expansion into weakened vertebral bodies.

Q: A 40-year-old female presents with fever, fatigue, and diffuse painful swelling in the midline of the neck. FNAC revealed epithelioid cells and giant cells. What is the most likely diagnosis?

Subacute thyroiditis. The clinical presentation of a **painful, diffuse midline neck swelling** (thyroid) associated with systemic symptoms like **fever and fatigue** is classic for **Subacute Thyroiditis (De Quervain’s Thyroiditis)**. [2] **Why Subacute Thyroiditis is correct:** This condition is typically post-viral. The hallmark histopathological finding on Fine Needle Aspiration Cytology (FNAC) is the presence of **multinucleated giant cells** and **epithelioid cells** forming "pseudo-tubercles" surrounding collapsed follicles. [2] Clinically, patients often present with a tender thyroid and an elevated ESR. **Why the other options are incorrect:** * **Acute Thyroiditis:** This is a bacterial infection (usually *S. aureus*). While it presents with fever and pain, FNAC would show **neutrophils and abscess formation**, not giant cells or epithelioid cells. * **Tubercular Lymphadenitis:** While this shows epithelioid cells and giant cells (caseating granulomas), the swelling is typically located in the **lateral neck (cervical lymph nodes)**, not as a diffuse midline thyroid swelling. * **Hashimoto’s Thyroiditis:** This is usually a **painless** goiter. [3] FNAC characteristically shows a dense **lymphocytic infiltrate** and **Hurthle cells** (Askanazy cells), not the giant cells seen in the subacute variety. [3][4] **NEET-PG High-Yield Pearls:** * **De Quervain’s** is the most common cause of a **painful** thyroid. [2] * **Lab findings:** High ESR, low TSH (initially), and characteristically **low radioactive iodine uptake (RAIU)** due to follicular destruction. [1] * **Treatment:** Primarily symptomatic with NSAIDs; steroids are used for severe pain. [2] It is usually self-limiting. [1]

Question 1

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

Accepted Answer

Glycosylated hemoglobin

Answer

Ketone bodies

Answer

Blood glucose

Answer

Chromosomal study

Question 2

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?

Accepted Answer

Cerebral toxoplasmosis with SIADH

Answer

Hepatic failure

Answer

Severe dehydration

Answer

Congestive heart failure

Question 3

Extraadrenal pheochromocytoma predominantly secretes which of the following substances?

Accepted Answer

Norepinephrine

Answer

Epinephrine

Answer

Dopamine

Answer

DOPA

Question 4

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

Accepted Answer

Neuropathy

Answer

Nephropathy

Answer

Retinopathy

Answer

Coronary artery disease

Question 5

Which disease increases oral melanin pigmentation?

Accepted Answer

Addison's disease

Answer

Hyperthyroidism

Answer

Nephritis

Answer

All of the above

Question 6

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

Accepted Answer

Acyclovir

Answer

Lithium

Answer

Demeclocycline

Answer

Amphotericin B

Question 7

A 69-year-old female presents with recent onset of mild back pain, kyphosis, and a compression fracture of a vertebral body in the dorsal spine. Spondylotic changes and mildly reduced bone density are noted on X-ray. Laboratory investigations including serum calcium, phosphorus, alkaline phosphatase, ESR, and parathyroid hormone levels are all within normal limits. What is the most likely cause of this woman's bone changes?

Accepted Answer

Osteoporosis

Answer

Myeloma

Answer

Osteomalacia

Answer

Paget's disease

Question 8

A 35-year-old emaciated male with a history of disseminated tuberculosis presents with the following features: BP = 85/60 mmHg, low volume pulse of 100 BPM, diffuse hyperpigmentation involving hand creases, serum Na+ = 120 meq/L, and serum K+ = 6.6 meq/L. What is your most immediate response?

Accepted Answer

Suspect adrenocortical insufficiency and start IV steroids.

Answer

Suspect secondary hyperaldosteronism and start IV steroids.

Answer

Suspect gram-negative sepsis and start IV antibiotics.

Answer

Suspect massive pulmonary thromboembolism and start IV Heparin.

Question 9

A 40-year-old female presents with fever, fatigue, and diffuse painful swelling in the midline of the neck. FNAC revealed epithelioid cells and giant cells. What is the most likely diagnosis?

Accepted Answer

Subacute thyroiditis

Answer

Acute thyroiditis

Answer

Tubercular lymphadenitis

Answer

Hashimoto's thyroiditis

Question 10

A patient presented with the following serum parameters: Normal serum ALP, normal PTH level, and increased Ca+ and PO4. What is the most likely cause?

Accepted Answer

Vitamin D intoxication

Answer

Hyperparathyroidism

Answer

Osteoporosis

Answer

Osteomalacia

Endocrinology — MCQs

Endocrinology — MCQs

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