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BI11.1-2 | Organ Function tests and Hormones — Gate Quiz
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In acute viral hepatitis, which enzymes are most markedly elevated reflecting hepatocellular damage?
Correct! ALT and AST are released from damaged hepatocytes. In acute hepatitis these can rise 10-100 times normal. ALT is more liver-specific than AST.
Hepatocellular damage = elevated ALT/AST. Cholestasis = elevated ALP, GGT, direct bilirubin. AST:ALT ratio greater than 2 suggests alcoholic hepatitis.
Incorrect. ALT and AST are the primary markers of hepatocellular damage.
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In haemolytic jaundice, which type of bilirubin is predominantly elevated?
Correct! Haemolytic jaundice causes excess unconjugated bilirubin from excess RBC destruction. Unconjugated bilirubin cannot be excreted in urine — acholuric jaundice.
Prehepatic (haemolytic): elevated unconjugated bilirubin, no dark urine. Posthepatic (obstructive): elevated conjugated bilirubin, dark urine, pale stools. Neonatal jaundice: unconjugated from immature glucuronyl transferase.
Incorrect. Haemolytic jaundice causes elevated unconjugated bilirubin.
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Creatinine is a more reliable GFR marker than urea because:
Correct! Creatinine is produced at a constant rate from muscle creatine phosphate, freely filtered, and minimally secreted or reabsorbed, making it a reliable GFR marker.
Urea is affected by protein intake, GI bleeding, and tubular reabsorption. Creatinine is more stable. Normal GFR approximately 90-120 mL/min. CKD-EPI equation estimates GFR from creatinine, age, sex.
Incorrect. Constant production and minimal tubular handling make creatinine more reliable than urea.
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Thyroid hormones T3 and T4 are synthesized from which amino acid and require which element?
Correct! Thyroid hormones are synthesized from tyrosine residues in thyroglobulin with iodination of the phenol ring. T4 has 4 iodine atoms; T3 has 3.
Thyroid hormone synthesis: iodide uptake (Na+/I- symporter), oxidation to I2 (thyroid peroxidase TPO), organification of tyrosine in thyroglobulin, coupling of MIT + DIT. TPO is inhibited by propylthiouracil and methimazole.
Incorrect. Thyroid hormones are synthesized from tyrosine with iodine.
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The insulin receptor has intrinsic tyrosine kinase activity. It belongs to which receptor class?
Correct! The insulin receptor is a receptor tyrosine kinase. Upon insulin binding, the beta subunit autophosphorylates, initiating the PI3K/Akt signalling cascade leading to GLUT4 translocation.
Insulin signalling: insulin binds alpha subunits, beta subunit tyrosine kinase autophosphorylates, phosphorylates IRS-1/2, activates PI3K, generates PIP3, activates Akt/PKB: GLUT4 translocation, glycogen synthase activation.
Incorrect. The insulin receptor is a receptor tyrosine kinase.
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A 60-year-old man presents 6 hours after chest pain onset. Which biochemical marker is most sensitive and specific for MI at this time?
Correct! Troponin I and T are the most sensitive and specific markers for MI. They rise within 4-6 hours, peak at 24-48 hours, and remain elevated for 7-14 days.
Cardiac marker timeline: Myoglobin rises 1-3 hours (earliest, non-specific). CK-MB rises 4-6 hours, peaks 24 hours, normalises 48-72 hours. Troponin I/T rises 4-6 hours, elevated 7-14 days (allows late diagnosis).
Incorrect. Troponin I and T are the gold standard for MI diagnosis.
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Steroid hormones (cortisol, aldosterone, testosterone, oestrogen) primarily act by:
Correct! Steroid hormones are lipid-soluble, diffuse through the plasma membrane, bind intracellular receptors. The hormone-receptor complex acts as a transcription factor binding hormone response elements (HREs) in DNA.
Lipid-soluble hormones (intracellular receptors): steroids, thyroid hormones (T3/T4), Vitamin D, retinoic acid. Water-soluble hormones use surface receptors and second messengers.
Incorrect. Steroid hormones bind intracellular receptors that regulate transcription.
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In cirrhosis, serum albumin is low primarily because:
Correct! The liver is the sole site of albumin synthesis. In cirrhosis, reduced functional hepatocyte mass impairs albumin production. Low albumin reduces plasma oncotic pressure, contributing to ascites and oedema.
Serum albumin: normal 3.5-5.0 g/dL. Half-life approximately 20 days (reflects chronic synthetic function). Child-Pugh score uses albumin. Low albumin affects drug binding and calcium interpretation.
Incorrect. Albumin is synthesized exclusively in the liver, so hepatic damage reduces production.
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An OGTT shows fasting plasma glucose 105 mg/dL and 2-hour post-load glucose 170 mg/dL. According to ADA criteria, this patient has:
Correct! ADA prediabetes: Impaired Fasting Glucose (IFG) = fasting 100-125 mg/dL. Impaired Glucose Tolerance (IGT) = 2-hour OGTT 140-199 mg/dL. This patient has both = prediabetes.
ADA criteria: Normal: fasting less than 100, 2-hour less than 140. Prediabetes: fasting 100-125 or 2-hour 140-199 or HbA1c 5.7-6.4%. Diabetes: fasting 126 or more, or 2-hour 200 or more, or HbA1c 6.5% or more.
Incorrect. Fasting 100-125 mg/dL and 2-hour OGTT 140-199 mg/dL = prediabetes.
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In obstructive jaundice, elevated serum ALP is due to:
Correct! In cholestasis, bile acids accumulate and stimulate bile duct epithelium to synthesize ALP. ALP then leaks into the blood via tight junctions.
ALP isoforms: Liver (biliary epithelium), Bone (osteoblasts), Placenta, Intestine. To differentiate liver vs bone ALP: measure GGT (elevated in liver disease, normal in bone). ALP elevated in: cholestasis, bone metastases, Paget disease, hyperparathyroidism, normal pregnancy.
Incorrect. In cholestasis, bile acids stimulate biliary ALP synthesis, which regurgitates into blood.
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