Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (942 page)

   Bone disease or patients with increased bone growth (children and adolescents); therefore, useful in distinguishing bone disease from liver disease as a cause of increased serum ALP

   Renal failure

   Strenuous exercise

   Limitations

   Half-life is about 7–10 days; in alcohol-associated liver injury, the half-life is increased to as much as 28 days, suggesting impaired clearance.

   Day-to-day variations are 10–15%; approximately double in African Americans.

   There is a 25–50% increase with higher body mass index.

   Values are 25% lower during early pregnancy.

GASTRIN

   Definition

   Gastrin is a hormone secreted by the G-cells of the antrum of the stomach and the pancreatic islet of Langerhans. Its secretion is stimulated by alkalinity, by distention of the stomach by the antrum, by vagal stimulation, and by the presence of peptides, amino acids, alcohol, or calcium in the stomach. Its secretion is inhibited by gastric acidity via negative feedback system.

   Principal forms of gastrin in the blood are G-34 (big gastrin), G-17 (little gastrin), and G-14 (mini gastrin). Each of these circulates in nonsulfated and sulfated forms.

   The gastric stimulation test after calcium infusion (15 mg of Ca/kg in 500 mL normal saline over 4 hours) is useful in patients with marked elevation of gastrin levels. This test should be reserved for patients with a negative secretin test, gastric acid hypersecretion, and a strong suspicion of Z-E syndrome.

   
Normal range: