Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1025 page)

   
Normal ranges:

   Child, prepubertal: 334–642 ng/mL

   Child, pubertal: 245–737 ng/mL

   Adult: 288–736 ng/mL

   GH deficiency: 51–299 ng/mL

   Use

   IGF-II is an adjunct to IGF-I in the clinical evaluation of GH-related disorders.

   Interpretation

Increased In

   Hypoglycemia associated with non–islet cell tumors

   Hepatoma

   Wilms tumor

Decreased In

   GH deficiency

INSULIN–TO–C-PEPTIDE RATIO

   Definition

   Insulin and C-peptide are secreted into portal vein in equimolar amounts, but serum ratio = 1:5 to 1:15 due to removal of approximately 50% of insulin from blood during initial passage through the liver. C-peptide half-life = approximately 30 minutes.