Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1163 page)

Decreased In

   Amenorrhea

   Threatened abortion (some patients)

   Fetal death

   Toxemia of pregnancy

   Gonadal agenesis
PROINSULIN

   Definition

   Enzymatic process forms insulin in pancreatic secretory granules of beta cells. Proinsulin level is normally ≤20% of total insulin. Proinsulin has low biologic activity (10% insulin potency) and is the major storage form of insulin. Proinsulin is included in the immunoassay of total insulin, and separation requires special technique.

   
Normal range:
2.0–2.6 pmol/L.

   Use

   Proinsulin: Insulin ratio is used as an indirect marker of beta cell function.

   Interpretation

   High proinsulin levels associated with benign or malignant beta cell tumors of the pancreas and endocrine pancreatic tumors associated with MEN-1.

   Elevated levels are positive risk factor for the development of NIDDM.