Pregnancy-associated plasma protein A: spotlight on kidney diseases.

Pregnancy-associated plasma protein A (PAPP-A) is a biomarker routinely used in screening for Down syndrome in the first trimester of pregnancy. It is also present in very small amounts in men and non-pregnant women. PAPP-A is a key regulator of local insulin-like growth factor (IGF) bioavailability - IGFs are essential for normal body size during fetal development, but they are associated with aging and age-related diseases. Measurement of circulating PAPP-A can provide valuable information not only in pregnant women (chromosomal anomalies and adverse pregnancy outcomes) but also in patients with coronary artery disease (contribution to diagnosis, prognostic value) and in patients with kidney diseases. PAPP-A is associated with renal function and proteinuria, is increased mainly in dialysis patients and decreases after kidney transplantation. It is an independent mortality predictor of hemodialysis patients and indicator of adverse outcome of transplanted patients. PAPP-A levels can be influenced by various chemicals and drugs, among them mainly heparin. Various assays for PAPP-A exist and the type of assay used in a study should be considered. This article reviews the data summarizing basic information about PAPP-A with a particular focus on the significance of PAPP-A in renal diseases.