Researchers have found a new risk factor for diabetic nephropathyoral contraceptives (OCs). A strong association between the renin angiotensin system (RAS) and diabetic nephropathy led the researchers to explore a possible link with OC use. Initially the study included 12 patients with diabetes who used OCs and 10 patients without diabetes who used oral OCs. The study also included 29 patients with diabetes and 41 patients without the disease, all of whom did not use OCs. Renal plasma flow (RPF) in response to captopril was used as an index of RAS activity.
The results of the study, reported in Diabetes Care (August 2005), showed that patients without diabetes who did not use OCs had a "minimal" increase in RPF, compared with a greater increase in patients without the disease who used birth control. Furthermore, patients with diabetes who did not use OCs had a dramatically greater than anticipated increase. The vasodilator response, however, was most prevalent in the diabetic OC group.
The researchers went a step further to measure the impact of OC use in 114 women newly diagnosed with type 1 diabetes. After 20 years of follow-up, 18% of the OC group developed macroalbuminuria, compared with 2% of nonusers of OCs. When the researchers adjusted for age at onset and blood pressure, OC use remained a major predictor of development of the nephropathy.