Researchers have found a new risk factorfor diabetic nephropathy—oral contraceptives(OCs). A strong association between therenin angiotensin system (RAS) and diabeticnephropathy led the researchers to explore apossible link with OC use. Initially the studyincluded 12 patients with diabetes who usedOCs and 10 patients without diabetes whoused oral OCs. The study also included 29patients with diabetes and 41 patients withoutthe disease, all of whom did not use OCs.Renal plasma flow (RPF) in response to captoprilwas used as an index of RAS activity.
The results of the study, reported in DiabetesCare (August 2005), showed thatpatients without diabetes who did not use OCshad a "minimal" increase in RPF, comparedwith a greater increase in patients without thedisease who used birth control. Furthermore,patients with diabetes who did not use OCshad a dramatically greater than anticipatedincrease. The vasodilator response, however,was most prevalent in the diabetic OC group.
The researchers went a step further tomeasure the impact of OC use in 114 womennewly diagnosed with type 1 diabetes. After 20years of follow-up, 18% of the OC groupdeveloped macroalbuminuria, compared with2% of nonusers of OCs. When the researchersadjusted for age at onset and bloodpressure, OC use remained a major predictorof development of the nephropathy.