Many studies of chronic renal disease have reported that men have a more rapid progression of renal insufficiency. However, other studies have found no differences between the sexes, and the true effect of sex on chronic renal disease remains a topic of controversy. There is evidence that women with non-diabetic renal diseases experience a slower progression, but in diabetic renal disease, the effect of gender is not yet established. Sex hormones may mediate the effects of gender on chronic renal disease, through alterations in the renin--angiotensin system, reduction in mesangial collagen synthesis, the modification of collagen degradation, and upregulation of nitric oxide synthesis.