Long-term use of postmenopausal estrogen treatment may impair kidney function

The harmful effect of high blood pressure on the blood vessels is one cause of kidney damage. Estrogen seems to protect against high blood pressure -- fewer premenopausal women have high blood pressure than men of the same age -- but after menopause, these benefits appear to diminish. Researchers from Tulane University in New Orleans studied a breed of rats that mimic the gender-specific blood pressure differences observed in humans to see if long-term hormone treatment negatively affects the kidneys.

The research team studied three groups of middle-aged rats without ovaries, which simulates the low estrogen environment of menopause. One group ("short-term") was given a short course of estrogen. A second group ("long-term") received a longer regimen of estrogen. The estrogen groups were compared to a control group that did not receive hormones.

Researchers found that after the hormone treatments, the long-term group had more damage to the tiny tubes that collect and carry urine than the short-term and control groups. The rate at which the kidneys filtered blood decreased, and creatinine levels and protein in the urine (markers of impaired kidney function) increased in the rats receiving long-term estrogen. The long-term group showed more kidney damage in each marker than the short-term or control groups.

The researchers explain that their "findings suggest that the duration of hormone therapy may be an important factor for renal health in aging postmenopausal women," especially in people with preexisting kidney damage.