Hormone replacement therapy may be good for a woman's kidneys, a preliminary study suggests.

"The risks and benefits of hormone replacement therapy in postmenopausal women are still an area of active debate, and the effect of hormone replacement therapy on the kidney has shown variable results," said study author Dr. Andrea Kattah of the Mayo Clinic in Minnesota.

Her study compared nearly 700 older women taking hormone replacements with more than 1,500 who were not.

Rates of two indicators of kidney disease -- microalbuminuria and decreased estimated glomerular filtration rate -- were much lower in the women taking hormone replacements, the study found.

Microalbuminuria occurs with higher-than-normal levels of a protein called albumin in urine that could be a sign of kidney damage.

After they adjusted for known kidney and heart disease risk factors, the researchers found that hormone replacement was still strongly associated with lower rates of microalbuminuria.

But only an association and not a cause-and-effect link was seen in the study.

The study will be presented Nov. 5 at an American Society of Nephrology meeting in San Diego. Data and conclusions should be considered preliminary until the results are published in a peer-reviewed medical journal.

"Clarifying the role of hormones on kidney function may have implications for explaining gender differences in chronic kidney disease, counseling women on the use of hormone replacement therapy, and future therapeutic targets for patients with chronic kidney disease," Kattah said in a society news release.

Because of potentially dangerous side effects, hormone replacement therapy should only be taken for as long as necessary at the lowest effective dose, doctors say. It is typically prescribed for managing symptoms of menopause.