THURSDAY, Nov. 29, 2007 (HealthDay News) -- There's no evidence that progesterone -- which is often given with estrogen in hormone replacement therapy -- offers women any protection against Alzheimer's disease, U.S. researchers say.
They conducted tests on female mice genetically engineered to develop an Alzheimer's-like disease to come to this conclusion.
Treatment with estrogen blocked the Alzheimer's-like symptoms in the mice, while treatment with progesterone did not. In fact, when the mice were given both hormones, progesterone appeared to block estrogen's main benefit -- preventing the buildup of beta amyloid protein in the brain, a key factor in Alzheimer's.
The researchers, led by gerontologist Christian Pike of the University of Southern California, did find that progesterone seemed to inhibit tau hyperphosphorylation, another chemical process implicated in Alzheimer's.
The study appears in this week's issue of the Journal of Neuroscience.
Previous research suggested that estrogen offers women some protection against Alzheimer's disease. The authors of this new study wanted to determine if the same might be true of progesterone.
The findings may provide guidance for the design of human trials examining hormone therapy and Alzheimer's, Pike said. Future studies may need to focus on both the dosage and formulations of progestins (synthetic versions of progesterone given to humans), as well as the starting age for hormone therapy, he noted.
The U.S. National Institute on Aging discusses whether Alzheimer's can be prevented.