It is the bioidentical hormone natural progesterone--not artificial progestins or estrogens, artificial or bioidentical--that protects the brain.

In premenopausal women and female animals, high estrogen is accompanied by high progesterone. And there is more and more evidence that it is the progesterone that protects the brain.

At menopause the body stops making progesterone (but not estrogen) almost altogether. If any progesterone is made after menopause it is not enough to register in medical blood tests.

These researchers were not relating the two hormones, and, if they had to focus on only one being brain protective were watching the wrong hormone.

Bioidentical progesterone even heals brain trauma. And there is evidence that HRT after menopause might even shrink brains and damage memory.

You can look up these studies on the web.

Results of this experiment are not unexpected at all, when you know the history of observations of progesterone in relation to the brain.

And unfortunately, these researchers are not alone in focusing on the wrong hormone to heal brain damage. There is a lot of hormone misinformation out there, based on faulty studies with wrong hypotheses, tunnel-visioned observations and hence wrong conclusions.