The Women's Health Initiative (WHI) study was flawed due to its use of oral conjugated equine estrogens and synthetic progestins, rather than actual progesterone, and its focus solely on women.

“and also you're replacing just one hormone with lots of Verona's are changing it didn't look like a good study to me well especially at the time and I try to be temper my criticism for that study by trying to have some empathy for the fact that the investigators were dealing with what the treatment protocols were at the time but to use oral estrogen that's you know conjugated aquaian to use synthetic progestin and not even actual progesterone and there you could come up with a list of 18 things that in retrospect are so obvious why that study was a failure”