A study that appears in the journal Menopause tracked 400 postmenopausal women taking 20 mg. of black cohosh over a 52 week period.
This long-term study showed no findings of endometrial hyperplasia or endometrial thickeness. Serum estradiol levels remained in the postmenopausal range. There were no changes in breast density. There were no relevant cases of hepatotoxicity from increased liver enzymes levels.
Significant increases were found in osteocalcin activity, which reduces bone resorption (bone loss).