It's an adaptogen which means it isn't a herb that mimics estrogen, it balances whatever is out of sync. It can raise progesterone if this is out of balance which is common in premenopause when estrogen becomes dominant and swings about, while progesterone slowly drops out of the picture
This is from Dr Marilyn Glenville website who is a nutritionalist in the UK.
Agnus Castus (Vitex agnus castus)
This herb is classed as an adaptogen as it has a balancing effect on your hormones. It works on the pituitary gland which is the gland that sends the message down to the ovary to release hormones. Agnus castus can help increase certain hormones if they are too low and decrease them if too high. This is particularly helpful in the perimenopause years because your hormones can be fluctuating widely and this herb helps to create a kind of stability. It is also the best herb to take if you are getting mood swings, anxiety and tension.
