The estradiol is primarily secreted from the ovaries

The estradiol is primarily secreted from the ovaries. It is the most abundant circulating form of oestrogen in the premenopausal female.

The estrone is synthesized from DHEA in adipose tissue stroma. It is the most abundant circulating form of oestrogen in the postmenopausal female.

In pregnancy, Placenta uses DHEA and it’s 16 Alpha hydroxyl derivative to form large amounts of estrone & estriol.

Estriol is the predominant form of oestrogen in pregnancy.