Fig. 10. Estrogen sources in postmenopausal women. A. The relatively small amounts of estradiol (E2) produced after the menopause primarily come from peripheral conversion of adrenal precursors androstenedione (A) and testosterone (T). B. The dominant postmenopausal estrogen is estrone (E1) which primarily comes from peripheral conversion of adrenal A. The ovary only makes a minor contribution to postmenopausal E1 from the sources identified. (Modified from Hammond CB, Soules M: Clinical significance of estrogen metabolism and physiology. Contemp OB/GYN 11:41, 1978.)