Estrona

For IN VITRO determination of serum or plasma ESTRONE levels. The origin of plasma estrogens in women has been precisely studied by refined isotopic dilution techniques. In normal women, most plasma estradiol is derived from the ovary, where theca cells secrete androstenedione, which is then converted to estrone and then to estradiol by the granulosa cells. Little estrone is indeed formed and secreted by the ovary : most originates from a peripheral conversion of estradiol and from the aromatisation of androstenedione, a catalytic reaction essentially carried out in adipose tissue. In premenopausal women, androstenedione is secreted by the ovary and the adrenals. In pregnant women, the fetal adrenal gland provides a significant contribution to androstenedione production. In menopausal women, estrone is the essential estrogen found in the circulation, resulting from the conversion of adrenal androstenedione. An increase in estrogen formation occurs with aging and in correlation with the amount of adipose tissue. The estrogenic effects of estrone in menopausal women can produce endometrial hyperplasia and bleeding but also maintains the bone mineral content. In premenopausal women, excessive estrone blood levels can result from the conversion of large amounts of androstenedione produced in micropolycystic ovary syndrome and ovarian tumors. In such women, high estrone blood levels can participate in a disturbance of the menstrual cycle. Estrone in the circulation is essentially bound to albumin. This is important in the interpretation of estrone-assay data. Indeed, and contrary to