Estrone excretion

Reifenstein and Dempseyl9 using Talbot s colorimetric method found the urinary "estrone" to vary from 10 to 39 ig. per day in 5 normal women and from 27 to 40 ig. per day for 5 normal men. Attention was not paid to the question of whether the observed differences were primarily inter-individual. In another study20 involving 3 men and 2 women, Pincus found about a 12-fold variation between the two women. One woman excreted over a period of several days estradiol + estrone + estriol to the extent of 155.2 ig. per day for the other woman and the 3 men, the corresponding values were respectively 13.4 ig., 12.4 ig., 7.6 ig. and 16.8 ig. 

The natural hormones are unsuitable for oral application because they are subject to presystemic hepatic elimination. Estradiol is converted via estrone to estriol by conjugation, all three can be rendered water soluble and amenable to renal excretion. The major metabolite of progesterone is pregnandiol, which is also conjugated and eliminated renally. 

Pharmacokinetics Readily absorbed from the gastrointestinal (Gl) tract. Widely distributed. Protein binding 50%-80%. Rapidly metabolized in liver and Gl tract to estrone sulfate and conjugated and unconjugated metabolites. Excreted in urine and bile. Half-life Unknown. 

Natural estrogens are inactive orally due to rapid metabolism in liver. Synthetic estrogens are well absorbed after oral administration as well as by transdermal application. Estradiol is metabolized to estrone and estriol. All these are conjugated and excreted in urine and bile. Synthetic... 

Approx 30 2-hydroxylation (CYP3A4) and sulphate and glucuronide conjugation and up to 30% is excreted unoxidized. Excretion is 60% renal and 40% in faeces. High first pass metabolism Estrone (small amounts)... 

The primary estrogen in premenopausal women is 17-P-estradiol (E2), which is synthesized by developing ovarian follicles. Estradiol is oxidized to estrone (El) and then to estriol (E3). Estrone is also produced in peripheral tissues by aromatization of androstenedione, an androgen precursor that is produced by both the ovaries and the adrenal glands after the menopause, estrone produced in this way becomes the predominant estrogen. All of the estrogens are sulfated and glucuronidated before excretion. 

DIO. Diczfalusy, E., Tillinger, K.-G., and Westman, A., Studies on estrogen metabolism in newborn boys. 1. Excretion of estrone, estradiol-17/8 and estriol during the first few days of life. Acta Endocrinol. 26, 303-312 (1957). 

Importantly, these hormones including estradiol dehydrogenase are chiefly metabolized in the liver and mostly get excreted as water-soluble glucuronide and sulphate conjugates. Estrone is regarded as a less active (1/12) metabolite of estradiol. 

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