The Metabolism of Estrogens in Normal Women After Pulse Injections of3H-Estradiol and3H-Estrone

Abstract

³H-estradiol was administered as a single pulse to 7 normal women between days 5–7 of their menstrual cycle. The disappearance from the blood of ³H as free estradiol in all 7 subjects could be best described as a function which was the sum of 3 exponentials. The mean (± se) initial volume of distribution (V¹) was 10.9 ±1.1 1. The mean metabolic clearance rate (MCR²) was 740 ± 50 1/day/m2, the mean blood production rate (P²_B) was 80 ± 11 μg/day. Estradiol contributed a mean 27 ± 7% to the production rate of estrone. ³H-estrone was administered as a single pulse to 5 normal women between days 5–7 of their cycle. In 3 women the disappearance from the blood of ³H as free estrone could be best described as a function which was the sum of 3 exponentials. In 2 women the disappearance of ³H as free estrone could be best described as a function which was the sum of 2 exponentials. For all 5 women the mean V¹ was 32.4 ± 6.5 1. The mean MCR¹ was 1120 1/day/m²; the mean (P¹_B) was 101 ± 13 μg/day. Estrone contributed a mean of 7 ± 2% to the production rate of estradiol. The appearance in the blood of ³H as estrone sulfate was studied in 5 women (2 after estradiol and 3 after estrone). In all 5 by 20–25 min ³H-estrone sulfate was present in higher concentration than either free estrogen and its concentration continued to rise slightly for a further 3–4 hr.