Pharmacokinetics and Pharmacodynamics of Oral and Transdermal 17β Estradiol in Girls with Turner Syndrome

Abstract

The type, dose, and route of 17β-estradiol (E(2)) used to feminize girls with Turner syndrome (TS) is not well established. The objective of the study was to characterize pharmacokinetics and pharmacodynamics of oral vs. transdermal E(2). The study was conducted at a clinical research center. Ten girls with TS, mean age 17.7 ± 0.4 (se) yr and 20 normally menstruating controls (aged 16.8 ± 0.4 yr) participated in the study. TS subjects were randomized 2 wk each to: low-dose daily oral (0.5 mg) and biweekly transdermal E(2) (0.0375 mg) with 2 wk washout in between or high-dose oral (2.0 mg) and transdermal (0.075 mg), studied for 24 h each. Tandem mass spectrometry E(2) and estrone (E(1)) assays and a recombinant cell bioassay were used. Controls consisted of the following: E(2), 96 ± 11 pg/ml (se), E(1), 70 ± 7 (mean follicular/luteal). TS consisted of the following: E(2), average concentration on low-dose oral, 18 ± 2.1 pg/ml, low-dose transdermal, 38 ± 13, high-dose oral, 46 ± 15, high-dose transdermal, 114 ± 31 pg/ml. E(1) concentrations were much higher on oral E(2) (low or high dose) than transdermal in TS and higher than controls. Bioestrogen was closest to normal in the high-dose transdermal group. LH and FSH decreased more in transdermal than oral low-dose routes and similarly in the high-dose oral and transdermal groups. IGF-I concentrations were variable (P = NS) among groups, and low-density lipoprotein/high-density lipoprotein cholesterol responses were variable. Transdermal E(2) results in E(2), E(1), and bioestrogen concentrations closer to normal and achieves greater suppression of LH/FSH in lower doses compared with normal. Whether the long-term metabolic effects of estrogen differ using the same form of E(2), depending on route, awaits further study in TS.