CONTEXT: Most Turner syndrome (TS) girls need exogenous estrogen treatment to induce puberty and normal uterine growth. After puberty the optimal estrogen treatment protocol has not been determined.

OBJECTIVE: To compare two doses of oral 17ß-estradiol on uterine size.

DESIGN: A double-blind 5 years randomized controlled clinical trial.

SETTING: Ambulatory care.

PARTICIPANTS: 20 young TS women (19.2±2.5 years, range 16.0-24.9) participated. 16 patients completed the study. No patients withdrew due to adverse effects.

INTERVENTION: The lower-dose (LD) group took 2 mg 17ß-estradiol/day orally and placebo. The higher-dose (HD) group took 4 mg 17ß-estradiol/day orally.

RESULTS: Uterine size increased significantly more in the HD group compared to the LD group (P=0.038), with a gain in uterine volume within the first three years of treatment of 19.6 ml (95% CI = [4.0; 19.0]) in the HD group compared to 11.5 ml (95% CI = [11.2; 27.9]) in the LD group. The difference in three-year gain was 8.1 ml (95% CI = [0.7; 15.9]). At the last visit there were no significant differences in uterine volume between the groups.

CONCLUSION: High dose oral 17ß-estradiol induces a steeper increase in uterine volume within the first years of treatment compared to the lower dose. However, the uterine growth potential seems to be the same in most young TS women making the duration of treatment equally significant as estrogen dose, although a few TS did not experience sufficient uterine growth on 2 mg of estradiol.