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 2 doses of oral 17ß-estradiol on uterine size.

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

SETTING: Ambulatory care.

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

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

MAIN OUTCOME MEASURE(S): Uterine volume evaluated by transabdominal ultrasound yearly.

RESULTS: Uterine size increased significantly more in the HD group compared with the LD group (P = 0.038), with a gain in uterine volume within the first 3 years of treatment of 19.6 mL (95% confidence interval [CI] = 4.0-19.0) in the HD group compared with 11.5 mL (95% CI = 11.2-27.9) in the LD group. The difference in 3-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: HD oral 17ß-estradiol induces a steeper increase in uterine volume within the first years of treatment compared with the LD. 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 women did not experience sufficient uterine growth on 2 mg of estradiol.

CLINICALTRIALS.GOV: NCT00134745Abbreviations: BMI, body mass index; BSA, body surface area; DHEAS, dihydroepiandrosteronesulfate; HD, higher dose; HRT, hormone replacement therapy; LD, lower dose; TS, Turner syndrome; US, ultrasound.