Effects of Oral vs Transdermal Estrogen Therapy on Sexual Function in Early Postmenopause: Ancillary Study of the Kronos Early Estrogen Prevention Study (KEEPS).

Importance: Sexual dysfunction, an important determinant of women's health and quality of life, is commonly associated with declining estrogen levels around the menopausal transition.

Objective: To determine the effects of oral or transdermal estrogen therapy vs placebo on sexual function in postmenopausal women.

Design, Setting, and Participants: Ancillary study of the Kronos Early Estrogen Prevention Study (KEEPS), a 4-year prospective, randomized, double-blinded, placebo-controlled trial of menopausal hormone therapy in healthy, recently menopausal women. Of 727 KEEPS enrollees, 670 agreed to participate in this multicenter ancillary study. Women were 42 to 58 years old, within 36 months from last menstrual period. Data were collected from July 2005 through June 2008 and analyzed from July 2010 through June 2017.

Interventions: Women were randomized to either 0.45 mg/d oral conjugated equine estrogens (o-CEE), 50 µg/d transdermal 17β-estradiol (t-E2), or placebo. Participants also received 200 mg oral micronized progesterone (if randomized to o-CEE or t-E2) or placebo (if randomized to placebo estrogens) for 12 days each month.

Main Outcomes and Measures: Aspects of sexual function and experience (desire, arousal, lubrication, orgasm, satisfaction, and pain) were assessed using the Female Sexual Function Inventory (FSFI; range, 0-36 points; higher scores indicate better sexual function). Low sexual function (LSF) was defined as an FSFI overall score of less than 26.55. Distress related to low FSFI score (required for the diagnosis of sexual dysfunction) was not evaluated.

Results: The 670 participants had a mean (SD) age of 52.7 (2.6) years. The t-E2 treatment was associated with a significant yet moderate improvement in the FSFI overall score across all time points compared with placebo (average efficacy, 2.6; 95% CI, 1.11-4.10; adjusted P = .002). With o-CEE treatment, there was no significant difference in FSFI overall score compared with placebo (mean efficacy, 1.4; 95% CI, -0.1 to 2.8; adjusted P = .13). There was no difference in FSFI overall score between the t-E2 and o-CEE groups on average across 48 months (adjusted P = .22). In the individual domains of sexual function, t-E2 treatment was associated with a significant increase in mean lubrication (0.61; 95% CI, 0.25-0.97; P = .001) and decreased pain (0.67; 95% CI, 0.25-1.09; P = .002) compared with placebo. Overall, the proportion of women with LSF was significantly lower after t-E2 treatment compared with placebo (67%; 95% CI, 55%-77% vs 76%; 95% CI, 67%-83%; P = .04). For o-CEE there was no significant reduction in the odds of LSF.

Conclusions and Relevance: Treatment with t-E2 modestly improved sexual function in early postmenopausal women, but whether it relieved symptoms of distress is not known.

Trial Registration: clinicaltrials.gov Identifier: NCT00154180.