ORLANDO – Hormonal add-back therapy using combination norethindrone acetate and conjugated equine estrogens was effective and better than norethindrone acetate plus placebo for preserving bone health and improving quality of life in adolescents receiving treatment with gonadotropin-releasing hormone agonists (GnRH-A) for endometriosis in a randomized, double-blind, placebo-controlled study.

Of 51 adolescents aged 15-22 years who were initiating GnRH-A therapy for endometriosis, 25 were randomized to receive add-back therapy with 5 mg daily oral norethindrone acetate (NA) plus 0.625 mg oral daily conjugated equine estrogens (CEE), and 26 were randomized to receive NA plus placebo; 18 and 16, respectively, completed the study.

Those in the combination-therapy group experienced significant increases over 12 months in both total body bone mineral content (BMC) and bone mineral density (BMD), compared with those who received NA plus placebo. BMC increased by nearly 40 g/unit scanned in the combination-therapy group, compared with about 12 g in the NA plus placebo group, and BMD increased more than 0.01 g/cm², compared with no change in the NA plus placebo group, Dr. Amy D. DiVasta reported at the North American Society for Pediatric and Adolescent Gynecology annual meeting.

No losses of total hip or lumbar spine BMC or BMD occurred, said Dr. DiVasta of Boston Children’s Hospital.

Further, lean mass increased in the combination-therapy group at 12 months – by about 1.4 kg, compared with no change in the placebo group. No differences were seen between the groups in change in fat mass.

As for quality of life measures, overall physical health scores at baseline were significantly below the U.S. mean in both groups, and overall mental health scores were above the U.S. mean in both groups. Both groups improved over time on both measures; the increase in the Physical Component Summary scale scores on the SF-36 (Short Form 36 Health Survey) was significantly greater with combination-therapy group (increase from about 40 to 50 out of 100 ), compared with NA plus placebo (increase from about 40 to 45), but the increases on the Mental Component Summary scale scores were not statistically significant in either group, or between the groups.

The study subjects, who were treated for 12 months between 2008 and 2012, were at least 2 years post menarche at baseline and had a surgical diagnosis of endometriosis. The two treatment groups were similar with respect to baseline characteristics, including age, BMD Z score, and disease severity. No significant side effects were observed in either the combination or NA plus placebo group, Dr. DiVasta said, noting that laboratory tests included liver function tests and lipid levels.

Areal BMD, BMC, and body composition were measured by dual-energy X-ray absorptiometry (DXA) at baseline, 6 months, and 12 months. Anthropometrics, quality of life measures, and laboratory studies were conducted at 1, 3, 6, and 12 months.

GnRH-A are commonly utilized for endometriosis patients who fail primary therapy, such as NSAIDs or combined oral contraceptives, but long-term use is associated with deleterious effects on bone mineralization; adults have been shown to lose 5%-8% of BMD after 3-6 months of treatment, Dr. DiVasta noted.

Hormonal add-back therapy is a promising adjunct to counteract these effects and could be an important tool for protecting adolescents, who are at the greatest risk for the deleterious effects of GnRH-A therapy, she said.

In the current study, hormonal add-back did successfully protect bone health and improve quality of life for adolescents with endometriosis who were treated with 12 months of GnRH-A. Combination therapy with NA and CEE appears to be more effective for increasing total body BMC and BMD, lean mass, and physical health-related quality of life, as compared with NA monotherapy, she said.

The findings are limited by the inclusion of only skeletally mature young women, as the results may not be generalizable to growing girls. Also, DXA measures provide two-dimensional measures of bone mineral density, and do not yield information regarding skeletal strength or bone microarchitecture, she noted.

“Given the prevalence of endometriosis, our data suggest norethindrone plus estrogens to be a useful adjunctive therapy to prevent bone loss in these young women while they receive appropriate medical treatment for their underlying disease,” she concluded, noting that future work will explore the effects of add-back on the peripheral skeleton and bone strength.

This study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the McCarthy Family Foundation, Thrasher Research Fund, and Boston Children’s Hospital department of medicine. Medications were provided by Abbott, Duramed Pharmaceuticals, and Wyeth Pharmaceuticals. Dr. DiVasta reported having no relevant financial disclosures.

sworcester@frontlinemedcom.com

NASPAG: Hormonal add-back prevents GnRH-A–related bone loss in adolescents