Prevention of bone loss and hypoestrogenic symptoms by estrogen and interrupted progestogen add-back in long-term GnRH-agonist down-regulated patients with endometriosis and premenstrual syndrome

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Abstract
To examine the utility of a low-dose estrogen and pulsed progestogen hormone replacement therapy (HRT) regimen for add-back during long-term gonadotropin-releasing hormone-agonist (GnRH-agonist) therapy. A pilot clinical trial conducted at a tertiary referral, academic, reproductive sciences center. The study included 15 patients with endometriosis and 5 patients with severe premenstrual syndrome (PMS). Patients with endometriosis received leuprolide acetate depot 3.75 mg IM monthly until their symptoms had resolved (2–3 months), at which time HRT was initiated along with the GnRH-agonist. Patients with severe PMS received the same treatment with the addition of HRT after 1 month. The HRT regimen consisted of 1 mg oral micronized estradiol daily and 0.35 mg norethindrone daily for 2 days alternating with 2 days without norethindrone. The main outcome measure included bone density assessment in the lumbar spine and femoral neck by dual-energy x-ray absorptiometry at 6- to 12-month intervals. The mean follow-up duration ± SD while on GnRH-agonist treatment was 31.2 ± 17 months (for endometriosis patients) and 37.7 ± 8.4 months (for patients with severe PMS). Bone mineral density was stable after initiation of HRT for the entire follow-up period. No patient had return of pelvic pain or resumption of mood swings after HRT add-back. After the first 3 months of HRT, all women remained amenorrheic. Long-term GnRH-agonist down-regulation is safe and effective when combined with HRT add-back. Furthermore, on the basis of this small study, the low-dose pulsed progestogen, continuous estrogen HRT regimen seems to be safe for use as add-back therapy in terms of bone health.