Relugolix in Monotherapy and Combined Therapy for the Treatment of Uterine Diseases and Its Effects on Bones: A Systematic Review

Background: Uterine fibroids (UFs) and endometriosis are gynecological conditions that significantly increase morbidity among women of reproductive age. Relugolix, a novel gonadotropin-releasing hormone receptor antagonist, is approved in combined therapy for the management of symptoms related to these disorders. However, its potential impact on bone mineral density (BMD) and osteoporosis risk should be considered when using a gonadotropin-releasing hormone (GnRH) antagonist. This systematic review aims to evaluate the effects of daily relugolix intake in monotherapy and combination therapy on BMD, ensuring safe long-term management. Methods: A systematic literature review was conducted following PRISMA 2020 guidelines. Searches were performed in PubMed, Medline, and the Cochrane Library. Relevant clinical guidelines from international societies were also reviewed. Studies assessing the impact of relugolix on BMD were selected, and data on treatment efficacy, adverse effects, and bone health outcomes were synthesized. Results: Relugolix monotherapy has been associated with significant BMD loss due to its potent estrogen-suppressing effect. To mitigate this, combination therapy with estradiol and norethisterone acetate has been developed. Although initial monotherapy before transitioning to combination therapy results in transient BMD reduction, clinical trials have demonstrated that relugolix combination therapy maintains BMD over two years while effectively reducing endometriosis- and UF-related symptoms. Conclusions: Relugolix combination therapy is an effective and well-tolerated treatment for UFs and endometriosis, minimizing the risk of hypoestrogenism-related bone loss while maintaining clinical benefits. Although monotherapy may lead to transient BMD reduction, combination therapy appears to stabilize bone health.