Positioning gestrinone among the progestins: a narrative review of pharmacology, efficacy, safety, and tolerability

Introduction: Gestrinone is an androgenic progestin derived from 19-nortestosterone, in use for four decades in endometriosis and other estrogen-dependent conditions. It has largely disappeared from contemporary progestin taxonomies and is sometimes described as an anabolic-androgenic steroid. This review examines its pharmacology and the evidence for its use. Areas covered: Narrative review without a prespecified protocol, based on searches of PubMed, trial registries and regulatory sources, without date or language limits. It integrates chemistry and multireceptor pharmacology, pharmacokinetics, comparative efficacy against danazol, gonadotropin-releasing hormone (GnRH) agonists and other progestins, and safety, by indication, route and formulation. Expert opinion: Gestrinone was active in every controlled setting tested, and the direct comparisons against danazol and a GnRH agonist detected no difference in the principal pain outcomes, in trials too small to establish equivalence; no direct comparison with dienogest exists. Its hallmark is an androgenic-metabolic signature, and its androgenic effects are not consistently milder than those of danazol. Skeletal findings varied between studies and doses and do not establish long-term protection or the absence of a need for add-back therapy. Priorities are formulation-specific exposure data and contemporary comparisons.