The strengths of this review are as follows: a large number of references, covering long period of time, a thorough search of the current literature including studies written in languages other than English, data extraction by two independent reviewers, and the inclusion of studies that reported negative findings (i.e., studies denying a connection between prolactin/hyperprolactinaemia and endometriosis). The gene discussed is PRL; the disease is Increased circulating prolactin concentration.