PRL and Increased circulating prolactin concentration: The authors of another study on the effects of danazol treatment for endometriosis also reported the absence of a significant difference in the basal PRL levels as well as its response to the TRH in patients with endometriosis before and after danazol treatment and concluded that hyperprolactinaemia should not be considered as a cause of infertility in endometriotic women [10].