A Study to Describe the Efficacy of Diphereline Following Conservative Surgery in Deep Infiltrating Endometriosis (DIE) Patients Over a Period of 24 Months

Inclusion Criteria: * Patients diagnosed with DIE and having received surgery treatment within one month before inclusion * Premenopausal women aged \>=18 years old. * Written ICF has been obtained prior to any study-related procedures * Patient for whom the treating physician already made the decision to treat by Diphereline. * Patient should be mentally and physically able to express her symptom complaints and answer questions. Exclusion Criteria: * Pregnancy or lactation. * Patients currently on treatment or who have been on therapy with a GnRHa in the last 6 months. * Premenopausal women who may reach menopause within the 3 years post randomisation. * Hypersensitivity to Triptorelin or one of the excipients of Triptorelin 3.75mg * Treatment with another research drug over the last 3 months before the study * Potentially unreliable patients, and those judged by the investigator to be unsuitable for the study.