Follow−up assessments will be performed during the treatment period 3, 6, 12, 18 and 24 months after the baseline visit. A final follow−up assessment will be conducted 6 months after stopping treatment. At each follow−up visit specific validated questionnaires on pain and endometriosis related health will be collected and symptoms of oestrogen deficiency will be noted. Physical examination, vital signs, bone density assessment and haematology and biochemistry analysis will be repeated at selected timepoints.