Further areas that remain to be clarified in the epidemiology of acromegaly include possible geographical variations and the impact of other factors (e.g. environmental, ethnic, sex, type of health care system, availability and access to health care resources), as well as data on early-onset and familial acromegaly and on mixed GH-prolactin secreting adenomas. This evidence concerns the gene GH1 and prolactin-producing pituitary gland adenoma.