1. Department of Internal Medicine and Center of Expertise on Gender Dysphoria; VU University Medical Center; Amsterdam the Netherlands
2. Department of Clinical Chemistry; VU University Medical Center; Amsterdam the Netherlands
3. Sexual Medicine and Andrology Unit, Department of Experimental, Clinical, and Biomedical Sciences; University of Florence; Florence Italy
4. Department of Endocrinology; Oslo University Hospital; Oslo Norway
5. Department of Endocrinology; Center for Sexology and Gender; Ghent University Hospital; Ghent Belgium