1. Division of Endocrinology and Metabolism; Department of Internal Medicine; Medical University of Graz; Graz Austria
2. University Women's Hospital; Heidelberg Germany
3. Department of Epidemiology and Biostatistics and EMGO Institute for Health and Care Research; VU University Medical Center; Amsterdam The Netherlands
4. Das Kinderwunsch Institut; Dobl Austria
5. Department of Clinical Chemistry; VU University Medical Center; Amsterdam The Netherlands