1. Departments of Endocrinology and Metabolism (M.L., H.P.S., C.E.M.H., M.J.S.), Laboratory of Endocrinology and Radiochemistry, Academic Medical Center, 1105AZ Amsterdam, The Netherlands
2. Departments of Medical Biochemistry (K.J.M.G., J.E.M.G., J.M.A.), Laboratory of Endocrinology and Radiochemistry, Academic Medical Center, 1105AZ Amsterdam, The Netherlands
3. Departments of Clinical Chemistry (M.T.A.), Laboratory of Endocrinology and Radiochemistry, Academic Medical Center, 1105AZ Amsterdam, The Netherlands