1. Departments of Endocrinology and Metabolism (M.R.S., H.P.S., E.F., M.J.S.), Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam, The Netherlands
2. Department of Medical Biochemistry (J.E.G., J.M.A.), Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam, The Netherlands
3. Department of Clinical Chemistry (M.T.A.), Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam, The Netherlands
4. Department of Molecular Genetics (J.F.C.G.), Maastricht University, 6200 MD Maastricht, The Netherlands