1. Departments of Endocrinology and Metabolism (S.N.v.d.C., G.A., H.P.S.), Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam
2. Clinical Chemistry (M.T.A., E.E.), Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, 1100 DD Amsterdam
3. Department of Endocrinology (J.A.R.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands