[1] Vrije Univ Amsterdam, Dept Clin Chem, Endocrine Lab, Amsterdam UMC,Amsterdam Gastroenterol & Metab, Amsterdam, Netherlands
[2] Univ Amsterdam, Dept Clin Chem, Endocrine Lab, Amsterdam UMC, Amsterdam, Netherlands
[3] Leiden Univ, Dept Clin Chem & Lab Med, Med Ctr, Leiden, Netherlands