Parathyroid hormone, but not vitamin D, is associated with the metabolic syndrome in morbidly obese women and men: a cross-sectional study - Hjelmesaeth, J; Hofso, D; Aasheim, E T; Jenssen, T; Moan, J; Hager, H; Roislien, J; Bollerslev, J (Cardiovasc Diabetol, 2009)