The combined effect of vitamin D and parathyroid hormone concentrations on glucose homeostasis in older patients with prediabetes: A cross-sectional study - Karras, S N; Anagnostis, P; Antonopoulou, V; Tsekmekidou, X; Koufakis, T; Goulis, D G; Zebekakis, P; Kotsa, K (Diab Vasc Dis Res, 2018)