Vitamin D and parameters of calcium homeostasis in inpatients with and without Type 2 diabetes mellitus

Aim: We investigated inpatients with and without Type 2 diabetes mellitus, aged over 60 yr, to compare their vitamin D status and calcium homeostatic parameters. Materials and methods: We studied 140 patients consecutively admitted to our Internal Medicine Unit during the year 2010 (61 from November to April, 79 from May to October). The sample encompassed 70 patients with and 70 without diabetes. At admission we measured serum calcium (Ca), phosphate (P), sodium (Na), potassium (K), creatinine (Cr), alkaline phosphatase total activity (AP), albumin adjusted serum calcium (Caalb adj), 25 hydroxy-vitamin D (25OHD), PTH, and 24-h urinary Na/Cr (uNa/Cr), K/Cr (uK/Cr), Ca/Cr (uCa/Cr), P/Cr (uP/Cr) ratios, and calcium excretion (Ca ex). Results: 25OHD levels of patients with and without diabetes did not significantly differ. In patients without diabetes recruited from November to April, 25OHD levels were significantly lower than those from May to October, whilst patients with diabetes did not show a significant seasonal variation. PTH had opposite non-significant seasonal variations, and negatively correlated with 25OHD in both groups of patients. This correlation was lost after adjusting for age and body mass index in patients with diabetes. These inpatients had higher serum P and lower uP/Cr, according to lower PTH. Their serum glucose negatively correlated with uCa/Cr and Ca ex, contrary to inpatients with other diseases. Instead, uCa/Cr and Ca ex correlated with uNa/Cr only in patients without diabetes. Conclusions: Inpatients with diabetes did differ from those with other disorders for vitamin D status and calcium-phosphate homeostatic mechanism.