Changes of vitamin D3 serum concentrations at the onset of immune-mediated type 1 (insulin-dependent) diabetes mellitus.

Several hormones such as 1,25-dihydroxy-vitamin D3 (1,25-(OH)2D3), alpha-MSH, or ACTH have been found to interact extensively with the immune system. In view of the immune-mediated nature of Type 1 (insulin-dependent) diabetes mellitus, 49 recently diagnosed diabetic patients were investigated in terms of serum 1,25-(OH)2D3-levels, 25-hydroxyvitamin D3(25-(OH)D3), alpha-MSH and ACTH, and compared with 42 healthy controls. A marked decrease of 1,25-(OH)2D3-levels was found at onset of Type 1 (insulin-dependent) diabetes compared to normal controls (39 +/- 2 vs 55 +/- 4 pg/ml, p less than 0.01). Grouping patients according to season (winter or summer) of diabetes onset and blood sampling, it was demonstrated that the decrease of 1,25-(OH)2D3 was primarily present during summer and due to a loss of the seasonal rhythm of this hormone observed in healthy controls (summer: patients vs controls 41 +/- 2 vs 63 +/- 4 pg/ml, p less than 0.001; winter: 37 +/- 3 vs 33 +/- 3 pg/ml, n.s.). Serum concentrations of 25-(OH)D3 were closely correlated with those of 1,25-(OH)2D3, both in controls (r = 0.55, p less than 0.002) and diabetic patients (r = 0.41, p less than 0.05), yielding a similar loss of seasonal variation also of this vitamin D3 metabolite in Type 1 (insulin-dependent) diabetic patients. No difference was found in the mean and median values of alpha-MSH and ACTH between IDDM patients and controls, although patients exhibited much higher variation of alpha-MSH levels than did controls.(ABSTRACT TRUNCATED AT 250 WORDS)