CALCIUM-METABOLISM IN DIABETES-MELLITUS - EFFECT OF IMPROVED BLOOD-GLUCOSE CONTROL

Reduced bone mass occurring with increased frequency in diabetes melli tus has been attributed to poor blood glucose control but the pathogen etic mechanisms remain unknown. To evaluate the role of calcium metabo lism, 59 patients with diabetes and normal renal function (22 Type 1, 37 Type 2) were studied. In all patients plasma calcium (Ca), serum ph osphate (PO4)4 serum parathyroid hormone (PTH), and 24-h urinary calci um (uCa) were determined under both poor and improved control (for at least 7 days) as ascertained by four blood glucose determinations dail y. Improvement of blood glucose control (p=0.001) was associated with reduction of uCa both in Type 1 (6.9 +/- 1 vs 4.9 +/- 0.9 mmol day-1, mean +/- SEM, p=0.02) and in Type 2 patients (4.2 +/- 0.4 vs 3.2 +/- 0 .4 mmol day-1, mean +/- SEM, p=0.002). Considerably more Type 1 patien ts (10 out of 22) had PTH values below the detection limit (1.5 pmol l -1) during poor than during improved control (2 out of 22). Comparison between the two types of diabetes showed that in Type 1 under poor co ntrol, Ca and PTH were lower (p=0.03), while uCa was higher (p=0.003), and after improved control, only uCa continued to be higher (p=0.035) . These findings suggest that increased uCa excretion in association w itih 'functional hypoparathyroidism' (especially in Type 1 diabetes) i s observed during poor blood glucose control, and may be one of the fa ctors leading to reduced bone mass in diabetes mellitus.