Osteopenia in insulin-dependent diabetes mellitus; prevalence and aspects of pathophysiology

The objective was to evaluate the prevalence and severity of osteopenia in patients with uncomplicated insulin-dependent diabetes mellitus (IDDM) and to obtain more information on the pathophysiology of diabetic osteopenia. I n 35 patients with uncomplicated IDDM (21 men and 14 women; age 37.6+/-9.9 yr; duration of disease 8.5+/-3.5 years) bone mineral density was measured by dual energy X-ray absorptiometry (DEXA). In addition, markers of bone fo rmation [plasma insulin-like growth factor I (IGF-I), serum alkaline phosph atase (ALP), serum bone alkaline phosphatase (BAP) and serum osteocalcin] a nd bone resorption [urinary excretion of calcium and of the cross-linked N- telopeptide of type 1 collagen, both corrected for the excretion of creatin ine] were measured in the diabetic patients and in 33 healthy controls, mat ched for sex, age, height, weight and body mass index (BMI). In 67% of the diabetic men and 57% of the diabetic women osteopenia of the femoral neck a nd/or the lumbar spine (T-value less than or equal to-1 SD) was present. Fo urteen percent of the male patients, but none of the female patients, met t he criteria for osteoporosis (T-value less than or equal to-2.5 SD). In the whole group of diabetic patients the mean plasma IGF-I level tended to be lower (p<0.10) as compared to that in the controls. In the diabetic patient s with femoral neck osteopenia, the mean plasma IGF-I level was significant ly lower (p<0.05) than in those without osteopenia at this site. There were no differences in the mean serum ALP, BAP and osteocalcin levels between t he diabetic patients and the controls, nor between the diabetic patients wi th and without femoral neck osteopenia. Considering only the male diabetic patients, significantly lower mean plasma IGF-I (-26%), serum ALP (-24%) an d serum osteocalcin (-38%) levels were present in the patients with femoral neck osteopenia than in those without osteopenia at this site, suggesting lowered bone formation. The bone resorption markers were similar in all (su b)groups of diabetic patients and not different between diabetic patients a nd controls. Bone mineral density (BMD) did not correlate with plasma level s of glycosylated hemoglobin (HbA(1c)). BMD values were not related to any of the bone resorption or formation markers, except for plasma IGF-I both i n the femoral neck (r=+0.38, p=0.026) and the lumbar spine (r=+0.34, p=0.04 3). Our data demonstrate that at least in male patients with IDDM, osteopen ia is the consequence of a lowered bone formation with a predominance of bo ne resorption over formation. (C) 2000, Editrice Kurtis.