Bone mineral density and parameters of bone metabolism in patients with acromegaly

E. Hubina, P. Lakatos, L. Kovács, Cs. Horváth, S. Czirják, I. Szabolcs, M. Góth

Introduction: The bone mineral density and certain biochemical markers of bone metabolism in active and inactive acromegaly were investigated.

Patients and methods: 31 patients with active (23 female, 8 male, age: 30-74, median: 56 years, with minimum level of growth hormone during oral glucose tolerance test >= 2 ľg/l) and 18 patients with inactive disease (12 female, 6 male, age: 30-75, median: 48 years, with minimum level of growth hormone during oral glucose tolerance test < 2 ľg/l) were studied. Bone mineral density was measured at the lumbar spine, at the femoral neck and at the forearm. Bone markers were determined either in the urine (pyridinoline) or in the serum (total osteocalcin, undercarboxylated osteocalcin, endothelin).

Results: Bone mineral density Z- and T-scores were within the normal range both in active and inactive patients and these values did not differ between the two groups. Osteocalcin levels tended to be higher in the active group. In 6 patients the markers were measured both during the active and inactive phase of the disease. In these subjects the osteocalcin level was higher in the active period (p=0.042). Patients with inactive acromegaly had higher undercarboxylated osteocalcin than in active disease (49.5ą6.0 vs 34.5ą3.2, %, p=0.028). The other parameters of bone metabolism did not differ between active and inactive acromegaly. There was no correlation between the parameters of bone density, bone metabolism and growth hormone secretion, respectively.

Conclusions: patients both with active and inactive acromegaly have preserved bone mineral density. Growth hormone seems to have a positive effect on bone metabolism in terms of osteocalcin/undercarboxylated osteocalcin ratio, since it not only stimulates osteoblastic activity (osteocalcin) but reduces the amount of the biologically less effective undercarboxylated osteocalcin. This latter may have an impact on bone quality.