Changes in bone metabolism during treatment of acromegaly

Bone metabolism was studied in 17 acromegalic patients, who responded to either medical treatment with bromocriptine (12 patients), or to transsphenoidal surgery (5 patients). Parameters of bone turnover decreased, e.g. serum acid phosphatase (9.2 +/- 0.7 vs 8.1 +/- 0.6 U/l, P less than 0.05) and the ratio of hydroxyproline/creatinine (33.6 +/- 4.4 vs 18.3 +/- 2.0, P less than 0.01) in the urine. No changes were observed in parathyroid function or concentrations of calcitonin. Serum 1,25-dihydroxycholecalciferol decreased (32.6 +/- 3.6 vs 20.6 +/- 1.8 ng/l, P less than 0.01) and 24,25-dihydroxycholecalciferol increased (4.3 +/- 0.6 vs 6.7 +/- 1.0 micrograms/l, P less than 0.05). No correlation between the percentual changes in serum growth hormone levels and 1,25-dihydroxycholecalciferol was found, suggesting an indirect effect of growth hormone on the renal 25-hydroxycholecalciferol-1-alpha-hydroxylase. The possible mechanisms involved are discussed, including the effects of growth hormone and somatomedin on bone.