Iliac crest bone mass and remodelling in acromegaly

Abstract

Iliac crest bone biopsies from 18 patients with active acromegaly, of whom 11 had received tetracycline double-labeling, were evaluated by quantitative histomorphometry and compared with age- and sex-matched normal controls. A significant increase (P < 0.01) was found in both cortical (175%) and trabecular (130%) bone mass. In trabecular bone, resorption surfaces and active (tetracycline-labeled) and total formation surfaces were increased (P < 0.05 and P < 0.01, respectively) causing an enhanced bone turnover at tissue level (P < 0.01). The increased trabecular bone mass indicates a positive net balance per remodeling cycle and, therefore, larger than normal bone remodeling units, which in part may explain the increased bone turnover at tissue level. The activity of the osteoblasts active in mineralization (the appositional rate) was increased (P < 0.01) and positively related to the fasting serum growth hormone levels (Rs = 0.69, P < 0.05). The average activity of active and inactive osteoblasts (bone formation rate at basic metabolic unit level) was insignificantly increased. The proportion of active (tetracycline labeled) to nonactive formation surfaces was normal. The bone changes were unrelated to serum levels and urinary excretions of Ca and P or to renal excretion of total and nondialyzable hydroxyproline or cAMP.