Iliac crest bone mass and remodelling in acromegaly

Abstract

Abstract. Iliac crest bone biopsies from 18 patients with active acromegaly, of whom 11 had received tetracycline double-labelling, 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-labelled) and total formation surfaces were increased (P < 0.05 and P < 0.01, respectively) causing an enhanced bone turn-over at tissue level (P < 0.01). The increased trabecular bone mass indicates a positive net balance per remodelling cycle and, therefore, larger than normal bone remodelling units, which in part may explain the increased bone turn-over 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 (BMU) level) was insignificantly increased. The proportion of active (tetracycline labelled) to non-active formation surfaces was normal. The bone changes were unrelated to serum levels and urinary excretions of calcium and phosphorus or to renal excretion of total and non-dialyzable hydroxyproline or cAMP.