Total and non-dialyzable urinary hydroxyproline in acromegalics and control subjects

Abstract

Abstract. The urinary excretion of total and non-dialyzable hydroxyproline (HYP) containing peptides has been studied in 25 patients with active acromegaly and 44 control subjects — all kept on a collagen free diet. Acromegalics had a greater excretion of both total and non-dialyzable HYP than controls, indicating an increased turn-over of collagen/bone matrix. The amounts of total and non-dialyzable HYP excreted in acromegalics were significantly correlated to mean fasting growth hormone levels. Both acromegalics and controls exhibited a significant coupling between the excretion of total and non-dialyzable HYP. Female control subjects demonstrated an age-dependent decrease in the excretion of both total and non-dialyzable HYP, whereas no such age-dependence could be observed in males. Age seemed to have a greater effect on the non-dialyzable fraction than on the total HYP excretion. These results may imply that collagen/bone matrix turn-over declines with age and that bone formation declines at a more rapid rate than resorption. In acromegalics the ratio of non-dialyzable to dialyzable HYP was not significantly different from control values, indicating that although turn-over is increased the actual matrix formation rate is normal in acromegaly. No correlation was found between serum or urinary parameters of calcium/phosphate metabolism or the urinary excretion of 3',5'-cyclic adenosine monophosphate and total or non-dialyzable HYP in acromegalics or controls.