Urinary free and total hydroxyproline in hyperparathyroidism and the effect of removal of parathyroid adenoma

Abstract

The urinary excretion of total hydroxyproline was elevated above the upper limit of normal values in 8 out of 13 patients with surgically confirmed primary hyperparathyroidism. All patients with normal urinary total hydroxyproline excretion had normal plasma alkaline phosphatase levels and normal bone X-rays, whereas 3 of the 8 patients with increased total hydroxyproline excretion had increased plasma alkaline phosphatase levels, and 4 of these 8 patients showed evidence of bone involvement in X-rays. These results support the suggestion that the urinary excretion of total hydroxyproline may be a more sensitive index of bone involvement in hyperparathyroidism than plasma alkaline phosphatase or bone X-rays, but that even normal hydroxyproline excretion does not exclude bone involvement. After removal of the parathyroid adenoma, the urinary excretion of total hydroxyproline decreased in all 7 patients in whom this effect was studied, including 2 patients with initially normal urinary total hydroxyproline values.The ratio of free to total urinary hydroxyproline was determined in 9 patients with hyperparathyroidism, including 4 patients with normal urinary total hydroxyproline excretion. This ratio was found to be elevated in 8 out of 9 patients studied. The content of free serum hydroxyproline was normal in 3 of these 8 patients, suggesting that the increased ratio in the urine was probably due to renal effects of parathyroid hormone