Further evaluation of the significance of urinary hydroxyproline determinations in the diagnosis of thyroid disorders

Abstract

The urinary excretion of total hydroxyproline was determined in 262 patients with various thyroid disorders and in 47 euthyroid patients with elevated serum protein-bound iodine (PBI) but without thyroid disease. The values were compared with normal values (limits of ± 2 S.D.) in 92 children and in 72 adults 18 to 55 years of age, reported previously from our laboratory. In addition, normal values were determined in 53 adult euthyroid patients over 55 years of age. In adult patients, the urinary excretion of hydroxyproline was increased in hyperthyroidism above the upper limit of normal values in 107 out of 111 patients 18 to 65 years of age and in 10 out of 14 patients over 65 years of age. In hypothyroidism the urinary excretion of hydroxyproline was decreased below the lower limit of normal values in 22 out of 33 patients, and PBI was decreased in 24 of these patients. In the euthyroid patients with various thyroid disorders the urinary excretion of hydroxyproline was within the limits of normal values in 63 out of 68 patients. In an additional group of 47 patients with elevated PBI without hyperthyroidism, the urinary hydroxyproline values were within the limits of normal values in 46 cases. In children, the hydroxyproline values were above the upper limit of normal values in 10 out of 13 patients with hyperthyroidism, and below the lower limit of normal values in all 23 patients with hypothyroidism. The results support the earlier suggestion that determination of urinary hydroxyproline excretion may be a useful supplement to existing laboratory tests for the diagnosis of disturbances of thyroid function. The reliability of this test is high in cases of hyperthyroidism in a dult patients, and in cases of hypothyroidism in children.