CARBOXY-TERMINAL PROPEPTIDE OF TYPE-1 PROCOLLAGEN (P1CP) AND CARBOXY-TERMINAL TELOPEPTIDE OF TYPE-1 COLLAGEN (1CTP) AS SENSITIVE MARKERS OFBONE METABOLISM IN THYROID-DISEASE

We measured serum levels of the carboxy-terminal propeptide of type 1 procollagen (P1CP) as a marker of bone formation and the carboxy-termi nal telopeptide of type 1 collagen (1CTP) as a marker of bone resorpti on by RIA in sera from 40 Graves' disease patients and 14 Hashimoto's disease patients before and during treatment. The serum P1CP levels of the untreated Graves' disease were significantly higher than in the c ontrols (176.8 +/- 93.5 vs. 107 +/- 35 ng/ml, P<0.01), and these level s decreased significantly during treatment with antithyroid drugs. The re was a significant statistical correlation between serum P1CP levels and serum total alkaline-phosphatase activity (r=0.61, P<0.01) in the patients with Graves' disease and Hashimoto's disease as a whole. 1CT P levels were also significantly increased in untreated Graves' patien ts (6.5 +/- 2.8 compared with 2.7 +/- 1.1 ng/ml in normal subjects, P< 0.01). The P1CP/1CTP ratio, which reflects the relative ratio of bone formation to bone resorption, was lower than normal in untreated Grave s' disease, but increased following the normalization of thyroid funct ion. The results of this study suggest that the measurement of serum P 1CP and 1CTP levels may be useful in evaluating bone metabolism in thy roid disease.