[Serum levels of the carboxyterminal telopeptide of type I collagen in patients with thyroid disorders].

Serum carboxyterminal cross-linked telopeptide of type I collagen (ICTP) levels, marker of bone resorption, were evaluated in 35 patients with hyperthyroidism (age range: 21-68 years) and in 35 with hypothyroidism (age range: 28-69 years). Data obtained were compared with those recorded in an age and sex matched control group. In patients with hyperthyroidism, serum ICTP levels were significantly higher than in controls (mean +/- SE: 9.1 +/- 0.7 vs 4.1 +/- 0.3 ng/ml; p < 0.0001). In patients with untreated hypothyroidism ICTP levels were significantly reduced (2.5 +/- 0.2 ng/ml, p < 0.0001); seven patients with hypothyroidism, evaluated after substitutive L-thyroxine treatment, showed a significant increase of ICTP levels (6th month: 5.9 +/- 0.7 ng/ml, p < 0.02). Taking into consideration all the data recorded in patients with both hyper- and hypothyroidism, serum ICTP levels were positively correlated with those of free T3 and free T4 and negatively correlated with those of TSH. In conclusion, our data show that repeated determinations of ICTP levels, which directly reflect the bone resorption activity, might be usefully employed in the evaluation of bone turnover in patients with thyroid disorders.