SERUM CONCENTRATIONS OF CARBOXYTERMINAL CROSS-LINKED TELOPEPTIDE OF TYPE-I COLLAGEN (ICTP), SERUM TARTRATE-RESISTANT ACID-PHOSPHATASE, AND SERUM LEVELS OF INTACT PARATHYROID-HORMONE IN PARATHYROID HYPERFUNCTION

We have studied the levels of a new biochemical marker of bone resorpt ion, carboxyterininal cross-linked telopeptide of type I collagen (ICT P), in 26 healthy control subjects, 15 patients with primary hyperpara thyroidism (PHPT) and 17 patients with secondary hyperparathyroidism ( secondary HPT). Levels of ICTP in PHPT and secondary HPT have been cor related with those of serum tartrate resistant acid phosphatase-(TRAP) , another biochemical marker of bone turnover, and with serum levels o f intact parathyroid hormone (iPTH). The ICTP levels of the control gr oup were 2.07 +/- 0.58 mug 1(-1), n = 26, range 1.3-3.2. They were ind ependent of sex and age in the studied age range (30-62 years). The IC TP levels of PHPT patients were 3.5 +/- 3.5 mug 1-1, mean +/- SD, rang e 0.5-12.2 mug 1(-1), significantly higher than those of control subje cts (p < 0.05). We found a significant linear correlation between valu es of ICTP and iPTH levels (p < 0.01), between values of ICTP and seru m activity of TRAP (p < 0.01) and between iPTH and TRAP levels (p < 0. 01) in patients with PHPT. The ICTP levels in patients with secondary HPT were higher than those of patients with PHPT, 46 +/- 37 mug 1(-1), range 12-167 mug 1(-1) (p < 0.00 1) due to the impaired renal clearan ce of this peptide. We did not find a significant linear correlation b etween values of ICTP and iPTH levels in the serum of patients with se condary HPT, although we found a significant correlation between level s of ICTP and levels of TRAP, both biochemical markers of bone turnove r. The above results indicate that the new biochemical marker of bone turnover, serum ICTP, could be used as an index of bone resorption in states of parathyroid hyperfunction, if renal function is maintained.