Lack of hepatic metabolism of C-telopeptides of type I collagen

Measurement of aminoterminal propeptide of type I procollagen (PINP) in serum

The aminoterminal propeptide of type I procollagen (PINP) in serum is a sensitive indicator of the synthesis of type I collagen. Four assays are available for PINP, two of them (intact PINP assays) measure the intact propeptide and the other two (total PINP assays) also detect a smaller antigen in serum. In many clinical situations, these assays give similar information, but renal insufficiency increases the concentration of the smaller antigen, influencing both the apparent concentration of PINP and assay calibration. Serum PINP is mostly affected by changes in bone metabolism. In infants and children, the concentration is much higher than in adults. Serum PINP (s-PINP) is a useful indicator of disease activity in Paget's disease of bone, in bone metastases of osteoblastic nature, and in the follow-up of treatment of osteoporosis. The IFCC and IOF recently recommended the use of s-PINP as a reference marker for bone formation in studies concerning fracture risk assessment and treatment response.

Potential utility of high preoperative levels of serum type I collagen markers in postmenopausal women with primary hyperparathyroidism with respect to their short-term variations after parathyroidectomy

We evaluated short-term changes in serum amino-terminal procollagen propeptide (P1NP) and cross-linked C-terminal telopeptide (betaCTX) of type I collagen after parathyroidectomy (PTX) in 41 postmenopausal women with primary hyperparathyroidism (PHPT). Serum levels of 25-hydroxyvitamin D, intact PTH, calcium, phosphate, albumin, creatinine, P1NP, and betaCTX were measured before and 2 days after PTX. Their P1NP and betaCTX levels were compared with those measured in 41 normally menstruating and 30 postmenopausal controls. Fifteen of these 41 women had both pre-surgery P1NP and betaCTX concentrations above the upper limit noted in our postmenopausal controls [high turnover (HT) subgroup], while betaCTX levels were solely above the upper limit lastly mentioned in 11 women [high bone resorption (HBR) subgroup]. In addition, these two markers were within the postmenopausal control range in 12 of them [normal turnover (NT) subgroup]. A more significant decrease in postoperative betaCTX levels was observed in the 15 HT compared with the 12 NT PHPT women. The significant postoperative increase in P1NP levels observed in the 15 HT as well as in the 11 HBR was no longer significant in the 12 NT women. In conclusion, higher pre-surgery P1NP and betaCTX levels in post-menopausal PHPT women are associated with a preferential activation of bone formation over bone resorption after PTX.