Indicator of type I collagen turnover
No radioactive isotopes administered 48 hours prior to venipuncture
Immediately following collection, mix sample by gently inverting 5 times
Gold serum separator (SST) tube
Premenopausal: 19−83 μg/L
Postmenopausal: 16−96 μg/L
Approximately 90% of the organic matrix of mammalian bone consists of type I collagen that is cross-linked at the N-terminal and C-terminal ends. This highly cross- linked structure provides for the basic fabric and tensile strength of bone tissue. The collagen infrastructure of bone undergoes a continuous process of remodeling that involves osteoclast mediated bone resorption and osteoblast mediated bone formation. Bone collagen is derived from type I procollagen, which consists of three amino acid chains that are intertwined to form a rod-like helix. Type I procollagen has propeptide extensions at both ends of the molecule, which are removed by specific proteinases before the collagen molecules are assembled into collagen fibers. The cleaved propeptides can be found in the circulation where their concentration reflects the synthesis rate of type I collagen. The serum concentration of the amino- terminal propeptide of type I procollagen (PINP) is directly proportional to the amount of new collagen produced by osteoblasts. Metabolic bone diseases are characterized by imbalances in bone turnover that occur as the result of an uncoupling between bone formation and resorption. As an indicator of type I collagen production, PINP can be useful in the assessment of skeletal remodeling under normal and abnormal conditions. PINP can be useful in the assessment of skeletal remodeling under normal and abnormal conditions. PINP has been used to monitor bone turnover in postmenopausal women and to monitor the effect of antiresorptive and anabolic therapy of bone metabolism. PINP has also proved useful in the monitoring of treatment of patients receiving teriparatide therapy. The determination of PINP has been used to assess increases in type I collagen turnover in Paget's disease of bone. PINP measurement has also been used to assess bone metastatic activity in a number of malignancies and in predicting survival.