Intact N-Terminal Propeptide of Type 1 Procollagen

Indicator of type I collagen turnover.

Results of this assay should be used in conjunction with pertinent clinical information for making diagnostic and therapeutic decisions. This assay is not recommended for use as a screening procedure to detect the presence of osteoporosis in the general population. When evaluating subsequent samples, collect the samples at the same time of the day, as there is a diurnal variation of PINP with the values being higher at night. PINP is metabolized in the liver. Severe liver disease may affect clearance from the circulation and give rise to elevated serum PINP levels.

Approximately 90% of the organic matrix of mammalian bone consists of type 1 collagen that is cross-linked at the N-terminal and C-terminal ends.1 This highly cross-linked structure provides for the basic fabric and tensile strength of bone tissue.1,2 The collagen infrastructure of bone undergoes a continuous process of remodeling that involves osteoclast-mediated bone resorption and osteoblast bone formation. Bone collagen is derived from type 1 procollagen, which consists of three amino acid chains that are intertwined to form a rod-like helix.2 Type 1 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 (P1NP) 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, P1NP can be useful in the assessment of skeletal remodeling under normal and abnormal conditions. P1NP has used to monitor bone turnover in postmenopausal women3-6 and to monitor the effect of antiresorptive and anabolic therapy of bone metabolism.7-19 P1NP has also proved useful in the monitoring of treatment of patients receiving teriparatide therapy.20,21 The determination of P1NP has been used to assess increases in type I collagen turnover in Paget disease of bone.22-24 P1NP measurement has also been used to assess bone metastatic activity in a number of malignancies and in predicting survival.