PINP - aminoterminal propeptide of type I procollagen - is a specific type I collagen metabolite which is released into the bloodstream during formation of new bone. Its concentration in serum is directly related to the rate of bone turnover.

In metabolic bone diseases such as osteoporosis, PINP is a sensitive indicator identifying patients with a high rate of bone turnover and, consequently, high risk of fracture. PINP is also a useful parameter for monitoring the effectiveness of antiresorptive and anabolic treatment.