P1NP

Ranges are printed separately for men, premenopausal and postmenopausal women by many labs and differ between assays; it is much higher in children and teenagers.

P1NP is a fragment released into the blood when new collagen is laid down to form bone. It is a marker of how actively bone is being built, the other half of the skeleton's rebuilding cycle from CTX. The test measures the fragment in a blood sample and is less affected by meals and time of day than CTX.

Doctors use it to check that a bone-building or bone-protecting medicine is having an effect, usually a few months after starting, and in Paget's disease, kidney bone disease and when looking into an unexplained raised alkaline phosphatase.

• Growth in childhood and adolescence, and healing fractures
• The years after the menopause
• Bone-building medicines such as teriparatide, in the months after starting
• Paget's disease and cancer that has spread to bone
• Overactive parathyroid or thyroid glands
• Low vitamin D and softening of the bones
• Reduced kidney filtering, with some assays

• Bisphosphonates, denosumab and hormone replacement, which slow bone turnover
• Long-term steroid tablets
• Underactive thyroid
• Older age in men, by a small amount

• A healing fracture raises it for weeks to months
• Bed rest and immobility change it
• Different assays (total versus intact P1NP) give different numbers and are not interchangeable

Fasting is not essential, but a morning sample taken at the same time on each occasion, and followed within one lab, gives the most reliable trend.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.