The skeleton provides structure and support for the body: it protects vital organs from injury, anchors the muscles, and allows us to move. It also stores minerals such as calcium and phosphorus to help keep our bones strong, and as a reservoir for other uses in the body. Our bones are continually turning over (remodeling) as new bone is made and old bone is broken down. When you’re young, your body makes new bone faster than it breaks down old bone, and your bone mass increases. Most people reach their peak bone mass around age 30. It is important to maintain bone mass as we age to prevent the development of osteoporosis (bone loss) and risk of fractures. Measurement of certain blood biomarkers can aid in assessment of bone health and efficacy of treatments.
Calcium, Phosphorus, Vitamin D3, Parathyroid Hormone
Calcium is a structural component of bones and teeth and is important for body processes such as nerve transmission, muscle contraction, hormone and neurotransmitter synthesis, enzyme activation, and blood clotting. Plasma calcium levels are kept constant by the actions of hormones such as vitamin D and parathyroid hormone (PTH). Vitamin D sufficiency is important for the body to properly absorb dietary calcium. Vitamin D is also a key modulator of immune function and has anti-inflammatory properties, helping to prevent infections and autoimmune diseases (e.g., rheumatoid arthritis). Phosphorus is important for strong bones, acid-base balance in the kidneys, and growth/repair of body tissues.
C-Terminal Telopeptide (CTX), Osteocalcin
Maintenance of healthy bones involves a balance between bone-building by osteoblasts and bone demineralization by osteoclasts in a process of finely-regulated bone turnover. C-Terminal telopeptide (CTX) is a marker of bone resorption, while osteocalcin is a widely accepted marker of bone formation/turnover. Both markers are used to aid in the diagnosis of medical conditions associated with increased bone turnover, and to monitor response to treatment.
Bone turnover markers are elevated during childhood, growth, and fracture healing, but are usually balanced in these cases and of no diagnostic value. However, many diseases, including hyperthyroidism, osteomalacia and rickets, and bone cancer, can result in accelerated bone turnover. Unbalanced bone turnover is also found in age-related and postmenopausal osteopenia and osteoporosis.