More than 43 million Americans have osteoporosis or osteopenia, low bone density that is a marker for risk of fracture. That number is expected to increase to 61 million by 2020. Bone mineral accretion during growth and development in childhood is a critical determinant of the risk for osteoporosis later in life. Failure to achieve optimal bone density during childhood and adolescence results in suboptimal peak bone mass, which contributes to the risk for osteoporosis later in life. The NICHD conducts and supports research on bones and bone health as a way to understand healthy development and the origins of health and disease.
Institute Activities and Advances
Some Institute research is aimed at understanding the factors and mechanisms of normal bone growth, including the cellular, molecular, and genetic mechanisms involved with bone growth in children, as well as the factors that influence this growth, such as ethnicity and sex. The Institute's portfolio also includes studies of bone composition, including calcium, vitamin D, and other minerals, and ways to improve bone health, including weight-bearing physical activity and nutritional supplements.
Much of this research is supported through the NICHD's Pediatric Growth and Nutrition Branch (PGNB), which examines the developmental origins of health and disease to better understand and prevent chronic disease in adulthood. Branch-supported research includes (but is not limited to):
- Studies of growth factors, signaling molecules, and essential regulators involved in bone growth and fracture healing, in addition to ongoing studies of the effects of nutrition and physical activity on bone health.
- Research on physical activity as a vital component in the development of healthy bones, including the effects of weight-bearing physical activity on adaptations in bone macro-architecture structure.
- Research on fibroblast growth factors, important signaling molecules that regulate many stages of endochondral bone development and fracture repair. One of several research areas under study is the mechanism of action of signaling molecules that regulate the healing process.
- Studies of the effects of nutritional deprivation and chronic stress on bone accrual and fracture risk, including among adolescents with anorexia nervosa. Findings indicate that the alterations in cross-sectional variables of bone strength present in this population may have implications for fracture risk.
Within the Section on Growth and Development, part of the NICHD Division of Intramural Research (DIR), studies focus on the cellular and molecular mechanisms of longitudinal bone growth in childhood, including research on chondrocytes, cells that produce cartilage, and growth factors.
Other Institute research focuses on understanding abnormal bone and other tissue growth and development. In some cases, this abnormal growth results from genetic diseases that affect bone and other tissues directly. In other cases, a certain aspect of a disease or the interventions used to treat a disease lead to abnormal bone growth.
The Bone and Extracellular Matrix Branch within the DIR focuses on studies of osteogenesis imperfecta (OI)—a genetic disease that results in severe osteoporosis and lifelong disability—and other diseases that result from a defective extracellular matrix in bone, such as Ehlers-Danlos syndrome. Laboratory studies are aimed at understanding their genetic etiology and molecular and cellular mechanisms, and will yield insight into normal skeletal functioning. Clinical protocols of the Branch focus on improved clinical diagnosis and treatments. Branch research has identified the genes involved with different types of OI and with response to treatments for OI.
Some diseases, such as autism spectrum disorders (ASDs), and medications used to treat different conditions, such as HIV/AIDS, can also affect bone health, growth, and strength. The Institute supports research to understand how these effects occur and ways to ameliorate them. For example:
- The PGNB supports research on adverse effects of chronic illness and the therapies used to treat diseases of childhood on linear growth.
- The Maternal and Pediatric Infectious Disease Branch (MPIDB) supports studies of the contributions of certain HIV/AIDS medications to bone fragility, as well as whether vitamin D supplementation can reverse or reduce the medications' effects. The MPIDB also examines how HIV/AIDS treatments started in infancy affect overall growth and development in childhood and adolescence.
- The Division of Intramural Population Health Research (DIPHR) examines how dietary interventions commonly used to treat symptoms of ASDs —specifically gluten-free and casein-free diets—affect overall bone health and growth.
- Scientists in the Program on Reproductive and Adult Endocrinology within the DIR study the bone health outcomes of women with primary ovarian insufficiency (POI), a common type of infertility. Women with POI are at increased risk for osteoporosis because their bodies make lower levels of several hormones, including estrogen.
Other Activities and Advances
- Bone mineral density (BMD) during childhood is dependent upon linear growth, sexual and skeletal maturation, physical activity, dietary factors, and heredity. However, the ability to identify disorders of bone density that may accompany chronic illness, or their therapies, has been limited due to the lack of reliably collected reference data. The PGNB is conducting the Bone Mineral Density in Children Study (BMDCS) to learn more about this issue. The study is a population-based, longitudinal, and observational study of bone accretion in 2,000 healthy children and adolescents ranging from 5 years to 22 years old. The BMDCS includes five clinical centers that use a common protocol including dual-energy X-ray absorptiometry (DXA) measurements of the lumbar spine, femur, and radius; bone age X-ray; assessment of pubertal status, stadiometer height, and weight; and information on dietary calcium intake and physical activities.
- The data emanating from the BMDCS will provide BMD reference data for monitoring bone health in growing children. Likewise, the study's DXA data enable researchers and health care providers to assess changes of other body-composition components during childhood, puberty, and adolescence. For example, one of the aims of the BMDCS is to establish whether DXA values obtained in early puberty predict BMD at sexual maturity. These normative reference data will provide valuable guidance to children, young adults, and their parents and doctors on maintaining bone health.