Basic Endocrinology

Osteoporosis

Osteoporosis is a disease characterized by reduced bone density and quality, leading to bone weakness and fragility and thus an increased risk of fractures, particularly of the hip, pelvis, wrist, and spine. Osteoporosis is often referred to as the "silent disease" because bone loss occurs gradually and without symptoms. The worldwide lifetime risk of incurring an osteoporotic fracture is 30-40% for women and approximately 13% for men. According to the World Health Organization (WHO), osteoporosis is second only to cardiovascular disease as a leading health problem. Women with premature menopause (age <45 years) and/or abnormal absence of menstrual periods (amenorrhoea) are at the greatest risk of developing osteoporosis. People with a family history of the disease, a low body mass index, and/or eating disorders are also more susceptible.

Many factors influence peak bone mass acquisition in both males and females, and endocrine factors are among the most prominent. Sex hormones, specifically estrogen and progesterone, appear to minimize the risk of osteoporotic fractures by reducing bone loss. Estrogen influences the rate of calcium absorption and deposition and thus controls bone remodeling. Estrogen deficiencies have been shown to accelerate bone turnover and resorption which can lead to osteoporosis. Because environmental contaminants have been shown to increase the activity of the liver enzymes that control the metabolism of estrogens and may thus alter circulating estrogen levels, there is concern that osteoporosis may be another adverse health outcome resulting from exposure to endocrine toxic chemicals.