ENDOCRINE CAUSES OF BONE-DISEASE

Circulating hormones and growth factors and many paracrinic factors no rmally regulate skeletal metabolism. The right hormones and growth fac tors in the right amount and at the right times are very important for the development, growth, and maintenance of the skeleton. Growth fact ors arrive at the bone from the circulation or are produced locally by a variety of cells present in bone. Skeletal cells synthesize insulin like growth factors I and II (IGF-1 and IGF-II), transforming growth f actors-beta 1, 2, and 3, bone morphogenetic proteins (BMP), fibroblast s growth factors, platelet-derived growth factors, prostaglandins, and a variety of cytokines of the immune system.(6) Circulating hormones interact with these local paracrine factors in the regulation of bone remodeling. Hormonal deficiencies or excesses may thus affect the achi evement of peak bone mass, its maintenance during maturity, and the ra te of bone loss that accompanies aging. Most of these endocrine effect s on bone become clinically apparent only after many years of hypersec retion or deficiency of the respective hormones. Elderly persons are a t a particular disadvantage because, superimposed on postmenopausal an d senile osteoporosis, the endocrine osteopathies accelerate the rate of bone loss. Many endocrinopathies have only a transient deleterious effect on the skeleton. Once the endocrinopathy is cured or improved, there is increased bone formation in an effort to recover the mineral density lost. Unfortunately, the recovery is frequently incomplete, an d bone density does not return entirely to normal. This lack of full r ecovery is even more marked in elderly persons.