Nitric oxide: novel therapy for osteoporosis

Relative nitric oxide (NO) deficiency is responsible for many pathophysiological processes, including in postmenopausal women providing a plausible biological basis for use of NO replacement therapy in humans. Excess or inappropriate local production of NO aggravates bone destruction in some diseases such as septic shock, rheumatoid and other inflammatory arthropathies.

A variety of in vitro and in vivo data have revealed the efficacy of nitroglycerin and nitrates on bone cells. Since some part of the beneficial effects of estrogen on bone is mediated via the NO-cGMP pathway, NO donor therapy is an attractive alternative to estrogen therapy to prevent and treat osteoporosis. When the body cannot generate adequate amounts of NO for biological homeostasis, administration of exogenous NO or prolongation of the actions of endogenous NO are practical ways to supplement NO, especially in postmenopausal women.

Postmenopausal NO deficiency is rectified with hormone replacement therapy, which enhances local production of NO. Declining local NO production secondary to estrogen deficiency in postmenopausal women, and perhaps in older men, could be one of the key reasons for age-related increased incidences of cardiovascular events, sexual dysfunction as well as osteoporosis. Thus, in addition to supplementation of NO compounds in acute situations such as alleviating angina and erectile dysfunction, it could be a valuable addition to the armamentarium of therapies for chronic conditions such as osteoporosis.