Estrogen not Cause of Osteoporosis

Photo: X-ray of a broken leg

Researchers challenge the view
that hormones are responsible for
developing osteoporosis; © SXC

Aging and the body’s increased inability to defend against bone-damaging molecules produced through a process known as oxidative stress are most directly responsible for the bone-weakening disease – and perhaps other age-related diseases, reported researchers.

Researchers found that age weakens the defenses against oxidative stress. In particular, an age-related loss of certain proteins that defend against oxidative stress increase the risk of osteoporosis. The scientists say conditions such as a loss of estrogen can further decrease the molecular defenses against oxidative stress.

“This emerging evidence provides a paradigm shift from the ‘estrogen-centric’ view of what causes osteoporosis to one in which these age-related mechanisms are the main protagonists and other changes – including the reduction of estrogen – accentuate them”, says lead researcher Stavros Manolagas.

Manolagas pointed to studies that showed bone loss in both women and men – who also can develop osteoporosis – begins as early as the early part of the third decade, which is long before any change in sex hormone production. He said other research showed age as a main factor in compromised bone strength and increased risk of bone fractures.

In the most research, scientists identified a specific family of proteins that served as a defense mechanism against oxidative stress. When the proteins, called forkhead box transcription factors, were removed in young mice, oxidative stress increased and bone weakness developed. When the protein was increased, oxidative stress decreased and the number of bone-forming cells increased and bone mass improved. “These proteins that defend against oxidative stress are indispensable for maintaining bone mass,” Manolagas said.

The proteins constantly defend against oxidative stress to ensure a normal healthy life span, he said. With age the oxidative stress begins to overwhelm the defense mechanisms. “Now we will look for what specifically causes the defense mechanisms against oxidative stress to fail over time,” he said.

MEDICA.de; Source: University of Arkansas for Medical Sciences