Causes

Because the patterns of reforming and resorbing bone often vary from patient to patient, doctors believe several different factors account for this problem. Important chemicals (estrogen, testosterone, parathyroid hormone, and vitamin D) and blood factors that affect cell growth are involved with this process. Changes in levels of any of these factors can play a role in the development of osteoporosis.

The Role of Sex Hormones in Bone Breakdown

Although normally associated with women, sex hormones play a role in osteoporosis in both genders, most likely by controlling the development and activity of both osteoclasts (bone breakers) and osteoblasts (bone builders).

Women and Estrogen. A woman experiences a rapid decline in bone density after menopause, when her ovaries stop producing estrogen. Estrogen comes in several forms:

• The most potent form of estrogen is estradiol. Estradiol deficiency appears to be a very strong factor in the development of osteoporosis.
• The other important but less powerful estrogens are estrone and estriol.

The ovaries produce most of the estrogen in the body, but it can also be formed in other tissues, such as the adrenal glands, body fat, skin, and muscle. After menopause, some amounts of estrogen continue to be manufactured in the adrenals and in peripheral body fat. Even though the adrenals and ovaries have stopped producing estrogens directly, they continue to be a source of the male hormone testosterone, which converts into estradiol.

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Osteoporosis Introduction

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Osteoporosis Risk Factors

Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)