Causes

Men and Androgens and Estrogen. In men, the most important androgen (male hormone) is testosterone, which is produced in the testes. Other androgens are produced in the adrenal glands. Androgens are converted to estrogen in various parts of a man’s body, including bone.

Click the icon to see an image of the adrenal glands.

Studies have suggested that the loss of estrogen as well as testosterone may contribute to bone loss in elderly men. In one study, elderly men were first given a drug that blocked their normal hormones and then were given estrogen and testosterone patches. When the estrogen patch was removed, the bone breakdown process accelerated. When both patches were removed, the number of the bone-building cells (the osteoblasts) decreased. In other words, both hormones appeared to be integral to bone function in men.

Vitamin D and Parathyroid Hormone Imbalances

Low levels of vitamin D and high levels of parathyroid hormone (PTH) are associated with hip fracture in women after menopause:

• Vitamin D is a vitamin with hormone-like properties. It is essential for the absorption of calcium into the bone and for normal bone growth. Lower levels result in impaired calcium absorption, which in turn causes an increase in PTH.
• Parathyroid hormone (PTH) is produced by the parathyroid glands. These are four small glands located on the surface of the thyroid gland. They are the most important regulators of calcium levels in the blood. When calcium levels are low, the glands secrete more PTH, which then increases blood calcium levels. High persistent levels of PTH stimulate bone resorption (bone loss).

Click the icon to see an image of the benefits of vitamin D.

Click the icon to see an image of the sources of vitamin D.

Click the icon to see an image of the parathyroid glands.

Genetic Factors

Several studies on family members, including twins, have strongly suggested that genetic factors help determine bone density. Some examples include the following:

• Of particular interest are genetic factors that affect vitamin D, a critical nutrient for calcium absorption in the body.
• Many studies are looking at abnormalities in genes that may cause deficiencies in estrogen receptors, molecules that help estrogen work on cells. Estrogen is important in maintaining bone density in both men and women.