E. Michael Lewiecki, MD, FACP, FACE is the vice president of the board of trustees at the National Osteoporosis Foundation. Here, he discusses the effects of bone health on the risk of osteoporosis.
E. Michael Lewiecki, MD, FACP, FACE
Vice President of the Board of Trustees, National Osteoporosis Foundation
How do hormone abnormalities increase the risk of osteoporosis?
Many endocrine diseases cause bone loss and fractures. This is why patients with osteoporosis are often evaluated for underlying hormonal problems and why patients with some endocrine diseases should be checked for osteoporosis.
Osteoporosis is caused by disruption of the normal process of bone remodeling. Our bones are in a constant state of remodeling, whereby bone is removed (resorbed) by osteoclasts and replaced (formed) by osteoblasts, occurring in about a million microscopic units throughout the skeleton. When bone remodeling is in a steady state, the amount of bone formed is equal to the amount resorbed and bone density is stable. This keeps our bones strong and healthy, replacing the entire skeleton approximately once every 10 years.
When the amount of bone formed does not fully replace what is resorbed, bone density decreases and osteoporosis may occur with bones that are weaker than normal and more likely to break. The examples below explain the connection between some common endocrine disorders and osteoporosis.
- Postmenopausal osteoporosis, the most common form of osteoporosis, is due to estrogen deficiency. Low estrogen levels in postmenopausal women alter the levels of small molecules in bones that regulate bone remodeling, with an increase in the activity of osteoclasts and osteoblasts and an imbalance of bone resorption being greater than bone formation. The net result is bone loss. Something similar happens in men with low testosterone levels, although bone loss typically occurs at a later age and is less severe than in women.
- Primary hyperparathyroidism is a common endocrine disorder that occurs in about 1 in 1,000 postmenopausal women. Excessive parathyroid hormone, usually coming from a single overactive parathyroid gland, causes a high rate of bone remodeling with an increase of calcium level in the blood and urine, resulting in bone loss and sometimes kidney stones. The treatment is surgical removal of the responsible parathyroid gland(s), which normalizes calcium levels and often improves bone density.
- Excessive thyroid hormone, whether it be intrinsic in origin, as with Grave’s disease, or due to excessive doses of thyroid replacement therapy, can also increase the rate of bone remodeling and cause bone loss. Treatment is correction of the underlying cause.
- Perhaps the most notorious endocrine cause of bone loss is excessive glucocorticoids. The main cause is medication, such as prednisone, used for the treatment of serious medical conditions, but can also be from diseases of the pituitary or adrenal glands that increase internal production of these hormones. Long-term exposure to high levels of glucocorticoids reduces the rate of bone formation and increases fracture risk.
What should people know about hormone replacement therapy?
Treatment with estrogen, with or without progesterone, is often used to control menopausal symptoms. Estrogen also has beneficial skeletal effects and is FDA-approved for prevention of osteoporosis. The North American Menopause Society suggests that this treatment be considered to prevent bone loss in women at risk for osteoporosis who are younger than age 60 years and within 10 years of the onset of menopause.
What can people do now to support their endocrine system and prevent osteoporosis?
Healthy lifestyle and good nutrition are essential for healthy bones and endocrine organs. The National Osteoporosis Foundation (NOF) recommends regular weight-bearing and muscle strengthening physical activity, a daily calcium intake of 1000 – 1200 mg, ideally from diet, and daily vitamin D intake of 800 -1000 IU for most adults age 50 years and older.
What is the relationship between menopause and osteoporosis?
The menopause transition can have important effects on the skeleton. An accelerated rate of bone loss of about 2.5 percent per year may begin about one year before the final menstrual period and continue for several years after. This is followed by a slower but continuing age-related rate of bone loss of about 1 percent per year. The NOF recommends that all women age 65 years and older have a bone density test and that younger postmenopausal women with risk factors for osteoporosis also be tested.
Visit the National Osteoporosis Foundation’s website www.nof.org for information about good bone health and preventing osteoporosis.The Endocrine Society is dedicated to advancing endocrinology and improving public health. Learn more here: www.endocrine.org/.