Osteoporosis and Bone Physiology Susan Ott, M. D. UW Online CME Objectives Introduction Basic Bone Physiology What is Osteoporosis? Osteoporosis in Males Risk Factors for Osteoporosis Clinical Features of Osteoporosis Diagnosis of Osteoporosis Measuring Bone Density Indications T and Z Scores WHO Definitions Predicting Fracture Risk Reproducibility BAD Standardizing Results Markers of Bone Cell Activity Prevention of Osteoporosis Treatment of Osteoporosis Calcium Vitamin D Estrogen Seems Bisphosphonates Calcitonin Combination Therapy Experimental Therapies Evidence Tables Secondary Osteoporosis Steroids Cystic Fibrosis Osteomalacia Oncogenic Osteomalacia Renal Osteo dystrophy Transplant Bone Disease Kidney Liver Heart Lung Bone Marrow New Research Findings Image Gallery Osteoporosis Links Take a CME test on Osteoporosis and Bone Physiology Search this site Osteoporosis and Bone Physiology Osteoporosis in Males Osteoporosis is considered a woman's disease; however, one fifth of hip fractures occur in men. The exponential increase in hip fractures with age is seen in both genders, but the rise occurs about 10 years later in men than in women.
Males lose bone density with aging, but because males begin with a higher bone density, they reach osteoporotic levels at an older age than females. Also, men do not undergo the rapid bone loss associated with menopause. By the age of 90, about 17% of males have had a hip fracture, compared to 32% of females. Vertebral fracture prevalence in men is close to that in women.
In a study of 16, 119 European men and women aged 50-79, the overall prevalence of vertebral fractures (using a moderately specific method) was 12% for males and 12% for females. There was a higher incidence in the younger men, raising the possibility that some of the fractures were not related to osteoporosis, but to trauma sustained during their working life. In general bone physiology is similar in males and females. The major difference is in the levels of gonadal hormones.
Testosterone is probably anabolic at the bone level. In the peripheral tissue testosterone is converted to estrogen, which prevents excessive bone resorption. Estrogen is necessary to bone in males as well as females, as demonstrated by the rare cases of deficiency of the enzyme that converts testosterone to estrogen. These males have osteoporosis and are excessively tall due to failure to fuse growth plates.
The testosterone also increases muscle mass, which indirectly results in higher bone density. Cross-sectional studies of factors associated with decreased bone density in men show that increased age and decreased weight are important factors, as in women. Other factors include low activity level, poor dietary calcium intake, smoking, and blond hair. In some studies alcohol intake has no effect, but history of alcoholism is a risk factor for hip fractures.
Chronic bronchitis, gastric resection, thyroidectomy, hemiplegia, Parkinsonism, dementia and blindness are also risk factors for hip fractures. Some of these risks are due to gait and balance problems and not bone density. Men with low testosterone do not necessarily notice symptoms of decreased sexual functioning. Thus, testosterone levels should be measured in males with osteoporosis even if they don't have other symptoms of hypogonadism. Testosterone replacement for male osteoporosis has not been studied as well as estrogen replacement in women, but physiological evidence and short-term trials suggests it should be the first choice of therapy in men who have low serum levels. The dose starts at 100 mg every two weeks, increasing to 200 mg every two weeks.
This can be given as intramuscular injections of testosterone enanthate or cryproprionate. Scrotal or transdermal patches are also available, but they are more expensive. Males on testosterone replacement should have routine examinations of prostate, cholesterol, and liver function tests. The bone density of the spine can be expected to increase about 5% over the first year of therapy. Limited data suggest that males will respond to bisphosphonates. Of course, calcium, good diet, vitamin D, exercise, and avoiding falls are as important in men as in women.
Previous | Next (c) 1998, Susan Ott, M. D. These files were adapted from Dr. Ott's excellent Osteoporosis Web Site Release date: July 1, 1999 Expiration date: June 30, 2002 This page was last updated on 7/19/00; 4: 34: 03 PM with BBEdit and Frontier 6. 0 on a Macintosh running System 8. 6..