Bone mass is largely genetically determined, but environmental factors also contribute. Greater muscle strength and physical activity are associated with higher bone mass, while radial bone loss is greater in cigarette smokers or those with a moderate alcohol intake. A common secondary cause of osteoporosis in men is hypogonadism. There is increasing evidence that estrogens are important in skeletal maintenance in men as well as women. Conversion of androgens to estrogens occurs.
Human models exist for the effects of estrogens on the male skeleton.
Gastrointestinal disease makes patients susceptible to bone disease as a result of intestinal malabsorption of calcium and vitamin D. Hypercalciuria and nephrolithiasis, anticonvulsant drug use, thyrotoxicosis, immobilization, liver and renal disease, multiple myeloma and systemic mastocytosis have all been associated with osteoporosis in men. In the future, parathyroid hormones may be an effective treatment for osteoporosis, particularly in patients in whom other treatments, such as bisphosphonates, have failed. Studies of changes in BMD with IGF-I treatment in osteoporotic men and women are underway. Osteoporosis in men will become an increasing worldwide public health problem over the next 20 years, so it is vital that safe and effective therapies for this disabling condition become available. However, GHD is a syndrome that affects patients of all ages.