Bone metabolism in rheumatoid arthritis compared with postmenopausal osteoporosis.

Calcium and bone metabolism in 29 rheumatoid arthritis (RA) patients were compared with those in 27 postmenopausal osteoporotic patients. Signs of vitamin D deficiency were found in 20 RA patients, including 12 who took recommended amounts of vitamin D in their diets and were exposed to sufficient sunlight, and in none of the osteoporotic patients. There were no signs of malabsorption. In six out of 15 patients we found increased liver enzyme activity, which may have a role in vitamin D metabolism. We propose the influence of non-steroidal anti-inflammatory drugs (NSAIDs) on vitamin D metabolism in the liver as a possible explanation.