Premenopausal osteoporosis associated with vitamin D-responsive calcium malabsorption. A case report.

A premenopausal woman with severe osteoporosis was found to have impaired calcium absorption, without other evidence of intestinal malabsorption. Although circulating levels of 25-OH-vitamin D and 1,25-(OH)2-vitamin D were normal, calcium absorption improved markedly following two weeks of treatment with synthetic 1,25-(OH)2-vitamin D. This suggests that a partial intestinal resistance to the actions of 1,25-(OH)2-vitamin D contributed to the development of her osteoporosis. This case report demonstrates the feasibility of using the calciuric response to a standard oral calcium load to screen for impaired calcium absorption in osteoporotic patients.