Vitamin D insufficiency/deficiency in gastrointestinal disorders.

Vitamin D and calcium are critical for skeletal health. Their absorption from the intestine is negatively impacted by a number of gastrointestinal diseases and surgical procedures, leading to osteoporosis and/or osteomalacia. Diseases of the liver can impact the metabolism of vitamin D to its circulating form, 25(OH)D, as well as the production of carrier proteins, albumin and vitamin D-binding protein, that may alter the delivery of 25(OH)D and its active metabolite 1,25(OH)(2)D to target tissues, including the skeleton, again leading to bone disease. The clinician evaluating a patient with apparent osteoporosis and vitamin D deficiency/ insufficiency needs to consider a gastrointestinal etiology. Similarly, the clinician evaluating a patient with a gastrointestinal disorder needs to evaluate that patient for vitamin D deficiency and bone disease. Treatment involves adequate vitamin D and calcium supplementation to achieve normal serum 25(OH)D, PTH, and serum and urine calcium levels.