The Williams syndrome is a disease in which supravalvular aortic stenosis, an elfin facies, mental retardation and other congenital defects are sometimes associated with abnormal vitamin D and calcium metabolism. Whereas some patients have been reported to show increased sensitivity to vitamin D or an exaggerated response of serum 25-hydroxyvitamin D {25(OH)D} to administration of vitamin D and to have hypercalcemia caused by increased circulating 1,25-dihydroxyvitamin D{1,25(OH)2D} in infancy and early childhood, most patients have normal calcium metabolism and normal values for circulating 25(OH)D and 1,25(OH)2D. We propose to carry out further studies of vitamin D metabolism to elucidate the mechanism(s) for abnormal vitamin D metabolism. We will determine the response of serum 1,25(OH)2D to administration of 1,25(OH)2D3. Measurement of the 1,25(OH)2D in the patients compared to normal subjects will be the primary outcome.

Age 18 years to 50 years of age, patients and normal subjects