ABSTRACT
Vitamin D is required by humans of all ages for maintenance of skeletal integrity and proper utilization of calcium. Without vitamin D fortification of foods, such as milk, the dietary intake of vitamin D is small. Vitamin D deficiency in infants should not occur in the United States where dairy products are routinely fortified with vitamin D, and prenatal supplements are prescribed that generally contain vitamin D. Measurements of serum alkaline phosphatase have been useful in the investigation of certain bone diseases and as an indirect measure of vitamin D status. Serum levels of calcium, phosphate, and alkaline phosphatase are not reliable indicators of vitamin D deficiency. Osteocalcin levels correlated with lower serum levels of 25-hydroxyvitamin D and the higher parathyroid homone levels. The concentration of 1,25-dihydroxyvitamin D in serum is normally very low and hence its measurement requires a very sensitive analytical procedure.
