Vitamin D and Genetics in Nutritional Rickets

Previous studies of Nigerian children with rickets demonstrated the superiority of calcium over vitamin D in producing healing. It is not known whether the addition of vitamin D to calcium will produce a better response to treatment than calcium alone in Nigerian children. A previous study suggested the possibility that vitamin D may augment the effect of calcium. We will compare the response of rickets to calcium with and without vitamin D. In addition, very little human data clearly demonstrates the effect of supplemental vitamin D on calcium absorption. We will assess whether oral vitamin D increases the already high calcium absorption even further.

Recent published data indicate that the increase in serum 25-hydroxyvitamin D may be more sustained with vitamin D3 than with vitamin D2. We will compare the response of Nigerian children with and without rickets to orally administered vitamin D3 and vitamin D2.

Because nutritional rickets tends to run in families, we will also examine amplified DNA for evidence of mutations that influence calcium and vitamin D metabolism among families of children with rickets in Nigeria and Bangladesh. Families possessing a recently identified 25-hydroxylase mutation will be given oral vitamin D2 and vitamin D3 to determine the functional status of the 25-hydroxylase enzyme.