The interrelationships between serum 25-hydroxycholecalciferol, serum parathyroid hormone and bone changes in anticonvulsant osteomalacia.

Serum 25-hydroxycholecalciferol (25-HCC) and serum parathyroid hormone (iPTH) were measured in 59 randomly selected adult epileptic outpatients receiving chronic anticonvulsant therapy. Quantitative morphometric analysis of iliac crest biopsies was performed. A mild degree of osteomalacia was found which was inversely correlated to dietary vitamin D intake. Serum 25-HCC was reduced in the epileptic patients compared to a control group, although dietary intake of vitamin D was higher than the mean daily intake in the Danish population. Serum 25-HCC was positively correlated to dietary vitamin D intake, but not correlated to the severity of bone changes, indicating that other factors than circulating 25-HCC are responsible for the development of anticonvulsant osteomalacia. Serum 25-HCG was inversely correlated to serum iPTH in patients with a low dietary calcium intake. The mean value of serum iPTH was not increased, and there was no correlation between serum iPTH and bone morphometry.