Calcitriol deficiency in idiopathic juvenile osteoporosis.

Low plasma calcitriol (1,25-dihydroxycholecalciferol) and normal serum calcifediol (25-hydroxycholecalciferol) levels were noted during the evaluation of an 11-year-old girl with diffuse osteoporosis and pathologic fractures. The onset of osteoporosis prior to puberty and the characteristic metaphyseal location of the fractures supported the diagnosis of idiopathic juvenile osteoporosis (IJO). Treatment with calcitriol, 1.0 microgram daily, was associated with bone mineral accretion and a diminished incidence of fractures. Plasma calcitriol levels returned to normal when the disease resolved following puberty. This experience suggests a relationship between calcitriol deficiency and the pathogenesis of IJO.