Calcium metabolism in bone disease: effects of treatment with microcrystalline calcium hydroxyapatite compound and dihydrotachysterol.

Microcrystalline calcium hydroxyapatite compound (MCHC) was given orally together with small doses of dihydrotachysterol (DHT) to a number of patients with osteogenesis imperfecta (OI). Serial calcium and phosphate balances in three patients representing wide variations in severity of OI are presented over periods from eight months to two years. The combination of MCHC and DHT resulted in an immediate positive calcium balance which was maintained throughout the period of assessment in 2 cases. However, no radiological improvement could be demonstrated. Substituting calcium gluconate for MCHC resulted in a reduction of positive balance. No adverse effects were noted. The reasons why MCHC with DHT should result in increased calcium retention are discussed. This combination of MCHC and DHT could be of benefit in many common situations of bone demineralization, such as osteoporosis.