Growth hormone (GH) influences not only skeletal growth and maturation but also bone turnover and mineral deposition. The effect on bone mineral status of 2 different regimens of rhGH therapy was evaluated in 22 children with idiopathic GH deficiency (GHD) - age 5-8 yrs; bone age 3-5 yrs. Ten of them (group 1) were treated 3 times a week with rhGH, administered subcutaneously, for a total weekly dose of 0.5 IU/kg and 12 (group 2) with the same weekly dose 6 times per week. Insulin-like growth factor 1 (IGF-1) and osteocalcin (OC) levels increased in both groups after therapy but they were higher in group 2. In basal conditions bone mineral content (BMC) and BMC/bone width ratio (determined by dual image-assisted photon absorptiometry) were significantly lower in patients than in controls and significantly increased after 6 months of rhGH therapy only in patients of group 2. rhGH administered 3 times a week increased IGF-1 and OC levels, indicating that turnover and remodeling processes of the bone had started, but the same dose had to be given every day to lead to calcium deposition in the bones. Probably a continuous supply of rhGH better optimizes the body utilization of the hormone, as indicated by better height velocity and bone density in patients of group 2. The response to an acute load of 1,25(OH)2D3 (1.5 micrograms/day for 4 days), both before and after a month of rhGH therapy (weekly dose of 0.5 IU/kg 6 times were week), was evaluated in 16 children with GHD - age 6-9 yrs.(ABSTRACT TRUNCATED AT 250 WORDS)