EFFECTS OF 1,25-DIHYDROXYVITAMIN-D(3) AND GROWTH-HORMONE THERAPY ON SERUM OSTEOCALCIN LEVELS IN CHILDREN WITH GROWTH-HORMONE DEFICIENCY

In order to investigate the influence on bone metabolism of growth hor mone (GH), we evaluated the response to an acute load of 1,25(OH)2D3 ( Rocaltrol(R)) (1.5 mug/day for 4 days) in 16 growth hormone-deficient prepubertal children (11 boys and 5 girls, aged from 6.2 to 9.6 years) both before and after 1 month of human GH (hGH) therapy (0.1 IU/kg/da y, 6 times per week). Before and after the 1,25(OH)2D3 load, serum IGF -I, osteocalcin, Ca, P, alkaline phosphatase (ALP) and urinary excreti on of Ca and P were measured. The serum levels of osteocalcin rose sig nificantly after the first 1,25(OH)2D3 load, without an increase in IG F-I values and with a slight non-significant increase in serum Ca and P. Almost superimposable increases of osteocalcin, Ca and P were obser ved after 1 month of hGH therapy, with a significant increase of IGF-I , but they did not rise further after the second 1,25(OH)2D3 load. On the basis of our results, 1,25(OH)2D3 seems to have a stimulatory acti on on osteoblastic activity even in the absence of normal levels of GH . However, there is no apparent additional stimulatory activity after administration of hGH. Osteocalcin level behaviour during our study mi ght suggest that GH and 1,25(OH)2D3 have a common and easily saturable stimulatory pathway on osteoblastic function.