Acid-labile subunit (ALS) measurements in children.

Almost all of the serum IGFs are found in a ternary complex composed of IGF, IGFBP-3 and acid-labile subunit (ALS). It was reported that ALS levels were age- and sex-dependent. In the present study we measured serum ALS levels in 264 normal children (145 boys and 119 girls) aged from 5 days to 16 years, and 15 patients with growth hormone deficiency (GHD) aged from 11 months to 13 years. Serum ALS levels increased during childhood, and reached peak values in mid to late puberty. ALS levels reached their highest levels 2 years earlier in girls than in boys. Serum ALS levels were significantly correlated with serum IGF-I levels and IGFBP-3 levels. Serum ALS levels were below -2SD in 6 out of 7 children with complete GHD (CGHD), while serum ALS levels were below -2SD in 1 out of 8 patients with partial GHD (PGHD). These results indicate that serum ALS levels are regulated by GH, and that the measurement of ALS is useful for the diagnosis of CGHD in children.