title: The use of a commercially available somatomedin-C radioimmunoassay in patients with disorders of growth.
abstract: Somatomedin-C concentrations were measured by a newly available commercial radioimmunoassay in plasma samples from 41 children undergoing clinical evaluation of hypothalamic-pituitary function because of varied disorders of growth. Sequential Sm-C levels were stable; the coefficient of variation remained below 10% over a three-hour period. The Sm-C values of 27% of the children were discordant with the GH responses; of 25 patients with normal provoked-GH levels, seven had low Sm-C values, whereas four of 16 patients with inadequate GH responses had normal Sm-C concentrations. All of the discordant data occurred in 31 patients with diminished linear growth velocity. More patients with decreased growth velocity had diminished Sm-C levels than did short children with normal linear growth velocity. These data suggest that many variables, in addition to adequacy of GH production and plasma Sm-C levels, may affect net Sm-C activity. This possibly reduces the usefulness of the Sm-C radioimmunoassay as a single screening test for abnormalities of GH secretion.
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006130:Growth Disorders / Q000097:blood* / Q000503:physiopathology; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology; D007223:Infant; D007334:Insulin-Like Growth Factor I; D008297:Male; D011863:Radioimmunoassay; D013002:Somatomedins / Q000032:analysis*
chemical_list: D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone