The use of a commercially available somatomedin-C radioimmunoassay in patients with disorders of growth

• Published in: The Journal of pediatrics Vol. 99; no. 5; p. 720
• Main Authors: Reiter, E O, Lovinger, R D
• Format: Journal Article
• Language: English
• Published: United States 01-11-1981
• Subjects: Adolescent; Child; Child, Preschool; Female; Growth Disorders - blood; Growth Disorders - physiopathology; Growth Hormone - metabolism; Humans; Hypothalamo-Hypophyseal System - physiopathology; Infant; Insulin-Like Growth Factor I; Male; Radioimmunoassay; Somatomedins - analysis
• ISSN: 0022-3476
• DOI: 10.1016/S0022-3476(81)80391-5

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.