Quantitation of urinary somatomedin-C in children with normal and abnormal growth.
The renal excretion of radioimmunoassayable somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) was measured in 12-h overnight urine samples obtained from 88 subjects, aged 3-19 yr. The participants included 34 healthy children (group 1), 29 children with idiopathic growth failure and normal GH stimulation tests (group 2), and 25 GH-deficient subjects (group 3). The mean (+/- SEM) urinary Sm-C/IGF-I excretion in group 1 (28.4 +/- 2.1 mU/kg) was significantly greater than that in group 2 (8.1 +/- 1.6 mU/kg) or group 3 (8.6 +/- 1.3 mU/kg). Twenty-two of the 29 subjects in group 2 had urinary Sm-C/IGF-I values less than 8 mU/kg. After the administration of biosynthetic GH to 12 GH-deficient subjects, urinary Sm-C/IGF-I excretion rose from 10.3 +/- 2.3 to 21.4 +/- 4.2 mU/kg within 12 h (P less than 0.05), indicating that renal excretion of Sm-C/IGF-I is GH dependent. One woman with acromegaly had markedly elevated urinary Sm-C/IGF-I excretion (420 mU/kg). The authenticity of urinary Sm-C/IGF-I was confirmed by high pressure liquid chromatography (HPLC). Assay of serial dilutions of urinary Sm-C/IGF-I demonstrated a direct proportionality between concentration and dilution. Although it is not possible to identify whether urinary Sm-C/IGF-I reflects local or generalized synthesis of the peptide, we hypothesize that quantitation of Sm-C/IGF-I in timed urine collections will yield additional information about GH production and action in children with normal and abnormal growth.
Quattrin
T
T
Department of Pediatrics, Children's Hospital of Buffalo, New York 14222.
Albini
C H
CH
Vandlen
R L
RL
MacGillivray
M H
MH
D000293:Adolescent; D000328:Adult; D001827:Body Height; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006130:Growth Disorders / Q000652:urine*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000652:urine*; D008297:Male; D011627:Puberty; D013002:Somatomedins / Q000652:urine*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I