Near-normal linear growth in the setting of markedly reduced growth hormone and IGF-1. A case report.
A 14.2-year-old prepubertal boy diagnosed with complete-type growth hormone deficiency and tertiary hypothyroidism, keeps growing in the height range between -1 and -2 SD. He has been treated with levothyroxine only. To understand the growth mechanism of this boy, we analyzed the serum growth hormone (GH) with a radioimmunoassay (RIA), serum GH bioactivity with Nb2 and erythroid progenitor cell bioassays, and growth hormone-binding protein (GHBP) with a ligand-mediated immunofunctional assay (LIFA). In addition, IGF-1 and free IGF-1 were analyzed by immunoradiometric assay (IRMA) and insulin-like growth factor-binding protein-3 (IGFBP-3) by Western immunoblot. Peak GH-RIA responses to insulin, arginine and GH-releasing factor, and nocturnal GH secretion, were low (0.5-2.3 ng/ml); bioactive GH was low (0.313 ng/ml), and GHBP was elevated (84 ng/ml). The serum levels of IGF-1 and free IGF-1 were continuously low, 17.1-39.3 and 0.17-0.26 ng/ml, respectively. Moreover, serum IGFBP-3 levels were low (1.68- 1.39 mg/l) and IGFBP-3 protease activity was negative. Prolactin and insulin were in the normal range. The result of the assay for growth-promoting activity showed that the patient's serum stimulated normal erythroid progenitor cells twice as potently as did healthy thin adult control serum. These results suggest that GH and IGF-1 are not indispensable for maintaining physical growth in this boy. Thus, it appears that circulating GH and IGF-1 are not mandatory requirements for maintaining normal physical growth, and other, as yet uncharacterized, pathways or growth factors might be sufficiently compensatory under certain conditions.
Murashita
M
M
Department of Pediatrics, Hokkaido University School of Medicine, Sapporo, Japan.
Tajima
T
T
Nakae
J
J
Shinohara
N
N
Geffner
M E
ME
Fujieda
K
K
D000293:Adolescent; D001790:Blood Physiological Phenomena; D001827:Body Height; D001835:Body Weight; D003114:Colony-Forming Units Assay; D015672:Erythroid Precursor Cells / Q000166:cytology; D019382:Human Growth Hormone / Q000172:deficiency*; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000172:deficiency; D007334:Insulin-Like Growth Factor I / Q000172:deficiency*; D008297:Male; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use
D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013974:Thyroxine