Insulin‐like Growth Factor I (Igf‐i) in Healthy Children, Adolescents and Adults as Determined by a Radioimmunoassay Specific for the Synthetic 53–70 Peptide Region

Abstract

A radioimmunoassay (RIA) specific for the synthetic 53-70 peptide region of human insulin-like growth factor I (IGF-I) was used to determine IGF-I in the serum of 191 healthy newborns, children and adolescents and in 26 adults. The results compare favourably with reported values obtained using RIA systems for the native IGF-I molecule. Intra- and inter-assay CV were 3.3 and 7.2% respectively. In childhood, mean +/- SD IGF-I levels rise from 6.0 +/- 3.5 nmol/l in newborns to 16.5 +/- 4.0 nmol/l at 8-11 years in both sexes. At the onset of puberty, IGF-I levels in females (24.9 +/- 6.6 nmol/l) are significantly (P greater than 0.005) higher than in males (17.2 +/- 4.2 nmol/l). With further pubertal development IGF-I levels continue to rise, reaching peak values at pubertal stage P4 (40.6 +/- 4.5 nmol/l in males, 42.8 +/- 5.1 nmol/l in females) and decline thereafter to lower values during adulthood: 16.5 +/- 5.8 nmol/l (males) and 24.2 +/- 7.0 nmol/l (females) (P greater than 0.001). In pubertal males, IGF-I correlates significantly with height (r = 0.66, P less than 0.001), bone age (r = 0.69, P less than 0.001) and growth velocity (r = 0.64, P = 0.025) as well as with testosterone levels (r = 0.69, P less than 0.001). In pubertal females a significant correlation is found between IGF-I and height (r = 0.55, P less than 0.020). The ready availability of a simple, precise and reproducible IGF-I RIA, should contribute much to evaluating the importance of IGF-I measurements in normal growth and in the diagnosis and therapy of various growth disorders.

Serum Insulin-like Growth Factor I (Somatomedin-C) Level in Normal Subjects from Infancy to Adulthood, Pituitary Dwarfs and Normal Variant Short Children.

“…Many reports on the age-dependent change in the acid extracted IGF-I levels in children have been published (Daughaday et al, 1987 b;Luna et al, 1983;Zapf et al, 1981;Silbergeld et al, 1986;Bala et al, 1981 andRosenfeld et al, 1986) (Zapf et al 1981;Kemp et al;Bala et al, 1981;Rosenfeld et al, 1986;Merimee et al, 1982 andBinoux et al, 1986) and also in native plasma (Furlanetto et al, 1977;Reiter et al, 1981;Underwood et al, 1981;and Rubin et al, 1986). However, extensive overlap existed among normal deficiency and normal variant short children.…”

Role of oestrogen in the regulation of bone turnover at the menarche

“…There are increases in IGF-I during childhood (Fig. 3), with peak levels during pubertal development in boys and girls (Luna et al 1983, Silbergeld et al 1986, Cara et al 1987, Johansen et al 1988, Costin et al 1989, Argente et al 1993, Blumsohn et al 1994, Moreira-Andres et al 1995, Sabatier et al 1996, Cadogan et al 1998, Libanati et al 1999, and correlation with height velocity (Silbergeld et al 1986, Juul et al 1994. These studies also report that IGF-I correlates better with Tanner stage than with chronological age.…”

Pubertal Growth Spurt Induced by Human Chorionic Gonadotropin in Hypogonadotropic Growth Hormone-Deficient Children.

“…And nocturnal HGH secretion is also increased after the onset of puberty (Parker et al, 1984;Link et al, 1986). The somatomedin C concentration during puberty has been shown to be higher than in the prepubertal stage (Luna et al, 1984;Rosenfield et al, 1984;Silbergeld et al, 1986;Cara, I. F., 1987). In view of this evidence, it was generally accepted that the pubertal growth spurt in normal children was produced by increased HGH secretion followed by an increase in Somatomedin C.…”

“…However, the pubertal stage when the somatomedin C (IGF-I) concentration is at its highest does not always correspond to peak growth (Silbergeld, et al, 1986). Exogenous testosterone does not increase somatomedin C in hypogonadotropic GH-deficient children receiving or not receiving human growth hormone (HGH) (Craft and Underwood, 1984;Parker et al, 1986).…”