Insulin-like growth factor 1 (IGF-1): a growth hormone

Aim-To contribute to the debate about whether growth hormone (GH) and insul in-like growth factor 1 (IGF-1) act independently on the growth process. Methods-To describe growth in human and animal models of isolated IGF-1 def iciency (IGHD), such as in Laron syndrome (LS; primary IGF-1 deficiency and GH resistance) and IGF-1 gene or GH receptor gene knockout (KO) mice. Results-Since the description of LS in 1966, 51 patients were followed, man y since infancy. Newborns with LS are shorter (42-47 cm) than healthy babie s (49-52 cm), suggesting that IGF-1 has some influence on intrauterine grow th. Newborn mice with IGF-1 gene KO a 30% smaller. The postnatal growth rat e patients with LS is very slow, the distance from the lowest normal centil e increasing progressively. If untreated, the final height is 100-136 cm fo r female and 109-138 cm for male patients. They have acromicia, organomicri a including the brain, heart, gonads, genitalia, and retardation of skeleta l maturation. The availability of biosynthetic IGF-1 since 1988 has enabled it to be administered to children with LS. It accelerated linear growth ra tes to 8-9 cm in the first year of treatment, compared with 10-12 cm/year d uring GH treatment of IGHD. The growth rate in following years was 5-6.5 cm /year. Conclusion-IGF-1 is an important growth hormone, mediating the protein anab olic and linear growth promoting effect of pituitary GH. It has a GH indepe ndent growth stimulating effect, which with respect to cartilage cells is p ossibly optimised by the synergistic action with GH.