Growth response after administration of pharmacological doses of growth hormone in rats

Increased levels of endogenous growth hormone (GH) during childhood and adolescence result in a significant elevation of final height both in humans and in laboratory animals. We investigated the growth promoting effects of the administration of pharmacological doses of human GH (25 to 100 IU/kg/day) in 7 rats with severe intrauterine growth retardation (IUGR) due to artificially induced embryofetal alcohol syndrome (EFAS). Such doses of GH led to a marked growth spurt during the time of administration (14 days) exceeding the expected daily length and weight gain significantly, compared to placebo-treated EFAS litter and healthy controls (P less than 0.01, resp. P less than 0.05). This growth increment persisted in all treated animals throughout the total period of observation (250 days). Three out of the seven animals even showed incremental growth curves of both length and weight that stayed continuously within the +/- 2 standard deviation range of normally growing animals. Thus, it is shown for the first time that also exogenous GH administered temporarily at doses beyond the physiological level results in a significant elevation of final body size.