title: Function of the GH/IGF-1 axis in healthy middle-aged male runners.
abstract: In an attempt to examine the effect of prolonged physical activity on the function of the GH/IGF-1 axis during the aging process in man, we have evaluated basal and GHRH (GHRH-29: 1 microgram/kg i.v. as a bolus) stimulated GH secretion as well as basal plasma IGF-1 levels in a group of 25 healthy runners (50-60 years, mean age 55.5 +/- 0.6) and 24 age-matched relatively sedentary normal controls (mean age 55.8 +/- 0.7). The runners had a minimum distance in kilometers of 26 km/week for at least 15 years, and competed in distances ranging from 16 km to the marathon. In runners, GHRH induced an increase of GH which was significantly higher (p < 0.001) than that observed in the age-matched controls. Baseline IGF-1 levels were significantly higher (p < 0.001) in trained runners (171 +/- 8.4 micrograms/1) compared to the controls (91.1 +/- 5.5 micrograms/1). These data show that in middle-age prolonged physical activity increases the function of the GH/IGF-1 axis. To clarify the possible mechanisms underlying the GH/IGF-1 secretory pattern in the runners, the GH responses to both single and combined administration of GHRH and arginine (ARG: 30 g infused over 30 min), a GH secretagogue likely acting via inhibition of hypothalamic somatostatin release, were investigated in 6 runners (mean age 55 +/- 1.9 years) and 6 controls (mean age 55 +/- 0.9 years). ARG clearly increased the GH response to GHRH in the controls, whereas it was unable to further potentiate the GH-releasing effect of GHRH in runners, thus suggesting that the increased GH responsiveness to GHRH might be due to an exercise-related decrease in endogenous hypothalamic somatostatinergic activity.
authors.affiliation: Chair of Endocrinology, University of Ferrara, Italy.
authors.forename: M R
authors.initials: MR
authors.lastname: Ambrosio
authors.forename: A
authors.initials: A
authors.lastname: Valentini
authors.forename: G
authors.initials: G
authors.lastname: Trasforini
authors.forename: F
authors.initials: F
authors.lastname: Minuto
authors.forename: E
authors.initials: E
authors.lastname: Ghigo
authors.forename: S
authors.initials: S
authors.lastname: Cella
authors.forename: A
authors.initials: A
authors.lastname: Margutti
authors.forename: R
authors.initials: R
authors.lastname: Pansini
authors.forename: E C
authors.initials: EC
authors.lastname: degli Uberti
mesh_terms: D000375:Aging / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone