FUNCTION OF GH IGF-I AXIS IN AGING - MULTICENTER STUDY IN 152 HEALTHYELDERLY SUBJECTS WITH DIFFERENT DEGREES OF PHYSICAL-ACTIVITY/

We evaluated somatotropic function in 142 healthy elderly subjects (54 men and 88 women), aged 60-90 years and in 10 non-professional, but r egularly training elderly distance runners (7 men and 3 women), aged 6 0-71 years. In the healthy elderly, basal plasma growth hormone (GH) a nd insulin-like growth factor-I (IGF-I) median levels were 0.6 mu g/L (25th and 75th centiles = 0.3, 1.3) and 100.5 mu g/L (25th and 75th ce ntiles = 63, 140), respectively. About 53% of the elderly had plasma I GF-I levels within the 3rd-97th centiles of young-adult subjects. Basa l GH and IGF-I were not correlated with each other nor, with the degre e of physical activity, evaluated by a self-administered questionnaire : however, basal GH showed a very weak positive correlation with age w hile IGF-I showed a highly significant negative correlation. The peak GH response to GHRH (1 mu g/kg, iv), did not correlate with age, BMI a nd physical activity in 87/142 subjects investigated, but was highly c orrelated with basal GH levels. Correlation coefficients of plasma gro wth hormone binding protein (GHBP) with basal GH levels and peak GH le vels following GHRH were r=-0.29 and r=-0.36, respectively, but statis tical significance was not reached. In the ''runners'', median values of both basal and GHRH-induced GH peak were higher than those recorded in the healthy elderly, but IGF-I levels were not significantly diffe rent and they too declined with age. These data suggest that: 1) plasm a IGF-I rather than basal or stimulated GH is a better index for evalu ating the effect of aging on the GH/IGF system; 2) while usual physica l activity in itself does not influence somatotropic Junction, enduran ce training is related to higher basal GH levels, but fails to oppose the age-related decline of plasma IGF-I levels. (C) 1997, Editrice Kur tis.