Age-Related Decrease Hormone-Releasing

in Plasma Growth Hormone: Response to Growth Hormone, Arginine, and L-Dopa in Obesity

Katsuaki Tanaka, Shuji Inoue, Junko Shiraki, Toshihiro Shishido, Mari Saito, Kazushi Numata, and Yutaro Takamura Aging is associated with a reduction in plasma growth hormone (GH) secretion in non-obese subjects. To determine whether or not age-related changes in plasma GH secretion exist in obese subjects, we measured (a) plasma GH response to growth hormone-releasing hormone (GRH; 1 pg/ kg body wt), arginine (0.5 gl kg body wt), L-dopa (500 mg], and (b) plasma glucose, insulin, and free fatty acids (FFAs) in 26 fasted obese subjects of various ages ranging from 16 to 71 years. Only subjects with a body mass index (BMI; kg/m’) between 30.0 and 39.0 were studied. Six subjects were adolescents, 9 were in their 2Os, and 11 were 30 years or older. The mean peak levels of plasma GH in response to GRH, arginine, and L-dopa in obese subjects were 11.3 ? 2.1, 21.9 2 4.4, and 5.2 rf: 0.3 ng/mL in adolescents, 8.2 2 1.6, 9.1 + 1.5, and 3.1 2 0.6 ng/mL in those in their 2Os, and 4.5 2 0.4,7.3 rt 1.4, and 2.8 ‘_ 0.3 ng/mL in those 30 years or older, respectively, showing a significant decrease in peak GH level with advancing age (P < .05 to P < .Ol). There was a negative correlation between the logarithmic increase in age and the peak GH response to GRH (I = -.635, P < .Ol), arginine (r = -.564, P < .Ol), and L -dopa (r = -.630, P < .Ol), and between the logarithmic increase in age and the integrated GH response to GRH (r = -.564, P

Age-related decrease in plasma growth hormone: response to growth hormone-releasing hormone, arginine, and L-dopa in obesity.

Aging is associated with a reduction in plasma growth hormone (GH) secretion in non-obese subjects. To determine whether or not age-related changes in...
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