Doctoral Dissertations

Date of Award

5-2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

Dixie L. Thompson

Committee Members

Edward T. Howley, David R. Bassett Jr., Eugene C. Fitzhugh

Abstract

Growth hormone (GH) is one of several hormones known to decrease with age. Low GH levels may be linked with various disease conditions because of its stimulatory role in muscle and bone maintenance, and lipolysis. Growth hormone is associated with insulin, glucose, and estrogen levels, and GH is greatly reduced following menopause. It has been established that obesity is inversely related to low GH levels and positively associated with insulin resistance and dyslipidemia. Exercise is a potent stimulator of GH secretion and the GH response to exercise is attenuated with obesity. The purpose of this study was to evaluate the effect of body composition on the GH response to exercise in postmenopausal women and how the response was related to insulin, glucose, and estradiol concentrations. To do this, 9 obese and 10 non-obese apparently healthy postmenopausal women (mean age ± SE; 56.3 ± 0.9 y) engaged in 30 minutes of treadmill exercise at 70% of their predetermined VO2max. Blood samples were collected periodically during pre-exercise, exercise, and recovery periods for the determination of GH, insulin, glucose, glycerol, and estradiol concentrations. The results of this study indicate that a 30-minute bout of treadmill exercise at 70% of VO2max sufficient to elicit a significant elevation of serum GH concentrations in untrained obese and non-obese postmenopausal women and that the GH response to exercise is negatively related to body weight and body fat. However, the large variance in the GH response made it impossible to demonstrate statistically, significant group differences.

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