Endocrine Abstracts

Background: Diabetes increases the risk of developing coronary heart disease irrespective of glycaemic control. Cortisol and growth hormone (GH) abnormalities have been found in these patients and have been proposed as possible mechanisms for this increased risk.
Regular exercise, through an unknown mechanism, can modify cardiovascular risk and so prevent or delay the progression of coronary heart disease. In this study we assessed whether an exercise program would alter the secretion and activity of cortisol and growth hormone in individuals with diabetes.
Methods: 18 male patients with diabetes attended a twice weekly hour long supervised exercise class for 12 weeks. An integrated assessment of cortisol and GH secretion and action was performed before and after the program.
Results: Data are mean +/- SD. Age was 54 (33-71). The exercise program significantly improved mean blood pressure (106 +/- 11 v 98 +/- 10, p<0.001), and HDL/cholesterol ratio (4.7 +/- 1.5 v 4 +/- 1.6, p<0.05).
24 hour urinary GH secretion showed a trend to decrease (6.2 +/- 5 v 4.8 +/- 5.3, p=0.06) but 9am GH did not change. 24 hour urinary cortisol secretion, 9am fasting cortisol, and diurnal salivary cortisol were unaffected by exercise. Suppression of the HPA axis (0.25mg dexamethasone) was not altered (270 +/- 119 v 306 +/- 127, p=0.31) although the axis became more sensitive to stimulation (cortisol response to a standard exercise regime) following the exercise program (-7.6 +/- 10 v 11.6 +/- 12, p<0.001). Peripheral cortisol sensitivity (skin blanching to topical beclomethasone) decreased following exercise (8 +/- 4 v 6 +/-3, p<0.05).
Conclusions: Regular exercise affects certain aspects of pituitary function, reducing GH secretion and increasing tonicity of the HPA axis. Further investigation of the role played by exercise on these hormone axes is required.