1999 Clinical and Scientific Meeting

Dr R. Burnet, Prof. G. Scroop, Dr B. Chatterton, Dr Bu Yeap

Endocrine Unit,
Royal Adelaide Hospital,
North Terrace,
Adelaide SA 5000

Serum Potassium and Hormone Responses to Exercises in Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) is characterised by long standing debilitating fatigue, the pathophysiology of which remains undefined.

The effects of exercise on the hypothalamic-pituitary-adrenal axis, growth hormone, prolactin and plasma electrolytes in patients and healthy matched controls were studied. Subjects were each exercised for 10 minutes on a cycle ergometer at a work load of 75% maximal oxygen consumption.

Serial measurements were taken at one minute intervals for 10 minutes and 5 minutes thereafter for 70 minutes for plasma ACTH, growth hormone, prolactin, cortisol, sodium, potassium and bicarbonate ate rest, during exercise and recovery.

Resting values for serum electrolytes, growth hormone, prolactin and cortisol was similar in both groups.

A significant increase in the levels of ACTH was noted at rest in CFS subjects. During exercise the mean increase in ACTH in CFS was 86.6 ng/L compared to 54.6 ng/L in controls and although cortisol's values increased in both groups, the difference was nonsignificant. Maximum increase in potassium with exercise in CFS was 0.63 mmol/L and 0.98 mmol/L in controls (p=0.013). Plasma bicarbonate decreased by a mean of 9.5mmols/L in CFS and 8.5 mmol/L in controls (p > 0.05). The response to exercise of growth hormone and prolactin was similar in controls and CFS subjects.

These findings suggest an abnormal potassium response to exercise in CFS subjects. This decrease in potassium levels indicates either an abnormal and reduced flux of potassium across the cell membrane with exercise or a decrease in the total body potassium (TBK). Other studies have shown a decrease in the TBK, so this abnormal potassium response is likely to be due to a total body potassium deficiency.

There is no abnormality of the pituitary hormonal response in CFS subjects to exercise, but a diminished adrenal response to ACTH as seen in persons with any chronic debilitating illness.


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