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Tryptophan depletion in Chronic Fatigue Syndrome, a pilot cross-over study

Tuesday 23 September 2014


From ProHealth:



Tryptophan depletion in chronic fatigue syndrome, a pilot cross-over study

By K.H. Gerard et al.
September 22, 2014

By K.H. Gerard et al.

Editor’s comment: The authors proposed that people with ME/CFS have excessive amounts of serotonin, leading to exhaustion, depression, and cognitive problems. They tested their hypothesis by blocking 5-HT3 (serotonin) receptors using ondansetron (Zofran), an anti-nausea drug. No improvement was seen.


Background: Chronic fatigue syndrome (CFS) is still an enigmatic disorder. CFS can be regarded as a complex disorder with tremendous impact on lives of CFS-patients. Full recovery without treatment is rare.

A somatic explanation for the fatigue is lacking. There is clinical and experimental evidence implicating enhanced serotonergic neurotransmission in CFS. Genetic studies and imaging studies support the hypothesis of upregulated serotonin system in CFS.

In line with the hypothesis of an increased serotonergic state in CFS, we performed a randomised clinical trial investigated the effect of 5-HT3 receptor antagonism in CFS. No benefit was found of the 5-HT3 receptor antagonist ondansetron compared to placebo.

To further investigate the involvement of serotonin in CFS we performed a placebo controlled cross over pilot study investigating the effect of Acute Tryptophan Depletion.

Findings: Five female CFS-patients who met the US Center[s] for Disease Control and Prevention criteria for CFS were recruited. There were two test days, one week apart. Each participant received placebo and ATD. To evaluate the efficacy of the ATD procedure tryptophan and the large neutral amino acids were measured. The outcome measures were fatigue severity, concentration and mood states.

ATD resulted in a significant plasma tryptophan to large neutral amino acid ratio reduction of 96%. There were no significant differences in fatigue-, depression and concentration between the placebo- and ATD condition.

Conclusions: These first five CFS-patients did not respond to the ATD procedure. However, a much larger sample size is needed to draw final conclusions on the hypothesis of an increased serotonergic state in the pathophysiology of CFS.

Source: Gerard KH The, Robbert J Verkes, Durk Fekkes, Gijs Bleijenberg, Jos WM van der Meer and Jan K Buitelaar Tryptophan depletion in chronic fatigue syndrome, a pilot cross-over study BMC Research Notes 2014, 7:650 Published: 16 September 2014 doi:10.1186/1756-0500-7-650


The above originally appeared here.



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