FIG. 1.

Plasma prolactin response to exogenous tryptophan (120 mg/kg lean body weight) administered i.v. between 15 and 45 minutes. Among women (A), tryptophan appears to induce a greater plasma prolactin response in the CFS only group, and perhaps in CFS+FM group, than in the control group. There is no apparent difference among the men (B). All subjects exhibited a return to baseline concentration by 90-minutes postinfusion. Values are given as means ± SEM. CFS, chronic fatigue syndrome; FM, fibromyalgia.