A combination of 6 months of treatment with pyridostigmine and triweekly exercise fails to improve insulin-like growth factor-I levels in fibromyalgia, despite improvement in the acute growth hormone response to exercise

Objective. People with fibromyalgia (FM) often have low insulin-like growth factor-I (IGF-I) levels and a suboptimal growth hormone (GH) response to acute exercise. As previous work had demonstrated a normalization of the acute GH response to exercise with the use of pyridostigmine (PYD), we tested the hypothesis that 6 months of PYD therapy plus supervised exercise would increase IGF-I levels. Methods. Subjects with primary FM were randomized into 4 groups: (1) PYD/exercise; (2) PYD/diet recall; (3) placebo/exercise; and (4) placebo/diet recall. The dosing of PYD was 60 mg tid for 6 months. Resting IGF-I levels were measured at baseline and after 6 months of treatment. In addition the acute GH response to exercise at VO₂ max was measured at baseline and after treatment. Results. A total of 165 FM subjects (mean age 49.5 yrs, 5 male) were entered and 154 (93.3%) completed the study. Six months of therapy (PYD plus exercise or exercise alone) failed to improve the IGF-I levels. The use of PYD 1 hour prior to exercise improved the acute GH response (4.54 ng/dl) compared to placebo (1.74 ng/dl) (p = 0.001) at the end of the 6-month trial. The acute GH response to exercise at baseline did not correlate with IGF-I, age, depression, medications, estrogen status, or obesity. Conclusion. A combination of triweekly supervised exercise plus the daily use of PYD for 6 months failed to increase IGF-I levels in patients with FM, despite the confirmation that PYD normalizes the acute GH response to strenuous aerobic exercise.