To determine activity of the growth hormone-insulin-like growth factor-1 (GH-IGF-1) axis in women with fibromyalgia (FM).
Premenopausal women with FM (n = 24) and premenopausal healthy women (n = 27) were studied. IGF-1 was measured in 23 patients with FM and 25 controls. GH was measured during a stepped hypoglycemic hyperinsulinemic clamp procedure (blood glucose decreased from 90 to 40 mg/dl every 30 min in 10 mg/dl decrements) in 12 FM and 13 control subjects.
IGF-1 concentrations were similar in the FM (200 +/- 71 ng/ml, mean +/- SD) and control (184 +/- 70 ng/ml) groups. By multiple variable analysis, IGF-1 was negatively associated with age (p = 0.0006), body mass index (BMI) (p = 0.006), and 24 h urinary free cortisol (p = 0.007) in healthy controls. Even after accounting for these factors, there was no association between FM and IGF-1. The average peak GH achieved during hypoglycemia was lower in patients with FM (range 5 to 58 ng/ml, median 13 ng/ml) versus controls (6 to 68 ng/ml, median 21 ng/ml) (p = 0.04). However, BMI was a significant predictor of average peak GH in FM (r = -0.62, p < 0.01) and control subjects (r = -0.40, p = 0.06). After considering BMI, there was no significant association between FM subjects and the average peak GH (p = 0.20).
In this sample of premenopausal women with FM, the activity of the GH-IGF-1 axis was similar to that of healthy controls. Increases in age and obesity were both strongly associated with lower activity of this axis, suggesting that these factors must be considered when studying activity of the GH-IGF-1 axis in FM.