It has been known for 25 years that FM patients have an abnormal sleep pattern involving stages 3 and 4 of non REM sleep. As GH is secreted predominantly during stages 3 and 4 of non-REM sleep, it was originally hypothesized that FM patients may have impaired GH secretion. IGF-1 levels are abnormally low in some fibromyalgiapatients. In an analysis of IGF-1 levels in 500 female FM patients and 152 age matched non-FM subjects the mean IGF-1 level in the FM patients was 137±58 ng/ml versus 216±86 ng/ml in controls. Eighty-five percent of the FM patients had IGF-1 levels below the 50th percentile of the control population and 56% fell below the 20th percentile.
Growth hormone deficiency in adults has been associated with many symptoms that are similar to those described by FM patients: low energy, poor general health, reduced exercise capacity, muscle weakness, cold intolerance, impaired cognition, dysthymia and decreased lean body mass. IGF1 levels are often found to be low in FM patients. The few studies done so far have found symptomatic improvement of CFS and FM patients with GH injections.
It is likely that the problem in FM is a physiologic GH deficiency. Evidence was provided by a study in which FM patients were exercised to voluntary exhaustion on a treadmill; this is a standard test of GH secretion. Unlike healthy controls, FM patients were unable to mount a GH response to exercise, despite reaching an anaerobic threshold (an indication of an adequate exercise workload). However, when fibromyalgia patients were given pyridostigmine 1 hour prior to exercising, they were able to mount a reasonable GH response. As pyridostigmine is known to reduce somatostatin tone in the hypothalamus, this result is compatible with the notion that GH deficiency in fibromyalgia is a potentially reversible problem that has a physiologic basis i.e. increased hypothalamic somatostatin tone. [Eduardo S. Paiva, Atul Deodhar, Kim D. Jones, Robert Bennett; Oregon Health Sciences University, Portland (press release).
