Hypothalamic-pituitary-insulin-like growth factor-I axis dysfunction in patients with fibromyalgia (FM)

OBJECTIVE: To investigate the serum levels of insulin-like growth

factor-I (IGF-I) in patients with fibromyalgia (FM) compared

to healthy controls and patients with other rheumatic

diseases, and to explore possible etiologic mechanisms of low

IGF-I levels in patients with FM.

METHODS: Five hundred

patients with FM and 152 controls (74 healthy blood donors, 26

myofascial pain patients and 52 patients with other rheumatic

diseases) were studied. All had measurements of acid extracted

serum IGF-I. A subset of 90 patients with FM were evaluated

for clinical features that might explain low IGF-I levels.

Twenty-five patients with FM underwent growth hormone (GH)

provocation testing with l-dopa and clonidine.


mean serum IGF-I level in patients with FM was 138 +/- 56

ng/ml and in controls 215 +/- 86 ng/ml (p = 0.00000000001).

Low levels of IGF-I were not due to depression, tricyclic

medications, nonsteroidal antiinflammatory drugs, poor aerobic

conditioning, obesity, or pain level. Patients with focal

myofascial pain syndromes had normal IGF-I levels (236 +/-

68), as did most patients with other rheumatic disorders,

unless they had concomitant FM. Patients with FM with

initially normal levels often had a rapid decline of IGF-I

over 1 to 2 years. Most patients with FM with low IGF-I levels

failed to secrete GH after stimulation with clonidine and


CONCLUSION: Many, but not all, patients with FM have

low levels of IGF-I that cannot be explained by clinical

associations. These results suggest that low IGF-I levels in

patients with FM are a secondary phenomenon due to

hypothalamic-pituitary-GH axis dysfunction.

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