Growth hormone appears to relieve the pain associated with fibromyalgia, a new study shows.

"GH might be useful in treating patients that are not GH-deficient, but convincing the regulatory authorities to approve that new indication will require deeper study," said Dr. Guillem Cuatrecasas, who led the research at two clinics, Vilana-Teknon and Sagrada Familia, in Barcelona, Spain.

In the meantime, he told Reuters Health, roughly 20% of fibromyalgia patients are GH-deficient, and for them GH injections are indicated.

For 18 months, in what may be the largest randomized controlled trial of GH for this indication, researchers studied 120 patients with severe fibromyalgia, as rated by questionnaire, who were receiving standard treatment with amitriptyline, opioids and selective serotonin reuptake inhibitors.

The trial had two arms. In one group, patients took GH continuously for 12 months. In the other, patients took a placebo for the first six months, then GH for the next six months. At month 12, both groups stopped the GH treatments. Follow-up continued until month 18.

At the 93rd annual meeting of the Endocrine Society in Boston on June 5, Dr. Cuatrecasas reported that at 12 months, the number of tender points had fallen to less than 11 out of a possible 18 (i.e., below the threshold for a fibromyalgia diagnosis) in 53% of patients in the 12-month group and in 33% of those who took a placebo for six months (p<0.05).

Patients treated for the full year also had better scores on quality of life surveys and the Fibromyalgia Impact Questionnaire. On the questionnaire's visual analogue scale, 57% of the patients who took GH for 12 months improved more than 30%, compared to 37% of the control group. And 39% of the treatment group improved more than 50%, compared to 22% of the controls.

At month 13, the first month of the medication withdrawal phase, and through the end of the study, all scores in both groups declined significantly.

Doctors often ignore endocrine defects such as thyroid disorders, obesity and deficiencies in vitamin D, cortisol and GH in their fibromyalgia patients, according to Dr. Cuatrecasas

They should screen for these problems, he said. "In the particular field of GH deficiency," he suggests, "doctors should at least look for IGF1, a simple lab marker that is valuable for screening."

Merck, which manufactures GH injections, funded the study.

Rob Goodier • Reuters Health Information © 2011