Is growth hormone an effective therapy for fibromyalgia?

Growth hormone deficiency in fibromyalgia.

Growth hormone is one of the many chemical mediators of the hypothalamic-pituitary-adrenal axis (HPAA,) a very complex regulatory system affecting nearly every bodily function but especially critical in homeostatic regulation of the stress response.

Is growth hormone low in fibromyalgia?

Some studies (including the second study referenced below) have shown that about one-third of those with fibromyalgia have low growth hormone, and that treatment of this group with growth hormone decreased the number of tender points and improved the Fibromyalgia Impact Questionnaire (FIQ) score.

While a treatment of benefit to one-third of fibromyalgia patients would be welcome, it may be that a substantially larger percent of those with fibromyalgia have some form of growth hormone deficiency. It has been shown that some patients generally have normal growth hormone levels, but that they release less than the expected amount of growth hormone in response to exercise. In fact one study found that only 153 of 165 fibromyalgia patients (93%) had less than expected growth hormone release in response to exhaustive exercise. Perhaps nearly all fibromyalgia patients have some degree of growth hormone deficiency?

That seems a reasonable possibility, since growth hormone deficiency has been linked to diminished energy, depressed mood, impaired thinking, poor memory, reduced exercise capacity, muscle weakness, and cold intolerance – all of which are common in fibromyalgia. In addition, the average growth hormone level was previously shown to be nearly 36% lower in 500 fibromyalgia patients vs 152 controls (see the abstract on PubMed.)

Or maybe not. Like everything else (it seems) regarding fibromyalgia, there are conflicting results. This study found no difference in growth hormone levels between 24 women with fibromyalgia and 27 healthy controls after correcting for age and obesity, both of which are associated with diminished growth hormone production.

Growth hormone therapy among a sub-set of fibromyalgia patients.

What does seem reasonably certain is that growth hormone deficiency is observed in at least some of those with fibromyalgia.

The studies that follow looked at the effect of growth hormone in those with documented growth hormone deficiency.

Note that low growth hormone is indicated by low serum (blood) concentrations of insulin-like growth factor 1 (IGF-1.) IGF-1 is considered a “surrogate marker” for growth hormone. It’s level correlates with average growth hormone secretion over the course of 24 hours. (IGF-1 is produced by the liver in response to growth hormone stimulation – so low growth hormone leads to low IGF-1.)

One recent study (first reference below) investigated the use of growth hormone as an additional therapy among those who had severe symptoms of longstanding duration and who also had low IGF-1.

While the trial involved relatively few patients (a total of 24, only half of which received growth hormone) the results were impressive.

Those receiving growth hormone in addition to their standard therapy had a 60% decrease in the number of tender points and a substantial reduction in FIQ score relative to controls.

Most patients who responded to growth hormone therapy did so within the first several months.

Improvement in FIQ among those treated with growth hormone.

Among those receiving growth hormone therapy, the initial average FIQ was 80.28 (very high, indicating a very severe impact of fibromyalgia symptoms.) That score decreased to an average of 43.57 after 12 months – a total average decrease of 36.71 points, or nearly 46%.

In contrast, the control group had an initial average FIQ score of 79.23, which dropped to 72.02 after 12 months.

The net therapeutic benefit (treatment response minus control response) was 29.5, still a substantial 36.75% decrease.

The minimum FIQ reduction that makes a significant difference is about 14%. So patients receiving human growth hormone clearly had very significant improvement.

Average FIQ Score with and w/o Growth Hormone Therapy

Further investigation of growth hormone therapy is required.

Because growth hormone is chronically low in only some fibromyalgia patients (it seems,) and because growth hormone can reduce only some symptoms (and eliminate none,) it follows that growth hormone deficiency is not the cause of fibromyalgia. It is likely a secondary phenomenon that results from hypothalamic-pituitary-adrenal axis (HPAA) dysfunction.

Growth hormone deficiency in response to exercise appears far more common. Though growth hormone levels at rest among such patients may be normal, they nonetheless had worse symptoms, on average, than those with a normal growth hormone response to exercise.

So it may be that the addition of growth hormone treatment would be of benefit to the vast majority of those with fibromyalgia. But whether the benefit accrues to nearly all, or ‘only’ about a third, the fact that human growth hormone has been shown to substantially relieve symptoms suggests the urgent need for additional investigation.

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