In a Past study, it was found that 1 out of 3 fibromyalgia patients has low levels of growth hormone and other related hormones. The finding encourages a series of clinical studies on growth hormone therapy as a potential treatment for some fibromyalgia patients.
What is Growth Hormone?
The natural human growth hormone (GH) is the hormone that regulates cell growth, cell development and cell repair. GH is essential for physical growth, strength development and renew of cells. It also play a role in other body chemistry such as metabolism. GH level reduces as one age which explains why a person stop growing physically and have less energy as one matures.
GH deficiency can be found in some children with genetic disorders. The lack of GH not only affects their physical development, but also can lead to symptoms akin to fibromyalgia such as muscle pain and weakness, fatigue and sensitivity to low temperatures.
How does Growth hormone work?
The production of GH, which is regulated by another hormone known as the growth hormone releasing hormone (GHRH), happens in the pituitary gland in the brain. The GHRH tells the pituitary gland to secrete GH into the bloodstream. In order to activate cell repair work, GH has to be released from the brain, enter and travel through the bloodstream to the liver where it is required to stimulate the production of insulin-like growth factor (IGF-1) hormone responsible for cell repair work.
Fibromyalgia and growth hormone, what is the link?
Studies have shown that 30% of fibromyalgia patients is found with GH deficiency. This subset of fibromyalgia patients is observed to have subnormal levels of serum IGF-1 in their blood which suggest that they are also lacking in GH. GH deficiency is known to produce fibromyalgia-like symptoms such as muscle pain, weakness and fatigue in children. A 1999 study suggest that the lack of GH and IGF-1 can contribute to fibromyalgia pain. It is believed that the deficiencies can hinder with cell repair and renewal in affected fibromyalgia patients and hence result in more severe chronic pain. Studies investigating the effect of GH treatment in fibromyalgia patients showed positive effects including reduction of pain, reduction of tender points and improvement in quality of life in fibromyalgia subjects
Growth Hormone treatment for fibromyalgia
The reason behind the low levels of GH seems to be due to a hypothalamic-pituitary-GH axis dysfunction leading to impaired GH secretion. Though the exact cause of impaired GH secretion is uncertain, clinical studies have narrowed down to two possibilities: presence of increased levels of somatostatin tone which reduces GHRH activity and GH resistance or insensitivity of GH receptors.
Currently, there are two types of treatments targeting growth hormone in fibromyalgia patients.
Human growth hormone therapy
The discovery of subnormal levels of IGF-1 in some fibromyalgia patients in a 1997 study, published in the Journal of Rheumatology, sparked a series of research on the efficacy of human growth hormone therapy in fibromyalgia patients. In two separate studies done in 1998 and 2007, growth hormone treatment has been found to benefit a specific group of low IGF-1 fibromyalgia patients, with or without the concurrent use of other medications respectively. The benefits include reduction in tender points, relief in morning stiffness and improvement in muscle weakness.
These findings encouraged the development of human growth hormone (hGH) therapy for fibromyalgia where hGH is injected directly into patients. However, the treatment lacks universality as a treatment option for all fibromyalgia patients as it is only available to suitable patients and incurs a high cost ranging from USD500-1000 a month. There are also concerns with prolonged usage of hGH.
Pyridostigmine therapy to suppress Somatostatin
Some studies also suggest that the impaired secretion of GH could be due to high levels of hypothalamic somatostatin tone inhibiting the activation of GHRH which in turn result in low secretion of GH. A 2002 study published in the Journal of Arthritis Rheumatology found that fibromyalgia patients have a subnormal GH response to exercise and that low GH response can be reversed with the use of Pyridostigmine drug, a somatostatin-blocking agent, which reduced somatostatin tone.
In view of the cost and concerns of long term administration of hGH, 2 clinical trials published in 2007 and 2008, investigated the effect of Pyridostigmine (also known by brand name Mestinon) in combination with exercise therapy to increase GH levels in fibromyalgia patients. In the 2008 trial, subjects reported significant improvement in sleep and anxiety after 6 months of treatment though no significant impact were seen in other fibromyalgia symptoms. Nevertheless, researchers remain positive in the direction of the study to finding a long term Pyridostigmine therapy by adjusting its dosage and duration of exercise and perhaps introducing GH-releasing hormone secretagogues.
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- Jones KD, Deodhar AA, Burckhardt CS, Perrin NA, Hanson GC, Bennett RM. A combination of 6 months of treatment with pyridostigmine and triweekly exercise fails to improve insulin-like growth factor-I levels in fibromyalgia, despite improvement in the acute growth hormone response to exercise. J Rheumatol. 2007 May;34(5):1103-11.
- K. D. Jones, PhD, C. S. Burckhardt, PhD, A. A. Deodhar, MD, N. A. Perrin, PhD, G. C. Hanson, MS, and R. M. Bennett, MD. A Six-Month Randomized Controlled Trial of Exercise and Pyridostigmine in the Treatment of Fibromyalgia. Arthritis Rheum. 2008 Feb; 58(2): 612–622.