Low levels are associated with impaired thinking, lack of energy, muscle weakness, and intolerance to cold. In a 2003 study, however, there was no association
between IGF levels and fibromyalgia
. Researchers in the study noted that lower levels of IGF also occur with aging and obesity, which must be factored in when studying its role in fibromyalgia. Nevertheless, severe growth hormone deficiency, which may be treatable, has been observed in a subset of fibromyalgia patients.