Greater fatigue was linked to unusual levels of two thyroid hormones in women with functional somatic syndromes (FSS), a term used to describe symptoms that are difficult to explain and which includes fibromyalgia among its conditions.
Specifically, women with FSS had higher levels of the thyroid hormone thyroxine (fT4) and lower levels of thyroid-stimulating hormone (TSH). Low TSH levels were also associated with adverse and traumatic events in early life.
The study, “Thyroid functioning and fatigue in women with functional somatic syndromes – role of early life adversity” were published in the journal Frontiers in Physiology.
FSS is the term given to a set of distinct physical symptoms that are not attributed to any specific disease, including chronic pain and fatigue, irritable bowel syndrome, and fibromyalgia.
Fatigue, either physical or mental, is commonly associated with several diseases, but about one-third of the patients experiencing it find it difficult to explain to their doctors.
Fatigue is also one of the most frequent symptoms of thyroid diseases. Researchers were not surprised by this association, since the hypothalamic-pituitary-thyroid (HPT) axis — a set of glands that produce hormones and other substances — is involved in regulating energy levels.
Alterations in the HPT axis have been observed in healthy women who report troubling events in early life, like childhood traumas.
Early life adversity is also prevalent in women with FSS and, for that reason, researchers decided to investigate if the function of HPT axis is related to fatigue and early life in a group of patients.
Sixty-three women were recruited, including 33 with FSS. They were analyzed for hormone levels (TSH, fT4 and triiodothyronine or fT3); general, physical and mental fatigue, using the multidimensional fatigue inventory (MFI); and early life adversity using the childhood trauma questionnaire (CTQ).
Fibromyalgia, along with chronic fatigue, was found in 14 FSS women (42 percent), and seven patients (21 percent) had both fibromyalgia and irritable bowel syndrome. Six had all three syndromes.
No differences were observed in healthy women and those with FSS regarding thyroid hormone levels.
However, patients with lower TSH levels and higher fT4 levels had general and physical fatigue — with increases in fatigue matching more extreme changes in those two levels .
Data collected also showed that lower levels of TSH correlated with early life adversity, including emotional neglect, physical neglect, physical abuse, and sexual abuse.
The researchers concluded that the HPT axis was linked to fatigue sensation, as well as to early life adversity in women with FSS.
“The present study provides an initial evidence of a link between TSH and fT4 concentrations and fatigue as experienced by patients with FSS. Moreover, TSH levels were directly linked with early life adversity in patients,” they wrote.
“We believe that larger, prospective studies in concert with experimental studies testing the integrity of the HPT axis in a standardized manner are most likely to advance the field at this stage,” the team added.