Fibromyalgia and the Thyroid
The thyroid is a gland in the neck. Thyroid-stimulating hormone triggers the thyroid to use iodine from the diet to produce hormones called thyroxin (T4 – contains four molecules of iodine) and triiodothyronine (T3 – contains three molecules of iodine), which control metabolism throughout the body, and are also important in growth, especially in the unborn baby. The thyroid also produces calcitonin, a hormone that controls the levels of calcium in the blood.
HypothyroidismIf the thyroid does not produce enough of the thyroid hormones, this causes a disorder called hypothyroidism. Symptoms can include tiredness, feeling the cold, depression, muscle and joint pain, neck swelling, dry and brittle hair and nails, dry, coarse and itchy skin, hair loss, weight gain, slow heart beat, menstrual irregularities, infertility, recurrent miscarriage, low blood pressure, high cholesterol, ‘brain fog’ and constipation. Doctors treat patients with hypothyroidism with a replacement dose of thyroxin.
MisdiagnosisHypothyroidism has many similar symptoms to both chronic fatigue syndrome and fibromyalgia syndrome, and all three are most common in women aged between 20 and 50. This can lead to confusion between the disorders, and potential cases of misdiagnosis.
Fibromyalgia Syndrome and the ThyroidIn a study of patients with fibromyalgia syndrome, published in 2007, all the people tested had normal thyroid hormone levels, but 41% of them showed one or more thyroid antibodies in their blood. Thyroid antibodies are a sign of autoimmune disease, where the body is using its own immune system to attack its own organs, and may suggest that the thyroid is beginning to fail. The patients showing signs of autoimmune thyroiditis also were more likely to report dry eyes, burning or pain with urination, allodynia (where a stimulus that is usually pain-free triggers pain), blurred vision, and sore throat, and were more likely to be post-menopausal.
In another study, 34% of patients with fibromyalgia syndrome had thyroid antibodies, compared with 19% of those without the disorder. The fibromyalgia syndrome patients with the antibodies tended to be older than the fibromyalgia syndrome patients who did not have the antibodies, and were more likely to be postmenopausal, complain of a dry mouth, and have had a psychiatric disorder.
These two studies may suggest that fibromyalgia syndrome patients with thyroid antibodies have worse symptoms than fibromyalgia syndrome patients without the antibodies.
Patients with chronic fatigue syndrome sometimes also have thyroid antibodies in their blood. While other studies have also suggested a link between autoimmune thyroiditis and fibromyalgia syndrome, this does not yet confirm that the thyroiditis is causing the fibromyalgia syndrome. Research is ongoing.