The term hypothyroidism refers to an under active thyroid gland that does not produce sufficient quantities of various hormones. The thyroid gland is located at the base of the front of the neck, just below the Adam’s apple. It produces hormones that have a significant impact on the body’s metabolism and overall health, including thyroxine (T-4), triiodothyronine (T-3), and calcitonin. T-4 and T-3 regulate metabolism and heart rate, control body temperature, and regulate the production of proteins in the body, while calcitonin regulates the level of calcium in the blood. When the thyroid gland fails to produce adequate amounts of these hormones, hypothyroidism can result. This can occur as a result of any number of underlying conditions and circumstances, including certain autoimmune diseases, treatment for hyperthyroidism (overactive thyroid gland), radiation therapy, surgery, and some medications. Pregnancy and dietary iodine deficiency can also result in hypothyroidism.
Anyone can develop hypothyroidism, however middle-aged women are the most likely to develop the condition. Other risk factors include the presence of an autoimmune disease, a family history of autoimmune disease, those who have been treated with radioactive iodine or who have received anti-thyroid medications, individuals who have received radiation therapy to their neck or upper chest, and individuals who have had surgery to remove a portion of their thyroid gland.
Symptoms of hypothyroidism appear gradually over time, and they vary according to the severity of the underlying hormone deficiency. Initial symptoms are often characteristic of a decreased metabolism, and include fatigue and an overall sense of sluggishness. Additional symptoms include increased sensitivity to cold, constipation, pale and dry skin, facial puffiness, a hoarse voice, high cholesterol, unexplained weight gain, muscular aches and pains, joint stiffness and pain, muscle weakness, heavy menstrual periods, brittle nails and hair, and depression. In addition, as the body continuously stimulates the thyroid gland in an effort to produce more thyroid hormone, the thyroid gland itself may enlarge, resulting in what is known as a goiter.
Any of these symptoms can worsen if hypothyroidism is left untreated. Depressive symptoms can become more severe and cognition may become impaired. Hypothyroidism can cause an enlarged heart and lead to heart failure. In addition, long-standing untreated hypothyroidism can result in damage to the nerves and result in nerve pain, numbness and tingling, and loss of muscle strength and control. Women of reproductive age may experience impaired ovulation due to hypothyroidism, and babies born to women who have hypothyroidism are at an increased risk for birth defects, as well as intellectual and developmental problems. In rare instances, hypothyroidism can become severe and result in a condition known as myxedema. Symptoms of this condition include low blood pressure, decreased breathing rate and body temperature, and possible coma. Myxedema can occasionally be fatal.
Hypothyroidism is diagnosed on the basis of symptoms as well as the results of blood tests that measure blood levels of as thyroid stimulating hormone (TSH) and, occasionally, T-4. TSH is produced by the pituitary gland and tells the thyroid gland when to produce T-3, T-4, and calcitonin. Blood tests that reveal a low level of T-4 and a high level of TSH indicate the presence of hypothyroidism. This is because the body produces excess TSH in an effort to stimulate the thyroid gland when it is not functioning properly.
Treatment for hypothyroidism generally involves taking a synthetic thyroid hormone medication daily, which then reverses the deficiency and results in improved symptoms in as few as one to two weeks. However, treatment must be continued over one’s lifetime in order to maintain sufficient thyroid hormone levels. In order to determine the most appropriate dose, blood levels of TSH will likely be checked after two or three months. Side effects of overactive hormone production due to treatment include increased appetite, insomnia, irregular heartbeat, and shakiness. The drug most commonly used to treat hypothyroidism – levothyroxine – causes practically no side effects, however certain medications and dietary supplements, as well as foods, may impair the body’s ability to absorb the medication properly. These include soy products, high-fiber diets, iron supplements, cholestyramine (a cholesterol-lowering medication), aluminum hydroxide (a common ingredient in many antacids), and calcium supplements.
Apart from conventional drug therapies, limited information is available regarding the use of alternative therapies to treat hypothyroidism. It is well known that supplemental iodine can protect against the development of hypothyroidism in individuals whose diets are deficient in natural sources of iodine. For this reason, iodine is added to salt in the United States and many other countries in an effort to curb the incidence of hypothyroidism. Synthetic tiratricol, which is a naturally-occurring derivative of T-4, has been shown to be likely effective at treating fetal hypothyroidism during pregnancy (Nicolini et al., 1996; Asteria et al., 1999). In addition, some research suggests that selenium supplements may be useful in the treatment of hypothyroidism among elderly patients, however findings are conflicting and studies are limited in number (Olivieri et al., 1995; Rayman et al., 2008).
Hypothyroidism and Fibromyalgia Research
Both hypothyroidism and fibromyalgia share a considerable number of symptoms, including fatigue, muscular aches and pain, joint pain and stiffness, cold sensitivity, depression, and cognitive dysfunction. Therefore, hypothyroidism must be considered in the differential diagnosis of a patient who presents with those symptoms (Brecher & Cymet, 2001). Unlike fibromyalgia, however, specific laboratory tests are available to determine the presence of hypothyroidism. Furthermore, treatment with levothyroxine can confirm a diagnosis when laboratory findings are of borderline significance (i.e., if symptoms improve following treatment, the patient likely has hypothyroidism).
Apart from their symptomatic overlap, research has looked at other relationships between hypothyroidism and fibromyalgia. Several studies have investigated the incidence of various rheumatic diseases, including fibromyalgia, among patients with thyroid dysfunction. Some studies have determined an increased incidence of fibromyalgia among individuals with autoimmune thyroid disease (Soy et al., 2007; Suk et al., 2012; Pamuk & Cakir, 2007), whereas others have found no increased incidence of fibromyalgia among individuals with hypothyroidism (Carette & Lefrancois, 1988). In addition, other studies have evaluated the possible role that resistance to thyroid hormone may play in the development of fibromyalgia. For example, a recent study by Bazzichi et al. evaluated whether patients with disrupted thyroid functioning, including those with hypothyroidism, were predisposed to developing fibromyalgia. While no correlation was found between hypothyroidism and fibromyalgia in the 13 fibromyalgia patients evaluated, the authors did find that 12 patients with Hashimoto’s thyroiditis (an inflammatory, autoimmune disease of the thyroid gland that often results in hypothyroidism) developed comorbid fibromyalgia. Based on their findings, the authors concluded that there may be a causal role for thyroid autoimmunity in the development of fibromyalgia (Bazzichi et al., 2012). These findings have been supported by similar results from other studies (Suk et al., 2012), as well as evaluated from a theoretical perspective (Garrison & Breeding, 2003). Conversely, Kotter et al. (2007) have suggested that for some patients, fibromyalgia may be an early sign of an emerging autoimmune disease (Kotter et al., 2007).