The thyroid gland is responsible for regulating how your body uses energy through metabolism. If your thyroid gland becomes overactive, due to illness, too much iodine in the diet, infection or tumor, that regulatory ability becomes impaired. This can lead to a variety of symptoms such as fatigue and weight loss. Left untreated, hyperthyroidism can also lead to toxicity of thyroid hormone in your body, known as thyrotoxicosis, which can lead to life-threatening complications, which usually involve the cardiovascular system. Hyperthyroidism also appears to have an effect on levels of several neurotransmitters, including dopamine. Treatment for hyperthyroidism is intended to restore the balance of thyroid hormone and, in turn, affected biochemicals.
Dopamine
Dopamine is a neurotransmitter that is responsible for the regulation of movement, emotional response and feelings of pleasure and pain. If dopamine levels decline, these functions subsequently decline, as seen in Parkinson's Disease, which is a depletion of dopamine. Some medications and recreational drugs such as cocaine, have a significant effect on dopamine levels, either by increasing the amount of dopamine released or by preventing its reuptake by neurotransmitters. As a result, you experience feelings of pleasure, heightened senses and additional energy. Over time, however, your body becomes desensitized to the extra dopamine, known as tolerance, which then requires additional amounts of the drug to elicit the same feeling. This is the mechanism behind drug addiction.
Thyroid Hormone and Dopamine
Thyroid hormone appears to have an association with dopamine levels in the brain. A 1984 article published in the "European Archives of Psychiatry and Neurological Science" found a strong correlation between elevated levels of dopamine and low levels of thyroid hormone in people with schizophrenia. Conversely, a study published in 1987 in the "European Journal of Endocrinology" found that low levels of dopamine were associated with elevated thyroid hormone levels in patients with Graves' Disease. Graves' disease is a condition characterized by hyperthyroidism and comorbid symptoms.
Treatment of Hyperthyroidism
Treatment of hyperthyroidism involves one of three options: surgical removal of the thyroid gland, radioactive iodine destruction of the gland or antithyroid medications. The American Thyroid Association explains that the choice of treatment depends on factors such as severity of the disease and symptoms, age of the patient and extenuating circumstances such as pregnancy. Any therapeutic approach to hyperthyroidism has the goal of achieving a balance of thyroid hormone. If the thyroid gland is rendered inoperative, supplemental thyroid medication is provided to restore balance. Given the effects of hyperthyroidism on dopamine activity, research suggests that restoring balance should subsequently restore balance of associated neurotransmitters, including dopamine.
Other Considerations
Hyperthyroidism causes disruption of neurotransmitters in the brain and body and has been found to be associated with symptoms of this disruption. A study published in the Nov.-Dec. issue of "Archives of Medical Research" found a significant association between hyperthyroidism and reported depression and anxiety. These findings suggest, according to the researchers, that health care professionals should focus treatment for hyperthyroidism not only on the effects of excess thyroid hormone, but also their effects on other neurochemicals. Adjunct therapies, such as the administration of antidepressant medications, may be indicated for some individuals with hyperthyroidism.
References
- National Institutes of Health: Hyperthyroidism
- "Journal of Neural Transmission"; Dopamine Receptor Site Sensitivity in Hyperthyroid Guinea Pigs: A Possible Model of Hyperthyroid Chorea; H. L. Klawans, et al.; 1973
- University of Texas: Dopamine - A Sample Neurotransmitter
- "European Archives of Psychiatry and Neurological Sciences"; Altered Interrelationship of Dopamine, Prolactin, Thyrotropin and Thyroid Hormone in Schizophrenic Patients; Marie Luise Rao, et al.; 1984
- "European Journal of Endocrinology"; Increased Luteinizing Hormone Sensitivity To Dopaminergic Inhibition in Graves' Disease; J. Tourniaire, et al.; 1987
- American Thyroid Association; Treatment Guidelines for Patients With Hyperthyroidism and Hypothyroidism; Peter A. Singer, MD, et al.; 1995
