Over 20 million Americans are being treated for thyroid disease and an estimated 2 million more, predominantly women, are estimated to have undiagnosed thyroid problems. The hormones made by the thyroid gland, thyroxine or T4 and triiodothyronine or T3, work all over the body to regulate metabolism. The extent of their presence throughout the body means that disruptions to the function of the thyroid can lead to symptoms in almost any system.
Low Energy
One of the most common symptoms affecting people with thyroid problems is a low energy level. When the thyroid is functioning below its optimal capacity it affects the central nervous system, causing fatigue, weakness and sleep disturbances. The fatigue that accompanies thyroid problems may not improve after a good night's sleep. Increasing the level or activity of thyroid hormone can shorten the amount of time spent sleeping and increase the energy level throughout the day.
Less commonly, the thyroid may be overactive, causing an increase in production or activity of thyroid hormones. Accompanying symptoms may include agitation, sleep disturbances and weakness as muscles are metabolized more quickly. Although metabolism and energy level are increased, the endurance often does not match the increased energy level and fatigue may come easily with activity.
Weight Changes
Because of its close relationship to metabolic rates and the action of thyroid hormones on fat cells, thyroid problems often lead to difficulty maintaining weight. An overactive thyroid can lead to weight loss without a significant change in appetite. More commonly, a thyroid that is underfunctioning will slow down weight loss even with exercise and diet changes. The health consequences of these extra pounds can be serious.
A study done at the University of Pittsburgh and reported in the February 2009 edition of the journal "Medicine and Science in Sports and Exercise" found that people with subclinical hypothyroidism who changed their diet and exercised saw less improvement in physical fitness, muscle metabolism and insulin resistance than people with healthy thyroid function. Insulin resistance can lead to diabetes and heart disease, the leading cause of death in the United States. If exercise and healthy diet changes are not leading to improvements in health, checking thyroid function might reveal important obstacles.
Cardiovascular Disease
Hypothyroidism has been extensively studied for its relationship to cardiovascular disease. Levels of lipoprotein(a), a subtype of LDL, better known as "bad cholesterol," appear to be elevated even in subclinical hypothyroidism, where the thyroid function is low but within normal limits. The autonomic nervous system, the branch of the nervous system that regulates processes such as pulse and respiration, appear to be affected as well. This can be experienced as shortness of breath on exertion or heart palpitations. While more studies are needed to define these relationships between the thyroid and cardiovascular system, researchers at the Mayo Clinic's Division of Endocrinology found in 2009 that research to date indicates that treatment of subacute hypothyroidism can improve these serious risk factors for heart disease.
Mood and Cognition Changes
Depression, anxiety and changes in cognition may be caused by problems with thyroid function. The sleepiness that accompanies hypothyroidism, heart palpitations and agitation from hyperthyroidism and sleep disturbances from either state can make simple depression, anxiety or cognition changes much worse. Simple management of the thyroid can make a tremendous difference in the body's ability to manage emotional stress of all kinds.
Mood changes can occur even when thyroid levels do not warrant a diagnosis of thyroid disease. A review of of the literature performed in July 1998 by David Cooper, M.D., and outlined in an editorial for the "Annals of Internal Medicine" highlighted the importance of screening for and treating subclinical hyper- and hypothyroidism. This article suggested that treatment for subclinical hypothyroidism could reduce the chances a person may show signs of depression, bipolar disorder or cognitive dysfunction.
Menstrual Cycle Changes
Thyroxine, the main hormone produced by the thyroid gland, is needed to make estrogen, an important hormone in regulating menstrual cycles. When estrogen levels change, cycles may become heavier or more painful. Levels of lutenizing hormone (LH) and follicle stimulating hormone (FSH) change in response to the estrogen level. These hormones released from the pituitary gland in the brain help choreograph the hormone fluctuations that maintain healthy menstrual cycles and reproduction. This can mean ovulation is less regular or the chances of miscarriage are elevated. The libido may be affected by thyroid problems as well.
Other Common Symptoms
Changes in the smooth muscle function of the intestines may lead to constipation in hypothyroidism or diarrhea with hyperthyroidism.
Dry skin, or thickening of skin over the lower leg or hands, can occur as part of the connective tissue called glycosaminoglycans break down less efficiently.
Bone density may be affected by the increase in metabolic rate that accompanies hyperthyroidism, raising the risk of osteopenia or osteoporosis.
References
- Subclinical Thyroid Disease: A Clinician's Perspective. David Cooper, MD. "Annals of Internal Medicine"
- Subclinical Hypothyroidism: An Update for Primary Care Physicians. Fatourechi V. Mayo Clinic Proc.
- Successful Treatment with Levothyroxine for Idiopathic Hypersomnia Patients with Subclinical Hypothyroidism. Shinno H, et al. "General Hospital Psychiatry"
- Improvements in Insulin Sensitivity are Blunted by Subclinical Hypothyroidism. Amati F, et al. "Medicine and Science in Sports and Exercise"
