The thyroid gland, situated against the front of the trachea, produces thyroxin, a hormone that influences all cells by regulating the oxygen they use. Thus, thyroxin regulates metabolism because oxygen is needed to release energy from nutrients at a cellular level. Hypothyroidism occurs when too little thyroxin is released by the thyroid gland. Too much thyroxin is known as hyperthyroidism. Each condition produces different generalized physical signs and symptoms. The most common type of hyperthyroidism is Grave's disease. The most common cause of hypothyroidism is autoimmune thyroiditis, or Hashimoto's disease.
Goiter
The thyroid gland can become visibly swollen due to lack of dietary iodine, inflammation, hypothyroidism, hyperthyroidism, the formation of benign solid or fluid-filled nodules in the gland or, rarely, cancer. A large goiter may produce tightness in the throat, cough, and difficulty breathing or swallowing. The MayoClinic.com states that most goiters are painless and that small goiters may not cause problems or require treatment.
Changes in Energy Level
Too much thyroxin speeds up the heartbeat, causing nervousness and anxiety. Other symptoms of hyperthyroidism include tremors, feeling warm, sweating excessively and difficulty sleeping. Too little thyroxin causes chronic fatigue and a slow pulse. Feeling cold and constipation are other symptoms of hypothyroidism. The University of Maryland Medical Center reports that over time, clinical depression, snoring, and sleep apnea may develop due to below normal functioning of the thyroid gland.
Changes in Weight
The basal metabolic rate is a measurement of how much oxygen the body uses at rest. Too much thyroxin produces a higher BMR than too little of the hormone, which produces a low BMR. People with a high BMR burn more calories faster and on average experience symptoms of weight loss. Those with a low BMR burn fewer calories, making it easier for them to gain weight and retain fluids. According to the American Thyroid Association, weight gain due to hypothyroidism is generally limited to 5 to 10 lbs. Inactivity may also be a factor in weight gain.
Changes in Physical Features
Besides weight loss or gain, other signs of thyroid disease may be noticeable. In hypothyroidism, the skin becomes dry and may have a yellow complexion; the hair becomes brittle and breaks easily. Symptoms of hyperthyroidism may include a surprised look because the eyes protrude, having been pushed forward by swollen connective tissues. Called ophthalmopathy, it happens gradually and is not painful. Discomfort may occur due to eye dryness, irritation, redness, puffiness around the eyes and sensitivity to light. A study of subjects with Grave's disease by researchers at the University of Amsterdam found that smoking increases the risk of developing eye problems, worsens symptoms and interferes with the efficacy of treatment. The findings were published in the October 2002 issue of "Thyroid." Blurred vision due to weakness of the eye muscles is a symptom in half of Grave's disease cases, according to an article published in the August 2005 issue of "American Family Physician."
References
- Mayo Clinic: Goiter
- University of Maryland Medical Center: Hypothyroidism Symptoms
- American Thyroid Association: Thyroid and Weight Brochure
- "Thyroid"; Epidemiology and Prevention of Graves' Ophthalmopathy; W.M. Wiersinga, L. Bartalena; October 2002
- "American Family Physician"; Hyperthyroidism Diagnosis and Treatment; J. Reid, S. Wheeler; Aug. 15, 2005
