The function of the thyroid gland is to regulate the body's metabolism. The thyroid gland is prone to several very distinct problems, some of which are extremely common. These problems can be broken down into (a) those concerning the production of hormone (too much, or too little), (b) those due to increased growth of the thyroid causing compression of important neck structures or simply appearing as a mass in the neck, (c) the formation of nodules or lumps within the thyroid which are worrisome for the presence of thyroid cancer, and (d) those which are cancerous. Disorders of the thyroid gland include overactivity, underactivity, tumorous growths and inflammatory lesions. Causes may be dietary or hereditary. Thyroid problems often go undetected because the symptoms are fairly non-specific, e.g. fatigue, inability to concentrate and modest weight gain.
The thyroid gland is the biggest gland in the neck. It is situated in the anterior (front) neck below the skin and muscle layers. The thyroid gland takes the shape of a butterfly with the two wings being represented by the left and right thyroid lobes which wrap around the trachea. The sole function of the thyroid is to make thyroid hormone. This hormone has an effect on nearly all tissues of the body where it increases cellular activity.
A human thyroid produces T4, T3, T2, T1 and calcitonin. For nearly 100 years, hypothyroid patients were given desiccated porcine thyroid (dried thyroid gland from pigs), and doses were increased until all symptoms were gone. Synthroid became the treatment of choice for hypothyroidism by the 1970s. This drug contains only the storage thyroid hormone known as T4.
The TSH (thyroid stimulating hormone) test was created in 1973. It is used to diagnose thyroid problems. It measures the hormone TSH produced by the pituitary gland. A feedback loop exists where the pituitary gland produces more or less TSH in response to the level of thyroid hormones in the bloodstream, and the thyroid produces more or less hormone based on the level of TSH. The normal range for the TSH test has been lowered several times (the American Association of Clinical Endocrinologists now recommends a normal TSH range from 0.3 to 3.0); patients are usually not diagnosed with hypothyroidism until the TSH is above 3.3. In the case of autoimmune thyroid problems, the TSH can be within the normal range, yet antibodies are attacking the thyroid. As many as 1 in 5 Americans may suffer from undiagnosed hypothyroidism.
Thyroid disorders are a known problem among more than 20 million people in the United States. Yet as many as 13 million others may have undiagnosed thyroid dysfunction, clearly affecting their quality of life.
A random survey of thyroid dysfunction in 25,862 apparently healthy and active people found that 9.5 percent of those studied had hypothyroidism, or underactive thyroid, and 2.2 percent had hyperthyroidism, or overactive thyroid.
As mandatory iodine supplementation of salt has proceeded, “The spectrum of thyroid diseases has undergone a significant change ranging from simple goiter to toxic nodular goiter, Hashimoto’s thyroiditis, and thyroid cancer accompanied by the increase in iodine intake, especially for thyroid cancer with an annual increase of 14.51% in China...high iodine intake is likely to lead to occurrence of thyroid diseases, such as Hashimoto’s thyroiditis, nodular goiter, and hyperthyroidism, through a long-term mechanism” (Zhao, H. et al. (2014). Correlation between iodine intake and thyroid disorders: a cross-sectional study from the South of China. Biological Trace Elements Research, 162(1-3), 87-94).