The thyroid gland at the base of the neck plays an important role in day-to-day activities. The hormone it produces—simply called thyroid hormone, which comes in two varieties called triiodothyronine (or T3) and thyroxine (or T4)—directs and regulates the metabolic process that powers almost every cell in the body. It is necessary that the thyroid produces the right amount of hormone; either too much or too little will cause disease, lead to fatigue, ad raise miscarriage risk.
Excess thyroid hormone—hyperthyroidism—overclocks the body’s metabolism. When the thyroid is pumping out too much T3 and T4, for example due to a congenital condition called Graves’ disease, doesn’t always have any symptoms at all. The effects can include irritability, muscle weakness, diarrhea, weight loss, and hair loss. An extreme and acute instance of hyperthyroidism is called a thyroid storm, which causes fever, vomiting, irregular heartbeat, and diarrhea and requires emergency treatment.
A goiter, or growth on the neck, is often a symptom of too little hormone, though it can also result from too much. Primarily, people who are suffering from under-active thyroid—hypothyroidism—have some of the opposite symptoms, such as weight gain and constipation. The poor metabolism caused by insufficient production of the hormone can result in muscle soreness, sluggishness, depression, and forgetfulness. Hypothyroidism often results from not enough of the mineral iodine in the diet, though in many places salt has iodine added to avoid this. Seafood is also a good source of iodine.
Thyroid hormone levels can be measured in the blood. This test is generally performed on people experiencing symptoms of hyperthyroidism—particularly thyroid storm—and hypothyroidism. In addition, thyroid hormone tests are recommended for people with high cholesterol, who often have under-active thyroid as well. Some experts recommend even healthy people get checked every five years after turning 35. Thyroid disease affects nearly 30 million Americans, many of whom show no symptoms. The wrong level in either direction can often be treated if it is caught, but first it must be caught.