What the Thyroid Is and How It Works
The thyroid is a butterfly-shaped gland you can feel at the base of your neck, just below your larynx (voice box). It's one of your body's most important glands. Two lobes (the "wings" of the butterfly) fit on either side of your windpipe. The thyroid gland manufactures and stores thyroid hormone (TH), often referred to as the body's metabolic hormone. Among other jobs, TH stimulates enzymes that combine oxygen and glucose, a process that increases your basal metabolic rate (BMR) and body heat production. The hormone also helps maintain blood pressure, regulates tissue growth and development and is critical for skeletal and nervous system development. It plays an important role in the development of the reproductive system.
The thyroid gland can malfunction in one of three ways:
1. It can release too little TH, a condition known as hypothyroidism (underactive thyroid), where your body's metabolic rate slows down. Symptoms vary widely and include fatigue, menstrual cycle irregularities, depression, low body temperature, weight gain, dry or itchy skin, constipation and thin, dry hair or hair loss. Hypothyroidism can occur spontaneously, develop during or after pregnancy or after treatment for hyperthyroidism. You can be born with this condition.
2. It can release too much TH, a condition known as hyperthyroidism (overactive thyroid), causing your body's metabolic rate to speed up. Symptoms of hyperthyroidism include nervousness/irritability, weight loss, fast or irregular heart rate, heat intolerance or increased perspiration, changes in appetite and sleep disturbances (such as insomnia), muscle weakness, shorter and lighter menstrual flow and more frequent bowel movements.
3. The thyroid gland's tissue can overgrow, resulting in a nodule or small lump in part of the gland. Thyroid nodules are the most common thyroid disorder, occurring in up to 50 percent of people over age 50. Most nodules are harmless growths. The ATA estimates that less than one in10 thyroid nodules is cancerous. While most nodules have no symptoms, are never detected and are harmless, some can be large enough to press against the windpipe and cause difficulty swallowing or a cough. A nodule can also become overactive, suppressing the rest of the gland and causing hyperthyroidism.
If you think you may have a thyroid disorder or are concerned about any of the symptoms listed above, it's important to talk to your health care provider.
To learn more, visit our Thyroid Disorders section.