The thyroid gland is located in the neck below the thyroid cartilage, or Adam’s apple. It is extremely important because every cell in the body depends on the hormones the thyroid produces to determine how quickly to convert calories and oxygen into energy. This process is known as metabolism. (Hormones are chemical substances that help control certain cells and organs.) Hormones from the thyroid gland affect various bodily processes, including growth and development, regulation of calcium levels, and heart and digestive functions.

The thyroid makes and stores three important hormones:

  • Thyroxine (T3): The major hormone from the thyroid, it is essential for metabolism, as well as normal growth and development.
  • Triiodothyronine (T4): A vitally important hormone, it affects heart rate, body temperature, growth, development, and metabolism. The thyroid normally produces about four times more T4 than T3, but T3 is a much more powerful hormone.
  • Calcitonin: It helps form bones and regulates calcium levels in the body.

The thyroid makes these hormones by using iodine and tyrosine. Iodine, a trace mineral, is found in many foods but is highest in kelp, eggs, strawberries, and dairy foods. It is even added to table salt. Tyrosine, an amino acid, is also found in these and many soy-based foods.

Once the thyroid converts iodine and tyrosine into hormones, they are released into the bloodstream at the command of the pituitary gland, a peanut-sized gland in the brain. It does this by releasing a thyroid stimulating hormone, or TSH.

A healthy thyroid functions without much notice. However, people with thyroid problems can experience several symptoms, including:

  • Swelling in the neck
  • Heat or cold intolerance
  • Unexplained weight loss (or gain)
  • Constipation or diarrhea
  • Menstrual irregularity
  • Muscle or joint pains

Symptoms depend on how the thyroid is malfunctioning.

Hyperthyroidism is a condition where the thyroid overproduces hormones. This can result in symptoms associated with increased metabolism, including fast heart rate, nervousness, insomnia, frequent bowel movements, fatigue, weight loss, and others.

Hypothyroidism occurs when the thyroid doesn’t produce enough hormones. This often slows metabolism, which results in weight gain, depression, fatigue, decreased libido, hair loss, and intolerance to cold temperatures, among other symptoms.

These two are the most common thyroid conditions. Other conditions affecting the thyroid include:

  • Thyroid cancer
  • Thyroid nodules: noncancerous growths on the thyroid
  • Hashimoto’s disease: inflammation of the thyroid
  • Goiter: enlargement of the thyroid