Your thyroid is a gland in the front of your neck that makes two hormones: thyroxine (T4) and triiodothyronine (T3). These hormones guide a variety of crucial functions in your body such as your metabolism, your blood pressure, your digestion, your heart rate, and your ability to maintain a comfortable body temperature. Your hypothalamus, a part of your brain, and your pituitary gland, a small gland right below the hypothalamus, typically tell your thyroid how much of each hormone to produce.