The thyroid is a butterfly-shaped gland located at the base of your neck, just below your Adam’s apple. The “wings” or lobes of this gland wrap around your windpipe.

The thyroid gland is part of the endocrine system, which is composed of the glands in the body that produce hormones. Hormones are chemicals made in one part of the body that travel by the bloodstream to have effects at other parts of the body.

Your thyroid gland is responsible for releasing thyroid hormone into your bloodstream where it is carried to every cell and organ in your body. Thyroid hormone helps regulate the rate at which your body works (metabolism). If you have too much thyroid hormone, your metabolic rate speeds up, a condition called thyrotoxicosis. If you have too little thyroid hormone, your metabolic rate slows down, a condition called hypothyroidism.

The thyroid gland works together along with the pituitary gland and the hypothalamus in the brain to regulate your metabolism. The pituitary gland, for example, constantly monitors the amount of thyroid hormone in your blood. If it senses that your thyroid gland is not producing enough of this hormone, it “instructs” your thyroid gland to produce more by releasing thyroid stimulating hormone or “TSH” into your bloodstream.

Your doctor can determine if your thyroid gland is producing the right amount of thyroid hormone by testing the level of TSH in your blood. With few exceptions, your thyroid gland is underactive hypothyroidism if your TSH level is high, and your thyroid gland is overactive hyperthyroidism if your TSH level is low.