The thyroid gland produces the hormones thyroxine, triiodothyronine, and calcitonin. Thyroxine and triiodothyronine are produced by thyroid folliclar cells. Thyroid cells absorb iodine from certain foods and combine the iodine with tyrosine, an amino acid, to make thyroxine (T4) and triiodothyronine (T3).