Thyroid Gland – A bowtie or butterfly-shaped gland located in the lower part of the neck, in front of and around the windpipe, that secretes hormones that control the body’s metabolism.

Underactive Thyroid – too little thyroid hormone. Symptoms include weight gain, constipation, dry skin, and sensitivity to the cold. Also called hypothyroidism.

Hypothyroidism – Insufficient production of thyroid hormones.

Larynx – voice box, located in the throat above the thyroid gland.

Hashimoto thyroiditis – A progressive disease of the thyroid gland characterized by the presence of antibodies directed against the thyroid, and by infiltration of the thyroid gland by lymphocytes.

Thyroid Nodules – Simply put, thyroid nodules are lumps that commonly arise within an otherwise normal thyroid gland. Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland, so they can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can even sometimes be seen as a lump in the front of the neck.

Triiodothyronine – A hormone made by the thyroid gland. It has three iodine molecules attached to its molecular structure. It is the most powerful thyroid hormone, and affects almost every process in the body, including body temperature, growth, and heart rate.

Thyroxine – Abbreviated T4. A hormone made by the thyroid gland that has four iodine molecules attached to its molecular structure. T4 and other thyroid hormones help regulate growth and control the rate of chemical reactions (metabolism) in the body.

Trachea – also known as the windpipe, located below the thyroid gland

Pituitary glad – A small oval endocrine gland attached to the base of the vertebrate brain and consisting of an anterior and a posterior lobe, the secretions of which control the other endocrine glands and influence growth, metabolism, and maturation. Also calledhypophysis, pituitary body.

Thyroid stimulating hormone – A hormone secreted by the pituitary gland that controls the release of T4 by the thyroid gland. Also known as TSH.

Neurohypophysis – The posterior portion of the pituitary gland, having a rich supply of nerve fibers and releasing oxytocin and vasopressin. Also called posterior lobe of hypophysis.

antithyroid agents – Drugs; methamazole (Tapazole) or Propylthiouracil (PTU), drugs used to make it more difficult for iodine to get into your thyroid gland.

MTC - medullary thyroid cancer

Graves disease – Generalized diffuse overactivity (“toxicity”) of the entire thyroid glandwhich becomes enlarged into a goiter. Graves disease is the most common cause of hyperthyroidism.

Thyroidectomy – The surgical removal of all or part of the thyroid gland.

Goitrogen – A substance or product that may cause thyroid enlargement and formation of a goiter, such as soy or millet

Thyroglobulin – A protein in the thyroid gland that can be used as a marker for thyroid disease and thyroid cancer.