A ductless gland, consisting of irregularly spheroidal follicles, lying in front and to the sides of the upper part of the trachea, and of horseshoe shape, with two lateral lobes connected by a narrow central portion, the isthmus; occasionally an elongated offshoot, the pyramidal lobe, passes upward from the isthmus in front of the trachea. It is supplied by branches from the external carotid and subclavian arteries, and its nerves are derived from the middle cervical and cervicothoracic ganglia of the sympathetic system. It secretes thyroid hormone and calcitonin.
1) A gland located beneath the voice box (larynx) that produces thyroid hormone. The thyroid helps regulate growth and metabolism. Underactive thyroid is also called hypothyroidism. This is a condition in which the thyroid gland doesn't make enough thyroid hormone. Lack of thyroid hormone will slow down your metabolism and cause weight gain.
2) The endocrine gland normally situated in the lower part of the front of the neck; secretes, stores and releases the iodine dependent thyroid hormones thyroxine and triiodothyroine which play major endocrine roles in regulating metabolic rate; also secretes thyrocalcitonin.