A large endocrine gland situated in the base of the neck (see illustration). It consists of two lobes, one on either side of the trachea, that are joined by an isthmus (sometimes a third lobe extends upwards from the isthmus). The thyroid gland consists of a large number of closed follicles inside which is a jelly-like colloid, which contains thyroglobulin and the principal active substances that are secreted by the gland. The thyroid gland is concerned with regulation of the metabolic rate by the secretion of thyroid hormone, which is stimulated by thyroid-stimulating hormone from the pituitary gland and requires trace amounts of iodine. The C cells of the thyroid gland secrete calcitonin.
Position of the thyroid gland.
Subjects: Medicine and Health — Science and Mathematics.