Thyroid gland

Thyroid gland, ductless two-lobed endocrine gland lying in front of the trachea in the neck. The principal hormones secreted by the thyroid play a crucial role in regulating the rate at which cells oxidize fuels to release energy and thus strongly influence growth. Thyroid stimulating hormones (TSH) are released by the pituitary gland. Undersecretion (hypothyroidism) in adults leads to myxedema, with mental dullness and cool, dry, puffy skin. Oversecretion (thyrotoxicosis) produces nervousness, weight loss, and increased heart rate. Goiter, an enlargement of the gland, may result when the diet is deficient in iodine.

See also: Gland; Hormone.