Thyroid gland. Illustration showing the thyroid gland (red), seen surrounding the trachea (windpipe, purple). The blue vessels are veins; the red vessels are arteries. The thyroid gland is located in the neck on the trachea, with the larynx (voicebox) above it. The thyroid is a two- lobed gland, with the two lobes joined by an isthmus of tissue. An important endocrine gland, the thyroid secretes the hormones thyroxine and calcitonin into the blood. These hormones regulate energy levels and body metabolism, including mental and physical development. Lack of thyroid hormones may give rise to cretinism in infants and myxoedema in adults.