Thyroid gland

(thyroid); an endocrine gland, secreting calcitonin, involved in calcium homeostasis, and the thyroid hormones, such as the iodine- and tyrosine-containing thyroxine (T4) and triiodothyronine (T3), which control development and activity of other bodily functions, the rate of metabolism and the sensitivity to other hormones

Description
The thyroid (gland) consists of irregularly spheroidal follicles, lies in front and to the sides of the upper part of the trachea, below the thyroid cartilage, which is referred to as the Adam's apple in men. The thyroid is 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. The gland 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.

Relevance to Hemoglobinopathies
Thyroid dysfunction is a common occurrence in patients with thalassemia major, with individual reports between 13% and 60%, and observation of primary hypothyroidism in up to 18%. Symptoms of hypothyroidism include chronic fatigue, weakness, weight gain, cold intolerance, muscle cramps, constipation, depression, memory loss, abnormal menses and decreased libido.