Clinical meaning
The thyroid gland is a butterfly-shaped endocrine organ located anterior to the trachea between C5-T1 vertebral levels, consisting of two lateral lobes connected by an isthmus overlying tracheal rings 2-4. Each lobe is approximately 4 cm in length, 2 cm in width, and 2-4 cm in depth, with a normal gland weight of 15-25 grams. The gland is invested by the pretracheal fascia and attached to the trachea by the ligament of Berry, which is why it moves superiorly with swallowing — a key differentiating feature from other anterior neck masses. A pyramidal lobe (remnant of the thyroglossal duct) is present in approximately 40-50% of individuals, extending superiorly from the isthmus. The recurrent laryngeal nerve runs in the tracheoesophageal groove immediately posterior to the thyroid lobes and is at risk during thyroidectomy — injury produces hoarseness. The superior and inferior parathyroid glands lie on the posterior surface of each thyroid lobe and are at risk of inadvertent removal during surgery, causing hypocalcemia. Blood supply from superior thyroid artery (branch of external carotid) and inferior thyroid artery (branch of thyrocervical trunk) creates a highly vascular gland; a thyroid bruit indicates increased vascularity seen in Graves disease. Advanced thyroid examination includes assessing gland size (normal, enlarged/goiter), consistency (soft, firm, hard/stony), symmetry, tenderness, mobility, and presence of nodules.