EVALUATION OF AUTOIMMUNITY IN BENIGN EUTHYROID GOITER

Abstract

The thyroid is a brownish-red and highly vascular gland placed anteriorly in the lower neck, extending from the level of the fifth cervical vertebra down to the first thoracic. The gland varies from an H to a U shape and is formed by 2 elongated lateral lobes with superior and inferior poles connected by a median isthmus overlying the second to fourth tracheal rings. Occasionally, the isthmus is absent and the gland exists as 2 distinct lobes. Each lobe is 50-60 mm long . Thyroid weight varies but averages iS-30 g in adults (slightly heavier in womeni 1>.

Under the middle layer of deep cervical fascia, the thyroid has an inner true capsule, which is thin and adheres closely to the gland with continuations as septae into the gland, dividing it into lobes and lobules. The lobules are composed of follicles, the structural units of the gland, consisting of a layer of simple epithelium enclosing a colloid.-filled cavity.Epithelial cells are of 2 types: principal cells (ie, follicular) and parafollicular cells (ie, C, clear, light cells). Principal cells are responsible for formation of the colloid (iodothyroglobulin), whereas parafollicular

cells produce the hormone calcitonin. ( 2

The arterial supply to the thyroid

gland comes from the superior and inferior thyroid arteries and, 4 · occasionally, the thyroidea ima. These arteries have abundant collateral anastomoses with each other, both ipsilaterally and contralaterally. The