Hemiagenesis of the Right Lobe and Isthmus of the Thyroid Presenting as Multinodular Goitre

The thyroid gland is the first endocrine gland to start developing in the embryo. Morphological and structural developmental anomalies of the thyroid gland are relatively rare. Thyroid developmental anomalies (TDA) (excluding biochemical abnormalities) can be divided into three groups namely agenesis (or athyreosis), dysgenesis, and anomalies due to persistence of the thyroglossal tract (Jain and Pathak, 2010). Thyroid dysgenesis includes thyroid hemiagenesis, thyroid hypoplasia, ectopic, aberrant and accessory thyroid tissue. Hemiagenesis of the thyroid gland (THA) occurs when one half of the thyroid gland fails to develop. It is considered to be the rarest developmental abnormality of the thyroid gland (McHenry et al, 1995). The exact incidence is unknown as often the patients may be clinically asymptomatic. The estimated prevalence is about 0.05 to 0.2% (Maiorana et al, 2003 and Shabana et al, 2000). Thyroid hemiagenesis anomaly was first described in 1852 by Handfield-Jones (Handfield Jones, 1852). Only about 310 cases have been reported in world literature to date (Tiwari et al, 2008).