Increased risk of thyroid pathology in patients with thyroid hemiagenesis: results of a large cohort case-control study.

Objective: Thyroid hemiagenesis (THA) is an anomaly resulting from the developmental failure of one thyroid lobe. Etiopathogenesis, clinical significance, and management of patients in whom THA is diagnosed are still a matter of debate. The aim of the study is to provide the first systematic analysis of a large cohort of subjects with THA. Design: Forty patients with THA are described in comparison to a control group of 80 subjects with fully developed thyroid gland. Methods: Serum concentrations of thyrotropin (TSH), free thyroxine (FT4), free triiodothyronine (FT3), and thyroid autoantibodies were measured. In 37 patients, thyroid ultrasonography and Tc-99m thyroid scintiscan were performed, followed by fine-needle aspiration biopsy if indicated. The remaining archival three cases were diagnosed with the use of I-131 scintiscan under basal conditions and after TSH stimulation. Results: Patients with THA, while usually clinically euthyroid, presented with significantly higher levels of TSH and FT3 as well as with higher FT3/FT4 concentration in comparison to the control group. Furthermore, a higher incidence of associated functional, morphological, and autoimmune thyroid disorders in patients with THA was observed when compared to subjects with bilobate thyroid (P < 0.05). Conclusions: Our results revealed that individuals with THA are more likely to develop thyroid pathology. The observed high incidence of associated pathologies is presumably due to long-lasting TSH overstimulation. Therefore, THA diagnosis should be followed by systematic observation and adequate levothyroxine treatment in patients with elevated TSH level.