Abstract
Thyroid hemiagenesis (THA) is a rare abnormality characterized by the absence of one thyroid lobe. Elevated thyroid stimulating hormone (TSH) level and higher incidence of thyroid diseases were reported in THA. The aim of the study is to evaluate the thyroid autoimmunity incidence in patients with THA and influence of higher than average TSH level on thyroid volume (TV) and its change with age. The study included a group of naive patients with THA and a control group of subjects with bilobate thyroid. All patients underwent clinical examination, thyroid ultrasound, scintiscan and laboratory tests. In the studied and control group the presence of thyroid autoantibodies (TAb) was evaluated. The THA group consisted of 65 patients. In THA group 53.85 % of patients were positive for TAb. Patients with positive TAb were older (46.0 ± 18.3 years) than those with negative (35.0 ± 19.8 years); p = 0.02. The incidence of TAb was lower in controls (13.85 %, p < 0.0001). In the study group, positive correlation between the age and TV (r = 0.46, p = 0.0001), and negative correlations between the age and TSH level (r = −0.31, p = 0.01), and TSH concentration and TV (r = −0.35, p = 0.004) were found. In a subgroup of 30 patients with THA negative for TAb, even stronger correlations were observed. The median single lobe volume and median TSH level were higher in patients with THA when compared to controls (13.60 vs 8.20 ml, p < 0.0001; 3.23 vs 1.48 µU/ml, p < 0.0001, respectively). Patients with THA constitute an in vivo model of long-term thyroid TSH overstimulation. Further studies are needed to reveal, whether TSH overstimulation may be the trigger for thyroid autoimmunity.
Highlights
Thyroid hemiagenesis (THA) is a form of thyroid dysgenesis that is characterized by the absence of one thyroid lobe, with or without isthmus
The aim of the present study is to examine on a largest ever evaluated group of patients diagnosed with THA prevalence/incidence and profile of thyroid autoimmunity and possible effect of high thyroid stimulating hormone (TSH) level on thyroid volume (TV) and its change with the patient age
Most available literature about this disorder consists of case reports describing the coexistence of THA and other pathologies
Summary
Thyroid hemiagenesis (THA) is a form of thyroid dysgenesis that is characterized by the absence of one thyroid lobe, with or without isthmus. To date, reported prevalence of this disorder varies 0.05–0.5 % of the population; the true incidence is still unknown (Duarte et al 2009; Gursoy et al 2008; KorpalSzczyrska et al 2008; Maiorana et al 2003; Shabana et al 2000). Since the remaining lobe is usually capable to cover hormonal requirements and sustain clinical euthyroidism, THA is most often discovered accidentally while performing different neck examinations. Cases of overt hypothyroidism due to lack of one thyroid lobe were reported in children by Calaciura et al (2002) and Devos et al (1999). The study published previously by our team remains the first systematic analysis of a large cohort of 40 patients with THA (Ruchala et al 2010). It was demonstrated that mean thyroid stimulating hormone (TSH) and free triiodothyronine (FT3) values were
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