Does TSH Trigger the Anti-thyroid Autoimmune Processes? Observation on a Large Cohort of Naive Patients with Thyroid Hemiagenesis

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.

Thyroid Hemiagenesis in a Thyroiditis Prone Mouse Strain

“…In addition, it is unlikely that the TSHR A-subunit transgene contributed to thyroid hemiagenesis in 1 mouse because (a) it occurred in 2 wild-type NOD.H2 h4 mice and (b) the transgene is located on chromosome 1 [17] and not on chromosomes 2, 12, 5, and 16, the locations of Pax 8, TTF1, Shh, and Tbx1. It should be emphasized that the genetic basis for thyroid hemiagenesis in humans could be identified in only a minority of cases with no common or specific gene identified [3,38], although thyroid autoimmunity was frequently present [39].…”

Hemiagenesis of the thyroid gland detected by coincidence—what is the clinical relevance?

“…Interestingly, Szczepanek-Parulska et al. [ 43 ] reported in their study group a higher prevalence of thyroid antibodies in patients with THA compared with individuals with normal thyroid glands, thus suggesting evidence that THA may also promote the development of immune thyroid disorders.…”

“…Because patients with THA seem to be prone to hypothyroidism, regular control of thyroid hormones, in particular TSH, seems to be warranted to detect any thyroid dysfunction at an early stage. Due to the higher reported rate of autoimmune disorders in THA [43], a consequent evaluation of thyroid antibodies seems to be warranted when THA has been diagnosed.…”

Thyroid Hemiagenesis: Narrative Review and Clinical Implications

“…Szczepanek-Parulska et al in 2016, performed a large cohort study of sixty-five patients with THA and revealed a high prevalence of elevated thyroid auto-antibodies with patients having more clinical manifestation of thyroid autoimmune pathology [ 38 ]. This could be attributed to a hypothesis in which excessive stimulation of TSH receptors may lead to the “leak” of some thyroid autoantigens such as thyroglobulin or thyroid peroxidase into the circulation leading to an autoimmune response and resultant autoantibody thyroid development [ 39 ].…”