Due to the likelihood of physical and mental health impacts following the unprecedented accident at the Fukushima Dai-ichi Nuclear Power Plant, the Fukushima prefectural government decided to conduct the Fukushima Health Management Survey to assist in the long-term health management of residents. This included thyroid ultrasound examination for all children in Fukushima. For appropriate evaluation of ultrasound screening of the thyroid, it is important to understand its reference data of thyroid findings in children in general. In order to analyze the frequencies of specific thyroid findings, we conducted ultrasound screening of the thyroid by the same procedures as used in Fukushima in 4,365 children, aged 3 to 18 years, from three Japanese prefectures. Overall, thyroid cysts were identified in 56.88% and thyroid nodules in 1.65% of the participants. Thyroid cysts and nodules with a maximum diameter of more than 5 mm were identified in 4.58% and 1.01%, respectively, and age-adjusted prevalences were 3.82% and 0.99%, respectively. Although the prevalence of cysts and nodules varied among the examination areas, no significant differences were observed among the three examination areas in the prevalence of cysts and nodules with a maximum diameter of more than 5 mm. Also, the prevalence of thyroid cysts and nodules, especially those with a maximum diameter of more than 5 mm, significantly increased with age, and showed a female predominance. We also identified ectopic thymus (1.95%), diffuse goiter (1.40%), ultimobranchial body (0.73%), lymph node swelling (0.21%) and thyroid agenesis (0.05%). This is the first ultrasound description of the age-adjusted prevalence of thyroid cysts and nodules, or of the prevalence of abnormalities other than cysts and nodules, such as ectopic thymus, in relation to age, in the general Japanese child population. We contend that this can provide relevant information for the Fukushima Health Management Survey and future population studies.

During the Chernobyl Nuclear Power Plant (CNPP) accident on 26 April 1986, large amounts of radionuclides were released and spread to vast areas. Inh

Hypertension frequently occurs in subclinical hypothyroidism (SCH). By bolstering thyroid inflammation, anti-peroxidase antibody (TPO-Ab) causes autoimmune thyroiditis, which is one of the most common causes of SCH. Since the absence of thyroid cysts is associated with TPO-Ab (+) based on the indication of latent thyroid damage, we explored the potential mechanism underlying the association among TPO-Ab, SCH, hypertension, and thyroid cysts. A cross-sectional study of 1,483 Japanese aged 40–74 years was conducted. Thyroid cysts were defined as those having a maximum diameter of ≥ 2.0 mm, containing no solid component. TPO-Ab (+) was positively associated with SCH with hypertension (adjusted odds ratio [OR] and 95% confidence interval [CI], 2.62 [1.40, 4.89]) but not with SCH without hypertension (0.84 [0.37, 1.89]), respectively. Moreover, among participants without thyroid cysts, SCH was positively associated with hypertension (2.15 [1.23, 3.76]) but not among participants with thyroid cysts (0.58 [0.16, 2.16]), respectively. TPO-Ab was positively associated with SCH with hypertension, but not with SCH without hypertension. In addition, status of thyroid cysts might act as a determinant factor on the association between SCH and hypertension. These findings are efficient tools to clarify the background mechanism that underlies SCH.

Our recent studies indicate that thyroid cysts have clinical implications. Thyroid cysts could have a positive effect on the supply of thyroid hormones. Both hyperthyroidism and hypothyroidism cause hypertension. Hypothyroidism, but not hyperthyroidism, is a risk factor for atherosclerosis. Therefore, thyroid cysts could be associated with hypertension, and atherosclerosis might influence the association between thyroid cysts and hypertension. To evaluate the clinical significance of thyroid cysts, a cross-sectional study was conducted with 1801 Japanese aged 40–74 years. Thyroid cysts were significantly positively associated with hypertension in participants without atherosclerosis. However, there was a significant inverse association in those with atherosclerosis. The potential confounding factor adjusted odd ratios and 95% confidence intervals (95% CIs) were 1.49 (95% CI 1.17–1.90) for participants without atherosclerosis and 0.49 (95% CI 0.24–0.98) for those with atherosclerosis. The present study demonstrates that thyroid cysts have clinical implications because thyroid cysts support thyroid hormone activity. Our findings provide sufficient evidence to develop a risk assessment for hypertension for the general population, even though further research is required.

Background: Anti-thyroid peroxidase antibody (TPO-Ab) has been shown to cause autoimmune thyroiditis by inducing a deleterious influence on thyroid hormone synthesis. Further, thyroglobulin, which has an important role in thyroid hormone synthesis, is reported to be high in the fluid from thyroid cysts. Therefore, TPO-Ab could be associated with the presence of thyroid cyst, partly by affecting the activity of thyroid hormone synthesis. Methods: To investigate the association between TPO-Ab and thyroid cysts, we conducted a cross-sectional study of 1432 Japanese with normal thyroid function [i.e., normal range of free triiodothyronine (free T3) and free thyroxine (free T4)] between the ages of 40 and 74 years, who participated in an annual health check-up. Results: In men, the statistical power did not reach a statistical significance value. Additionally, subjects with TPO-Ab showed lower odds ratios (ORs) of thyroid cysts than those without TPO-Ab. In women, subjects with TPO-Ab showed significantly lower ORs of thyroid cysts than those without TPO-Ab. The fully adjusted ORs were 0.68 (0.40, 1.18) for men and 0.40 (0.27, 0.60) for women. When evaluating the association between logarithmic values of TPO-Ab titer and thyroid cysts in both men and women, a notable inverse correlation was observed. The fully adjusted ORs were 0.68 (0.50, 0.92) for men and 0.68 (0.57, 0.81) for women. Conclusion: TPO-Ab titer revealed to be inversely associated with thyroid cysts among Japanese with normal thyroid function. The presence of a thyroid cyst could indicate a lower risk of having TPO-Ab among the general population with normal thyroid function.