Patogênese das doenças tiroidianas autoimunes

Incidence of TPOAb over a 4-year follow-up period: results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Objective

Although some previous data have suggested a high iodine intake in Brazil, the prevalence of antithyroperoxidase antibodies (TPOAb) in the country is compatible with rates from countries with adequate iodine intake. This observation emphasizes the importance of knowing the incidence of TPOAb in Brazil.

Methods

This prospective analysis included euthyroid participants with negative TPOAb at baseline and a thyroid function assessment at a 4-year follow-up. TPOAb was measured by electrochemiluminescence and considered positive when titers were ≥34 IU/mL. TSH and free T4 (FT4) levels were determined by a third-generation immunoenzymatic assay. The incidence of TPOAb is expressed in percentage per year or as a cumulative incidence within the 4-year follow-up period.

Results

Of 8,922 euthyroid participants (mean age 51.1 years; 50.9% women) with a negative TPOAb test at baseline, 130 presented incident TPOAb at the 4-year follow-up, yielding an annual incidence of TPOAb of 0.38%/year (95% confidence interval [95% CI], 0.37-0.39%/year) and a cumulative incidence over 4 years of 1.46% (95% CI, 1.21-1.71%). In men, the annual incidence was 0.32% (95% CI, 0.31-0.33%), and the cumulative incidence over 4 years was 1.23% (95% CI, 0.90-1.56%). In women, the annual incidence was 0.43%/year (95% CI, 0.42-0.44%/year) and the cumulative incidence over 4 years was 1.67% (95% CI, 1.30-2.04%). The only factor associated with incident TPOAb was the occurrence of thyroid diseases at follow-up. No differences in TPOAb incidence were detected across ELSA-Brasil research centers.

Conclusion

Based on the results of this study, the incidence of TPOAb per year and at a 4-year follow-up period are compatible with those of a country with adequate iodine intake.

Prevalence of antithyroperoxidase antibodies in a multiethnic Brazilian population: The ELSA-Brasil Study

OBJECTIVE

In this study, we aimed to describe the prevalence and distribution of positive antithyroperoxidase antibodies (TPOAb) according to sex, age strata, and presence of thyroid dysfunction using baseline data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).

MATERIALS AND METHODS

Thyroid hormone tests were obtained from each study participant at baseline. Levels of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) were measured using a third-generation immunoenzymatic assay. Antithyroperoxidase antibodies were measured by electrochemiluminescence and were considered to be positive when ≥ 34 IU/mL.

RESULTS

The prevalence of TPOAb among 13,503 study participants was 12%. Of participants with positive TPOAb, 69% were women. Almost 60% of the individuals with positive TPOAb were white. The presence of positive TPOAb was associated with the entire spectrum of thyroid diseases among women, but only with overt hyperthyroidism and overt hypothyroidism in men.

CONCLUSION

The distribution of positive TPOAb across sex, race, age, and thyroid function in the ELSA-Brasil study is aligned with the worldwide prevalence of positive TPOAb reported in iodine-sufficient areas. In women, the presence of TPOAb was related to the entire spectrum of thyroid dysfunction, while in men, it was only related to the occurrence of overt thyroid disease.

Overt Primary Hypothyroidism in an Industrial Area in São Paulo, Brazil: The Impact of Public Disclosure

Background: Primary hypothyroidism (PH) is the most common thyroid pathology. Purpose: to evaluate the impact of public disclosure of an unexpected number of PH cases on the frequency of patients seeking medical evaluation for endocrinological diseases. Methods: data on 6306 subjects (3356 living in the surroundings of a petrochemical complex and 2950 in a control region) were collected over a 15-year time span. Thyroid function was determined by serum levels of triiodothyronine, thyroxine, free thyroxine and thyrotrophin. Antithyroglobulin and antithyroperoxidase antibodies and sonographic scans of the thyroid were performed in all patients. The data were analyzed via log-linear models to compute odds and odds ratios. Results: An increasing trend in the odds of PH was detected along the observation period with greater slope in the study region than in the control region. The odds of PH in the post-disclosure period (2002 to 2004) are greater than the corresponding ones in the pre-disclosure period (1989 to 2001). Conclusions: This study shows that living in the surroundings of a petrochemical complex may be an important risk factor for PH for both adults and children. Furthermore, public disclosure of such risk factor contributes to the awareness of the problem and to the possibility of an early diagnosis.

[Correlation between iodine urinary levels and pathological changes in thyroid glands]

OBJECTIVES

To determine iodine nutrition in the population and to correlate levels of iodine found in random samples of urine with pathological changes observed in thyroids collected in this population.

MATERIALS AND METHODS

Urinary iodine was determined in 30 random samples of urine and the pathological study was carried out in 55 thyroid glands from corpses received by the Department of Forensic Medicine of Vitória, Espírito Santo, Brazil from May to August 2011.

RESULTS

In 29 urine samples (96.7%) urinary iodine was above the maximum limit recommended by the World Health Organization (WHO), of 300 mg/L. Fourteen thyroids (25.5%) showed the presence of histological changes compatible with thyroiditis. Higher levels of iodine in urine were observed in females and in of thyroid that showed inflammation (thyroiditis).

CONCLUSIONS

We conclude that, in this population, there is excess iodine intake, and greater incidence of inflammatory thyroid disease.

[Graves disease and IgA deficiency as manifestations of 22q11.2 deletion syndrome]

The 22q11.2 deletion syndrome (22q11.2DS) is related to a high phenotypic variability including the velocardiofacial/DiGeorge spectrum. Autoimmune, endocrine and immunodeficiency manifestations have been reportedly associated with the syndrome. The objective of this study was to report a case of 22q11.2DS associated with IgA deficiency and Graves disease and review literature in order to verify the frequency of syndrome alterations. Autoimmune disorders have been increasingly related to 22q11.2DS, and new phenotypes are being incorporated in the clinical spectrum of this syndrome. In our study we found that Graves disease in association with 22q11.2DS was reported in only sixteen patients, and fifteen cases were described in the last 13 years. Based on the incidence and on the amplitude of this recognized spectrum, we reinforce the findings of literature that Graves disease should be included on the 22q11.2DS manifestations, which would lead us to seek it with 22q11.2 deletion patients.

Environmental factors and thyroid autoimmunity

Thyroid autoimmune disease, a multifactorial organ-specific autoimmune disorder, is marking a constant increase worldwide. It is thought to be caused by multiple environmental factors triggering autoimmune response in genetically susceptible individuals, though the exact mechanisms linking environmental factors to thyroid autoimmunity are not as yet well understood. Nevertheless, there is increasing evidence that mainly nutritive factors and environmental pollution by metals and chemicals (e.g. organochlorines, pesticides) are the main factors in the present-day spread of this disease. This review presents an overview of the current knowledge regarding environmental factors, their association with genetics and their impact on the immune system.

Parity is not related to autoimmune thyroid disease in a population-based study of Japanese-Brazilians

BACKGROUND

It has been suggested that the female preponderance for autoimmune thyroid disease might be associated with hormonal differences, abortion, and fetal microchimerism. Findings emerging from the few epidemiological studies on this matter, however, are controversial. In this study, we investigated the hypothesis whether parity, abortion, and the use of estrogens are associated with a higher risk for thyroid autoimmunity.

METHODS

This cross-sectional population-based study examined 675 women from a Japanese-Brazilian population aged above 30 years. Thyroid peroxidase antibodies (TPOAbs), thyroglobulin antibodies (TgAbs), thyrotropin, and free T₄ were measured by immunofluorimetric assays. Urinary iodine concentration was measured using a colorimetric method. Data were analyzed in logistical regression models to obtain the odds ratio (OR) and 95% confidence intervals.

RESULTS

TPOAbs and TgAbs were present in 11.6% and 13.6% of women, respectively. After adjustment for age, smoking, and urinary iodine concentration, the OR for positive TPOAb (OR, 1.22 [95% confidence interval, 0.73–2.02]) and for positive TgAb (OR, 1.01 [0.63–1.62]) among women who had one or more parities did not differ from those who had never given birth. In addition, we found no association between the presence of thyroid antibodies and previous abortions or the use of estrogens.

CONCLUSIONS

Parity, abortion, and the use of estrogens are not associated with thyroid autoimmunity in this population. These findings reinforce previous reports that advocated against a key role of fetal microchimerism in the pathogenesis of autoimmune thyroid disease.