Evaluation of the effects of chronic occupational exposure to metallic mercury on the thyroid parenchyma and hormonal function
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2020
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International Archives of Occupational and Environmental Health
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Introduction Experiments in animals exposed to mercury (Hg) in different chemical states have shown thyroid parenchymal
and hormone alterations. However, these experiments did not allow the establishment of dose–response curves or provide
an understanding of whether these Hg effects on the thyroid parenchyma occur in humans.
Objective To evaluate the association between chronic occupational exposure to metallic Hg and alterations in thyroid
hormones and gland parenchyma 14 years after the last exposure.
Methods A cross-sectional study including 55 males exposed in the past to metallic Hg and 55 non-exposed males, paired
by age, was conducted in the Hospital das Clínicas (Brazil) from 2016 to 2017. Serum concentrations of total and free triiodothyronine
(TT3 and FT3), free thyroxine (FT4), thyrotropin (TSH), reverse T3 (RT3), selenium and antithyroid antibody
titers were obtained. The Hg and iodine concentrations were measured in urine. The thyroid parenchyma was evaluated by
B-mode ultrasonography with Doppler. The nodules with aspects suspicious for malignancy were submitted to aspiration
puncture with a thin needle, and the cytology assessment was classified by the Bethesda system. The t test or Mann–Whitney
test, Chi-square test and Spearman correlation were used to compare the exposed and non-exposed groups and examine the
relationships between the variables. Univariate and multivariate logistic regression models were used to trace determinants
of the risk of thyroid hormone alteration. Statistical significance was defined by p < 0.05.
Results The urinary Hg average was significantly higher in the exposed group than in the non-exposed group (p < 0.01). The
mean TSH serum concentration in the exposed group was higher, with a statistically significant difference between the groups
(p = 0.03). Serum concentrations of TSH exceeded the normality limit (4.20 μIU/ml) in 13 exposed individuals (27.3%) and
4 non-exposed individuals (7.3%), with a statistically significant association between the hormonal increase and exposure
to Hg (p = 0.02). In the logistic regression model, exposure to Hg (yes or no) showed an odds ratio = 4.86 associated with
an increase of TSH above the normal limit (p = 0.04). The serum concentrations of RT3 showed a statistically borderline
difference between the groups (p = 0.06). There was no statistically significant difference between the mean TT3, FT3 and
FT4 serum concentrations in the Hg-exposed group compared to the non-exposed group. The proportions of the echogenicity
alterations were higher in the exposed group compared to the non-exposed group (27.3% versus 9.1%; p = 0.03). Papillary
carcinomas were documented in three exposed individuals and one non-exposed individual. A follicular carcinoma was
recorded in one non-exposed individual.
Conclusions Due to the higher serum TSH concentration and the prevalence of parenchymal alterations in the Hg-exposed
group, even after cessation of exposure, it is recommended that the thyroid status of exposed workers be followed for a long
period.
Como referenciar
CORREIA, M.M.; CHAMMAS, M.C.; ZAVARIZ, J.D.; ARATA, A.; MARTINS, L.C.; MARUI, S.; PEREIRA, L.A.A. Evaluation of the effects of chronic occupational exposure to metallic mercury on the thyroid parenchyma and hormonal function. International Archives of Occupational and Environmental Health, v. 93, n. 4, p. 491-502, 2020. DOI: 10.1007/s00420-019-01499-0. Disponível em: http://repositorio.ipen.br/handle/123456789/31075. Acesso em: 26 Apr 2024.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.