Hyperthyroidism among Galvanization Workers Due to Exposure to Zinc Fumes

Sahar A. Farahat1, Laila A. Rashed2, Aisha M. Samir1, and Dalia M. Abdel Hamid1

1 Department of Industrial Medicine and Occupational Diseases, Cairo, Egypt
2 Department of Biochemistry Faculty of Medicine, Cairo University, Cairo, Egypt

Corresponding author: Sahar Ali Farahat
    Faculty of Medicine,
    Kasr El-Ini, Department of Industrial Medicine and Occupational Diseases
    Cairo, Egypt
    Mobile: 002 / 0104875015
    E-mail: Farahat_sahar@yahoo.com

CEJOEM 2007, Vol.13. No.3-4.: 240-250

Key words:
Galvanization, zinc, zinc fumes, hyperthyroidism, thyroid hormones

Abbreviations:
FT4
FT3
TSH		 = free thyroxin
= free triiodothyronine
= thyroid stimulating hormone

Abstract:
The intimate relation between zinc as a trace element and the thyroid function has been extensively investigated in many studies.
    Aim: This study aimed at clarifying the effect of excessive occupational exposure to zinc dust and fumes among galvanization workers on thyroid functions.
    Methods: The study population consisted of 22 galvanization male workers and an equal group of matched males. Every participant of this study was subjected to occupational history taking, questionnaire on the symptoms of thyrotoxicosis, full clinical examination with special emphasis on thyroid gland examination, assessment of zinc levels in plasma and urine as exposure indices for zinc exposure and measuring thyroid function hormones namely, free thyroxin (FT4), free triiodothyronine (FT3), and thyroid stimulating hormone (TSH).
    Results: Both urine and plasma zinc levels were significantly higher in the exposed group (p<0.05) compared to their referents. However, the zinc plasma level was not correlated with duration of work. Surprisingly, the study revealed marked significant increase in the mean values of FT4 and FT3 (p<0.005) with significant lowering of TSH (p<0.05) among the exposed group. Moreover, FT4 was in significant positive correlation with duration of work and plasma level of zinc.
    Conclusion: This study points to the possibility of the occurrence of thyroid stimulation due to excessive occupational exposure to zinc dust and fumes similarly to many other studies which demonstrated enhancement of thyroid functions after increasing zinc supplementation. However, larger scale studies are recommended to verify this possibility and its mechanism.

Received: 24 December 2007
Accepted: 30 April 2008
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