Morphological and Immunohistochemical Changes in Thyroid Gland Due to Exposure of Formalin in Albino Rats

Abstract

Background: Formaldehyde is the most widely used chemical in daily life; thus, chronic exposure to formaldehyde has been revealed to have negative effects on different organs in humans and animals. Objective: This research was designed to investigate variable thyroid changes arising from chronic formaldehyde exposure by measuring different histomorphometry parameters in accordance with estrogen receptor and S-100 protein expression. Materials & Methods: In this experiment, two hundred (200) rats were used and divided into two groups (100 male and 100 female), each group was subdivided into control and experimental groups each with 50 rats. The rats were exposed to formaldehyde using (20 ml =92.6ppm formaldehyde), 5hrs / d, for 21 days. Animals were sacrificed, and thyroid sections were examined for histomorphometry using H&E stain and immunohistochemistry for localization of estrogen receptor and S-100 protein Results: Significant decrease obtained in histomorphometrical measurements in the area of the colloids, area of follicles and width, height and number of the follicles in the cells of both experimental groups with no significant effect of gender in both control and experimental groups except in the height of the cells which showed significant decrease in female more than male. Formaldehyde exposure showed no significant effect on localization of estrogen receptor but significant increase of S-100 protein localization in both male and female groups. Conclusion: Formaldehyde had similar effect on histological structure of thyroid gland in both sexes causing disruption of thyroid follicles. Exposure of Formaldehyde had no effect on estrogen receptor but caused an increase in S-100 protein localization in both sexes. Key words: Formaldehyde, Rat, Estrogen receptor, S-100 protein