Structural and stereological analysis of rat thyroid gland after exposure to an electromagnetic field

Abstract

Considering that the thyroid gland is one of the most sensitive organs to ionizing radiation, we decided to investigate the effects of a low frequency electromagnetic field (LF-EMF) as non-ionizing radiation on the thyroid structure of male rats exposed for five months to a 50 Hz magnetic field of decreasing intensity 500 μT to 50 μT along their cages. Stereological analysis showed a significant reduction in: volume density of the follicles (p<0.05), volume density (p<0.01) and thickness (p<0.01) of the follicular epithelium, as well as the thyroid activation index (p<0.01) while the volume density of the colloid (p<0.01) and interfollicular tissue (p<0.05) were significantly increased compared to the control. The most prominent cytological changes in the thyroidal follicular cells were the absence of apical protrusions, the rare presence of intracellular colloid droplets and the extremely low follicular epithelium in some areas of the glands. These morphometrical and morphological alterations indicate that long-term exposure to LF-EMF induced disturbance of normal thyroidal structure.