Evaluation of rat thyroid gland morphophysiological status after three months exposure to 50 Hz electromagnetic field.

Objective of our study was to use morphophysiological criteria in order to determine the sensitivity of male rat thyroid gland to an extremely low frequency electromagnetic field (ELF-EMF) influence and the ability of the gland to repair after period of exposure. Animals were exposed to 50Hz, 50-500 microT ELF-EMF for 3 months when a part of them (group I) were sacrificed, while the rest of animals were subjected to recovery evaluation of the gland and sacrificed after 1 (group II), 2 (group III) and 3 (group IV) weeks. Histological and stereological analyses were performed on paraffin and semifine thyroid gland sections. Serum T3 and T4 were also determined. Histological and stereological analyses showed that the volume density of follicular epithelium and thyroid activation index decreased, while the volume density of colloid and capillary network increased in group I, II and III. The values of all these parameters in group IV were similar to corresponding controls. Serum T3 and T4 concentrations were significantly lower in all exposed animals, except in group I. Results of this study demonstrate that after significant morphophysiological changes caused by ELF-EMF exposure thyroid gland recovered morphologically, but not physiologically, during the investigated repair period.