EJMS

Abstract

Background: Amiodarone is a very effective drug, widely used for arrhythmia, but it is associated with many side effects involving many different organs. Aim of the work: This work was conducted to elucidate the effect of amiodarone on the thyroid gland and the possible protective role of vitamin E. Material and Methods: The present study was carried out on fifty adult male albino rats. Their average weight was 200 grams. They were divided into four groups as following: The first group (group I, control group): this group consisted of twenty rats and was further subdivided into two equal subgroups: Plain control: consisted of ten rats. They were kept without any treatment (five rats were sacrificed after three weeks and five rats were sacrificed after six weeks) and served as control for all the experimental groups. Sham control: consisted of ten rats. Each rat received sunflower oil (the solvent used to dissolve vitamin E) ingested by gavage for three weeks. The second group (group II, amiodarone treated group): Consisted of ten rats. Each rat received an oral dose of amiodarone for three weeks by gavage. The third group (group III recovery group): consisted of ten rats. Each rat received an oral dose of amiodarone for three weeks by gavage then the drug was stopped for three weeks to evaluate recovery. The fourth group (group IV, amiodarone + vitamin E treated group): this group consisted of ten rats. Each rat received an oral dose of amiodarone followed by vitamin E by gavage for three weeks. By the end of each assigned period, the rats were anaesthetized by ether vapour. The thyroid gland of the sacrificed animals were dissected out, the specimens were taken and prepared for Histological and Electron microscopic studies. Results: The present study revealed that Amiodarone administration in second group resulted in loss of normal follicular architecture. Many follicles appeared shrunken. Many follicles were empty or contained scanty pale colloid. Some follicles appeared lined by more than one layer of cells. Others showed interruption of their basement membrane. Thickened collagen fibers inbetween the thyroid follicles were observed. The apical border of the follicular cells showed few irregular detached microvilli. The nuclei of the follicular cells were almost irregular and showed chromatin condensation. The cytoplasm of most follicular cells revealed numerous dilated rough endoplasmic reticulums. Numerous lysosomes were frequently seen. After three weeks of stopping Amiodarone in third group, the follicles were nearly regular in outlines. Some follicles were filled with homogenous eosinophilic colloid. However, few scattered follicles exhibited shrunken pale colloid, very few follicles were empty. Some few follicles showed exfoliated cells in their lumina. Some few follicles were still lined by more than one layer of follicular cells. In comparison to fourth group, less collagen fibers were observed in-between thyroid follicles. Ultrathin sections of this group showed some follicular cells with rounded euchromatic nucleus, moderate number of lysosomes and moderately dilated rough endoplasmic reticulum. While, other follicular cells exhibited irregular nucleus, dilated rough endoplasmic reticulum and many cytoplasmic vacuoles. In the fourth group, administration of vitamin E with amiodarone for three weeks resulted in obvious structural improvement where most of the follicles were lined by a single layer of cuboidal cells. The lumina were filled with homogenous eosinophilic colloid with very few vacuolations. The majority of follicular cells had rounded nuclei with occasional detection of ballooned cells and dark nuclei. Mild collagen fibers were detected among thyroid follicles comparable to group II. Most follicular cells exhibited rounded euchromatic nuclei. Moderate number of short microvilli were projecting into the colloid. Moderate numbers of lysosomes were also noted. Conclusion: The present work showed that amiodarone administration leads to many histological changes in the thyroid gland. Some of these changes show reversible effect in the recovery period. On the other hand, vitamin E administration with amiodarone has great effect to prevent many of these changes.