الفهرس 
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Abstract
Thyroid hormones are essential for normal growth, development and function of all tissues by regulating basal metabolic rate of all cells, including hepatocytes. Thyrotoxicosis or hyperthyroidism is defined as increased synthesis and secretion of thyroid hormones. One of the main side effects of thyrotoxicosis is the resulting liver damage secondary to the systemic effect of excess thyroid hormones and resulting oxidative stress or due to direct toxic effects of thyroid hormones. Safranal is one of the three major constituents of saffron known by its antioxidant activity. Selenium is a micronutrient which plays a vital role as an antioxidant and anticancer agent. The present study aimed to examine the prophylactic and therapeutic effects of safranal or selenite as a source of selenium against thyrotoxicosis.
Thyrotoxicosis led to significant elevations in serum fT3 and fT4 levels and ALT, AST activities accompanied with a decrease in TSH and body weight. All the previous effects were reversed by administration of either safranal or selenite in both regimens used.
Significant increases in hepatic MDA and NO levels were documented in thyrotoxic group which were decreased by administration of either safranal or selenite.
Thyrotoxic rats suffered a significant decrease in hepatic GSH level, SOD and catalase activities. These damaging effects were ameliorated by either safranal or selenite. L-T4 administration led to a significant upregulation in hepatic bax and caspase-9 and a downregulation in bcl-2 mRNA levels and these effects were reversed by either safranal or selenite. The upregulation in hepatic caspase-3 transcript level of thyrtoxic group did not achieve a statistical significance. Thyrotoxicosis led to a significant increase in hepatic DNA fragmentation % which was decreased by either safranal or selenite.
Histopathological examinations of liver tissue of animals treated with L-T4, revealed sever dialation and congestion in central vein with severe congestion in portal vein and dilation in bile duct and fibrosis accompanied with oedema in portal area. These deleterious effects were improved by administration of either safranal or selenite. The administration of safranal or selenite to healthy animals did not cause any histolopathological changes in liver.