The present study was designed to investigate the effects of levothyroxine and carbimazole on body weight gain, liver functions, and histology of female rats. Rats were divided into three groups (12 rats/group), with each group divided into two sub-groups (6 rats/group) based on the period of treatment for three and six weeks At the end of the study, the rate of body weight gain of hyperthyroid rats exhibited a significant decrease after three and six weeks. The rate of body weight gain of hypothyroid female rats displayed a significant decrease after three weeks only. Liver to body weight ratio (L/BW) of hyperthyroid rats displayed a significant increase after three and six weeks. However, (L/BW) of hypothyroid rats manifested no significant change and a significant decrease, respectively after three and six weeks of study versus control. The rate of food consumption was different in the three groups and even in the same group at different times. The liver function tests were found changed in both hyper- and hypothyroid female rats. The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of both hyper- and hypothyroid rats displayed a significant increase after three and six weeks. Reduced glutathione (GSH) levels exhibited a significant decrease after three weeks and a significant increase after six weeks. On other hand, GSH of the hypothyroid rats displayed no significant change after three and six weeks. The present study also showed a histopathological damage in liver of either hyper- or hypothyroid rats. These results suggested that both hyper- and hypothyroidism induced adverse effects on liver physiology and histology in female rats.