Thyrotoxicosis is hypermetabolic clinical syndrome resulting from elevations in thyroid hormonal level, especially free thyroxin (T4), triodothyronine (T3), or both. This study was applied to investigate the different metabolic effect of experimental thyrotoxicosis on one hundred white male albino rats. Rats were divided into two main groups. The first one was the control, comprised 30 rats, receive no drugs and experimental group included 70 rats received L-thyroxine (50 mg/kg B.W) daily for 4 weeks. Blood samples for serum separation were collected from all animal groups four times at 1, 2, 3, 4 weeks from onset of thyrotoxicosis induction. The obtained results revealed that an increased in thyroglobulin- antibody, thyroid peroxidase antibody, calcium and sodium, urea, uric acid and LDL-c concentration. Also ALT, AST, alkaline phosphates, LDH, CPK and Ck- MB activity were significantly increased. On the other hand, serum potassium, phosphorus, magnesium, serum cholesterol and high density lipoprotein HDL-c were significantly decrease in all experimental group when compared to control. From the obtained results it could be concluded that thyrotoxicosis causes changes in metabolism of lipids, carbohydrate, minerals and enzymatic activity of the body.