This study was designed to investigate the effect of thyroid hormone disturbance on lipids profiles and liver functions. Eighteen mature male rats Rattus norvegicus were divided into three groups. The first and the second groups were injected subcutaneously with thyroxine (T4) and carbimazol (both at 600 µg/kg BW) respectively on alternate days, to produce recurrent periods of hyper and hypothyroidism .The control group which is the third group was injected with physiological saline. The process continued 4 weeks, after that, injection, blood specimens were collected to estimate serum levels of T3 and T4, Total cholesterol (TC), Triglycerides (TG), High density lipoprotein cholesterol (HDL-C), Low density lipoprotein cholesterol (LDL-C) and Very low density lipoprotein cholesterol (VLDL-C) were determined in the serum. In addition to that, we measure GOT, GPT and CPK enzymes activity. The results showed no significant difference in body weight and a significant increase (P<0.01) in liver weight of Thyroxine injected group, while Carbimazol injected group showed significant increase (P<0.05) in body and in liver weight. There was a significant decrease in TC concentration and there was no significant decrease in TG, HDL-C, LDL-C and VLDL-C concentration in the serum of Thyroxine injected group, while the Carbimazol injected group showed significant increase in serum TC, LDL-C, TG, HDL-C and VLDL-C concentration. The results also pointed to a significant increase in GOT and GPT activity, and no significant decrease in CPK activity in the serum of thyroxine injected group, in addition to a significant increase in GPT activity and a significant increase in GOT activity without any significant differences in CPK activity noticed in the liver homogenate of the same group. The results also pointed to a significant increase in GOT and GPT activity, and significant increase in CPK activity in the serum of Carbimazol injected group, with significant decrease in GOT activity, significant decrease in GPT activity and significant increase in CPK activity in the liver homogenate of the same group. Results of the liver histological study showed changes in the liver histological structure in both groups. An increasing in T3 and T4 levels led to a little expansion in the sinusoids and this might be due to accumulation of glycoprotein, also there was a centrilobular hepatocytes necrosis and congestion with RBCs in the sinusoids of central area due to hypoxia especially in perivenular hepatocytes area. In addition to extravasations of RBCs between the hepatocytes which are severely atrophied and some are necrosed. It was noticed that there is a direct relationship between low levels of T4 and T3 and the hepatic dysfunction which led to sinusoids expansion, granular and hydropic degeneration due to hepatocytes immunological or toxically damaged which gave the hepatocytes edema appearance.
