In our study, in the ovariectomized rats, which were characterized by increased body mass and insulin resistance, a reduced concentration of IL-18 was demonstrated and administration of estradiol caused an insignificant increase in the IL-18 concentration, while administration of sinapic acid (5 mg/kg) resulted in a strong tendency to increase the level of IL-18 in relation to the ovariectomized controls. The gene discussed is IL18; the disease is Insulin resistance.