In Poland, a high level of nitrate and nitrite in food and iodine deficiency have been observed in the last years. The effects of potential goitrogens, namely allylisothiocyanate (SCN-), nitrate (NO3-) and nitrite (NO2-) on growth performance, serum hormones (fT4, TSH) and thyroid morphology were investigated in rats. Simultaneously, the potential antigoitrogenic effects of iodine and selenium supplements were studied. In experiment 1, male Wistar rats of an initial body weight of 95 g were fed four experimental diets, based on AIN93G diet for rodents, with 0 or 2 µg iodine (KIO₃) supplement per rat per day. The diets were: AIN-93G- control (C), AIN-93G + I (C+I), AIN-93G +SCN^- (6 mg/100 g body weight) (SCN), AIN-93G + SCN^- (6 mg/100 g body weight) + I (SCN+I), AIN-93G + NaNO₃ (300 mg/100 g) (NO₃), AIN-93G + NaNO₃ (300 mg/100 g) + I (NO₃+I), AIN-93G + NaNO₂ (25 mg/100 g) (NO₂) and AIN-93G + NaNO₂ (25 mg/100 g) + I (NO₂+I). The diets were fed to eight groups of rats (n=6) for 18 days. Feed intake was restricted to 15 g/day/rat. Body mass of rats was monitored weekly. On day 18, the rats were anaesthetised and their blood was drawn by cardiac puncture. The immulite rat TSH application kit was used to determine TSH concentrations in blood serum. Serum fT₄ was determined according to the LIA method. The thyroid glands were excised and processed by the conventional paraffin technique. The growth of rats was not affected by the intake of goitrogens. Serum fT₄ concentration tended to decrease by the treatments (C - 24.6, SCN-19.8, NO₃ - 21.8 and NO₂ - 21.3 pmol/L). At the same time, serum TSH levels were significantly increased after administration of SCN (p