In an experiment with 405 Hisex white hens rations with 5–20 % low glucosinolate rapeseed (RS) or rape‐seed meal (RSM) of 00 quality were used. Feed intake, egg production, individual egg weight and live weight gain were reduced in hens fed 5–20% RS and 10–20% RSM. There was a positive correlation between the RS proportion in the ration and the thyroid weight as well as the iodine content of the thyroid. The relation between the iodine content related to one gram of thyroid and the RS proportion was not significant. There were not any significant differences between the RSM groups and the iodine content of the thyroid. The T3and T4concentrations in the blood plasma was independent of the RS‐ or RSM‐proportion in the diet.