The effect of insulin-like growth factor-I on thyroid morphologic change of mice with iodine deficiency and iodine excess

Objective To study the expression level of thyroid insulin-like growth factor-Ⅰ (IGF-Ⅰ) in iodine deficiency and excess mice and the effect of thyroid gland IGF-Ⅰ in the thyroid morphological change. Methods Forty-eight Balb/c mice were chosen as studied objects,weighing about 16 g. They were divided into three groups: low iodine(LI,iodine content of 50 μg/kg in feed,drinking deironized water) group,normoi(NI,iodine content of 300 μg/kg in feed,drinking deironized water) group and high(HI,iodine content of 300 μg/kg in feed,iodoine of content 14 700 μg/kg in drinking) group,16 mice in each group. Mice were put to death after 12 weeks and taken out of their thyroid gland. The body weight,absolute and relative weights of thyroid gland were measured and the morphological change of thyroid gland were observed under microscope. The expression levels of thyroid gland IGF-Ⅰ mRNA and protein were detected by RT-PCR and immunohistochemistry,respectively. Results There were statistical significances between groups of thyroid absolute and relative weights(F = 315.881,405.921,all P 0.05). The brownish particles of LI group were more than NI and HI groups in the thyroid follicle epithelium by immunohistochemistry,while HI group was less than NI group. Conclusions The mice of iodine deficiency presented follicular hyperplasia goiter,the mice of iodine excess presented colloid accumulative goiter. The change of IGF-Ⅰ mRNA and protein expression may participate morphologleal change,indicating autocrine IGF-Ⅰ of thyroid gland may play an important role in regulating goiter formation. Key words: Iodine deficiency; Iodine excess; Mice; Thyroid gland; Insulin-like growth factor Ⅰ