Different levels of iodine intake and thyroid morphological changes of lactating rats and their newborns

Abstract

Objective To study the morphological and functional changes of thyroid in lactating rats and their offspring in iodine deficiency and iodine excess animal models.Methods One hundred and twenty Wistar rats(30 males and 90 females) were selected.Based on their body weight,the 90 females were stratified and randomly divided into five groups( 18 in each group):low iodine group 1 and group 2(fed with low iodine feed and deionized water containing iodine of 0,5 μg/L) ; high iodine group 1,group 2 and control group(feed with normal diet and deionized water containing iodine of 3000,10 000,50 μg/L).After fed for 3 month,all female rats were mated with males in a ratio of 3 ∶ 1.After birth for 10 days,8 female rats and their offspring in each group were sacrificed.Changes of thyroid were observed by naked eyes.The thyroid weight was measured and pathological changes of thyroids were observed under light microscope.Results ①Absolute and relative weight of lactating rats thyroid in low iodine group 1 and group 2 [ (92.02 ± 24.40 ),(77.11 ± 23.32 )mg,(0.509 ± 0.072),(0.384 ± 0.089) mg/kg] were much higher than that of control group[ (17.41 ± 9.25)mg,(0.102 ± 0.016)mg/kg,all P＜ 0.05].Absolute and relative weight of lactating rats thyroid in high iodine group 1 and group 2[(8.22 ± 0.41 ),(9.42 ±0.43)mg,(0.047 ± 0.006),(0.035 ± 0.005)mg/kg] were lower than that of control group(all P ＜ 0.05).Absolute and relative weight of lactating rats and their offspring thyroid was decreased with increase of iodide intake in the diet.②Thyroid enlargement of lactating rats in low iodine group 1 and group 2 was evident,but that of high iodine group 1 and group 2 was not.③Epithelial cell hyperplasia and smaller follicular cavity were observed in low iodine group 1 and group 2 under light microscope.Epithelial cell deformation and mostly flat were observed in high iodine group 1 and group 2.Conclusions Thyroid morphology is changed with iodide intake in the lactating rats and their offspring,and the changes are consistent between female rats and their newborns. Key words: Mammals; Rats; Iodine; Thyroid gland; Pathology