碘缺乏和铁缺乏对大鼠甲状腺功能及定量形态学的影响

Effects of iodine deficiency and iron deficiency on thyroid function and morphology in rats

目的观察碘缺乏、铁缺乏以及碘铁联合缺乏对大鼠甲状腺功能及定量形态学的影响,为缺铁地区防治碘缺乏病提供新的思路和方法。方法 SPF/VAF级初断乳SD雄性大鼠48只,按体重随机分为对照组、碘缺乏组、铁缺乏组和碘铁联合缺乏组,每组各12只。通过饲料控制各组大鼠碘、铁摄入量,自由饮用去离子水。喂养8周后测定尿碘浓度;称取大鼠体重及甲状腺重量,计算甲状腺脏器系数;生化法检测全血血红蛋白;化学发光免疫分析法测定血清游离三碘甲腺原氨酸(FT3)、游离甲状腺素(FT4)和促甲状腺激素(TSH)水平。甲状腺经HE染色后光镜下观察,应用MIAS-2000型图像分析系统测量甲状腺滤泡平均直径、平均表面积、平均体积、体积密度、表面积密度、比表面积、数密度、球形因子等体视学指标。结果碘缺乏组、碘铁联合缺乏组大鼠尿碘中位数低于对照组、铁缺乏组(P<0.01)。与对照组相比,碘缺乏组和碘铁联合缺乏组大鼠甲状腺重量和脏器系数均增大,铁缺乏组体重下降、甲状腺脏器系数增大(P<0.05)。铁缺乏组、碘铁联合缺乏组全血血红蛋白低于对照组、碘缺乏组(P<0.05),铁缺乏组低于碘铁联合缺乏组(P<0.05)。碘缺乏组FT3高于对照组、铁缺乏组、碘铁联合缺乏组(P<0.05),碘铁联合缺乏组FT3低于碘缺乏组、高于铁缺乏组(P<0.05);FT4水平在对照组、铁缺乏组、碘缺乏组、碘铁联合缺乏组依次降低(P<0.05);碘缺乏组、碘铁联合缺乏组TSH高于对照组、铁缺乏组(P<0.05)。碘缺乏组、碘铁联合缺乏组甲状腺充血肿大、滤泡上皮细胞增生,铁缺乏组甲状腺略显苍白、滤泡上皮细胞无明显改变;碘缺乏组、碘铁联合缺乏组甲状腺滤泡平均直径、平均表面积、平均体积低于对照组,而表面积密度、比表面积、数密度高于对照组(P<0.05),铁缺乏组甲状腺滤泡体积密度大于碘缺乏组(P<0.05)。结论碘缺乏和铁缺乏均可降低甲状腺功能,前者作用较强,两者联合作用可增强效应;碘缺乏可引起小滤泡增生性甲状腺肿、胶质减少甚至缺如,铁缺乏对甲状腺形态学影响不明显。

Objective To observe the effects of iodine deficiency, iron deficiency and iodine-iron comitant deficiency on thyroid function and morphology in rats. Methods A total of 48 male healthy SPF/VAF weaning SD rats were randomly divided into four groups by body weight： normal （N） group, iodine deficiency （ID） group, iron deficiency （FD） group and iodine-iron comitant deficiency （IFD） group, 12 rats in each group. Rats of the four groups had free access to deionized water and diet was controlled to meet the iodine and iron intake requirement in each group. After eight weeks＇ feeding, the urine samples were collected and （NH4）2S2Os digesting, As3＋-Ce4＋ catalyzing spectrophotometry was used for estimation of urine iodine. Body weight and thyroid weight were measured, and thyroid organ coefficient was calculated. Blood was collected from the femoral artery and biochemical assay was used to measure hemoglobin. FT3, FT4 and TSH in serum were determined by chemiluminescence detection. Morphological observation of the thyroid follicle was performed by using routine histology method. Photos were taken under optical microscope and MIAS-2000 image analysis system was used to study stereological parameters, i.e. mean diameter （D）, mean surface （S）, mean volume （V）, volume density （Vv）, surface density （Sv）, specific surface （S/V）, numerical density （Nv） and spherical form （SF）. Results Medians of urine iodine in ID group and IFD group were significantly lower than those in N group and FD group, respectively （P〈0.01）. Compared with N group, rats in ID group and IFD group had significantly larger thyroid weight and thyroid organ coefficient, while rats in FD group had smaller body weight and larger thyroid organ coefficient （P〈0.05）. Rats in FD group and IFD group had lower hemoglobin compared with N group and ID group （P〈0.01）, and hemoglobin in FD group was lower than that in IFD group （P〈0.05）. Compared with ID group, levels of serum FT3 in N group, FD group and IFD group were lower （P〈0.01）. FT3 in IFD group was lower than that in ID group and higher than that in FD group, respectively （P〈0.05）. Serum FT4 in N group, FD group, ID group and IFD group decreased in order （P〈0.05）. Levels of TSH in ID group and IFD group were higher than those in N group and FD group （P〈0.05）. Thyroids of rats in ID group and IFD group demonstrated congestive enlargement and proliferation of follicular epithelial cells, while in FD group they turned to be pale and showd little change in epithelial ceils. Stereological parameters analysis results of thyroid follicles showed that D, S, V in ID group and IFD group were significantly lower while Sv, S/V, Nv were higher than those in N group （P〈0.01）. Vv in FD group was larger than that in ID group （P〈0.05）. Conclusion Both iodine deficiency and iron deficiency can reduce thyroid function while the former effect is stronger, and the combination of the two can make the reduction more obvious. Iodine deficiency produces hyperplasia goiter, while iron deficiency does not obviously change the morphology of thyroid follicle.