Effects Of Iodine Excess On Rat’s Bone Structure And Funcitons

Objective:1. To evaluate the effects of excessive iodine intake on rat’s thyroid funcitons and bone structure. 2. To evaluate the change of thyroid function in rat with excessive iodine intake, and the relationship with bone structure. 3. To explore the effects of iodine excess on osteoblast and osteoclast in rats. 4. To identify the adverse effects of iodine excess, providing more theoretical basis for the prevention and cure of iodine excess.Methods:Wistar rats, weaning one month, were randomly divided into 5 groups according to their sex and body weight, including normal iodine group(NI), five-fold high iodine group(5HI), ten-fold high iodine group(10HI), fifty-fold high iodine group(50HI) and one hunred-fold high iodine group(100HI). Iodine intake levels of 5 groups were 6.15μg/d, 30.75μg/d, 61.5μg/d, 307.5μg/d and 615μg/d, respectively. Urine iodine concentrations, body weight, body length and the femur length of rats were regularly measured. In 6-month and 12-month old rats, blood samples were taken from femoral artery and serum was segregated. Chemiluminescence was used to detect the levels of Free Triiodothyronine(FT3), Free Thyroxine(FT4) and Sensitive Thyroid Stimulating Hormone(s TSH). Radioimmunoassay was used to detect the levels Triiodothyronine(T3) and Thyroxine(T4). ELISA was used to detect serum BGP level. Execute rat, stripping the femoral, taking three point bending mechanics experiment.Results:1. Urine iodine concentrations in each HI group increased compared with NI group(P<0.05). 2. At 6th month, serum s TSH levels increased in HI groups, but there was no signifiacnt difference(P>0.05); At 12 th month, serum s TSH level rised in HI groups, but FT4 level decreased in male rats(P<0.05). 3. At 6th and 12 th month,, significant differences were found in the boold calcium content among male rats except 5HI group(P<0.05), while it was found significant differences only in NI and 10 HI group of female rats(P<0.05). At 6th and 12 th month, compared to the NI group, there was no statistical difference in the boold phosphorus content among male rats(P>0.05).But there was significant differences in the female in 100HI(P<0.05). And significant differences were found in the There was no statistical difference in ratserum BGP levels among different groups(P>0.05). 4. Both in 6th month with 12 th month, there was no signidicant difference in the diameter of femur(P<0.05),maximum deflection(P<0.05),maximum load(P<0.05),femoral maximum stress(P<0.05) compared HI groups to NI group. 5. The inspection of bone histomorphometry: Trabecular bone percentage and osteoblast percentage vary significantly among different groups(P<0.05). 6. At 6th month, compared to NI group, in high dose groups the bone trabecular number decreased and they became thin; the morphological structure split and curled, rank chaotically, the osteoid on the bone trabecular surface decreases, some of lost, marrow cavity broadened, osteoid reduced and fat vacuoles increased. As the extension of iodine intervention in time, the bone trabecular morphology changes even more significant, osteoid could not be observated. At 12 th month, the bone trabecular in 50 HI and 100 HI group become more sparse, defect seriously, result in bone fractured,the length of trabecular shorten, osteoid lacked obviously. 7. TRAP staining reveals irregular-shape, multinucleated giant osteoclasts, and cytoplasm staining in brick red. From 10 HI group on, osteoclasts get to change, the performance of TRAP(+) decreases in the number of multinucleated cells. In the 50 HI and 100 HI group, the above changes are especially obvious, the number of TRAP(+) multinucleated cells decreases, spreading limited, changes in female rats obviously, change trend in male is not obvious.Conclusion:1. Excessive iodine intake increases the risk of hypothyroidism. 2. The excessive iodine intake can cause the femoral microstructure change, resulting in long bone growth and metabolic abnormalities. 3. Overdose iodine can affect the activity of osteoblast and osteoclast, indicating that long-term iodine excess can cause endocrine type osteoporosisiodine, to cope with bone metabolic changes induced by iodine exess.