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Objective:To observe the urinary iodine content (UIC), breast milk iodine content (BMIC) and milk iodine excretion of lactating rats under different iodine nutrition levels, and to explore the iodine metabolism of the lactating rats under different iodine nutrition levels.Methods:Forty female Wistar rats with body weight ranging from 70 to 120 g were divided into low iodine (LI) group, normal iodine (NI) group, hight iodineⅠ (HIⅠ) group and hight iodine Ⅱ (HIⅡ) group according to body weight by random number table method, with 10 rats in each group. The rats were fed low-iodine diet, and the iodine ion concentration of drinking water in each group was 0, 325, 18 700 and 37 450 μg/L. Twenty male rats were fed according to the feed method of NI group. After 8 weeks of intervention, the male and female rats were caged and mated in a ratio of 1 ∶ 2. Milk and 24 h urine were collected on the 7th, 14th and 21st days of lactation (L7, L14 and L21), and the amount of food and drinking water consumed were recorded. The 24 h milk excretion was calculated by acute lactation test. UIC and BMIC were determined by inductively coupled plasma mass spectrometry (ICP-MS).Results:The 24 h total iodine intake of lactating rats in LI, NI, HIⅠ and HIⅡ groups were (1.84 ± 0.51), (30.51 ± 6.79), (765.95 ± 317.41) and (1 654.26 ± 560.55) μg/d, respectively. The difference between groups was statistically significant ( P < 0.001). At L7, L14 and L21, there were statistically significant differences in UIC, BMIC and milk iodine excretion at the same lactation stages among different groups ( P < 0.001). In HIⅡ group, the difference of BMIC and milk iodine excretion at different lactation stages (L7, L14, and L21) were significantly signrficant ( P < 0.05). The 24 h milk iodine excretion of LI, NI, HIⅠ and HIⅡ groups was (1.23 ± 0.85), (11.88 ± 5.23), (207.09 ± 114.51), (493.67 ± 242.47) μg, respectively. The proportion of 24 h milk iodine excretion to 24 h total iodine intake was 66.85%, 38.94%, 27.04% and 29.84%, respectively. Conclusions:About 39% of dietary iodine is supplied to offspring through milk when iodine nutrition is normal. The iodine excretion ratio of milk is increased or decreased with low and high iodine levels. These results indicate that lactating rats with different iodine nutrition levels can regulate the ratio of iodine excretion in milk through their own compensatory effect to reduce the influence of iodine deficiency and iodine excess on their offspring.
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To explore the influences of pregnancy and iodine intake on thyroid function and immune functions, 210 pregnant women and 290 fertile women were chosen from iodine excess area, and the average ages of them were (27. 69±4. 73 )and (30. 62±6. 01 )years respectively. Fasting blood and urine were collected in the morning. The urinary iodine level was determined by arsenic-cerium catalytic contact. Serum free triiodothyronine ( FT3 ), free thyroxine ( FT4 ), and sensitive thyroid-stimulating hormone ( sTSH ) levels were measured by chemiluminescence.Thyroid peroxidase antibody (TPOAb)and thyroglobulin antibody (TGAb)were measured by radioimmunoassay. The median urinary iodine in the pregnant and fertile women were I 240. 70 and 949. 21 μg/L, respectively. There were 84. 3% pregnant women and 81.0% fertile women admitting excess iodine intake. The prevalence of overall thyroid diseases was 22. 9% in the pregnant women and 30. 3% in the fertile women. The prevalence of hyperthyroidism,subclinical hyperthyroidism, hypothyroidism, and subclinical hypothyroidism was0. 5%, 1.9%, 0. 5%, and 20. 0% in the former group, and 2. 8%, 0. 3%, 0. 3%, and 26. 9% in the latter. Both FT3 and FT4 levels of the pregnant women were lower than those of fertile women [(4. 03±0. 59 vs 4. 71 ± 1.04)pmol/L, ( 13. 35 ± 1.59 vs 14. 27 ±3.63 )pmol/L,both P＜0. 01], and the positive rate of TGAb of pregnant women was also lower than that of fertile women (7. 1% vs14. 1%, P=0. 014). The prevalence of thyroid diseases and positive rate of thyroid autoantibodies is high in women with excess iodine intake. Compared with fertile women, pregnancy may lead to decreas~s in level of thyroid hormones and positive rate of TGAb. Their iodine intake should be controlled, and the thyroid function and autoimmunity antibodies should be monitored.
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Objective:To observe the effect of different iodine intake on the thyroid function in euthyroid adult persons.Methods:One hundred and sixty-one euthyroid healthy volunteers aged 18-24 years were randomly divided into 7 groups.Each group was assigned to receive 500 μg,750 μg,1 000 μg,1 250 μg,1 500 μg,and 2 000 μg iodide/day for four weeks.Serum concentrations of free triiodothyronine(FT3),free thyroxin(FT4)and sensitive thyroid-stimulating hormone(sTSH)were measured by chemolumineseenee assays.Results:Serum FT3 concentration was found a small decline within the normal range in all the iodide supplemented groups(P ＜ 0.05).The level of FT4 was significantly lower,when the dose was up to 1 500 μg (P ＜ 0.05).The level of serum sTSH was increased after 2 weeks iodide supplement in all groups,and after 4 weeks in 500 μg and 750 μg groups(P ＜ 0.05).No significant changes were observed in FT3,FT4 and sTSH between groups(P＞ 0.05).Conclusion:The thyroid function of normal people showed a rise in serum sTSH at a short time and a high-dose of iodine intake.
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Objective To explore the effects of different levels of selenium nutrition on thyroid function,liver deiodinase type Ⅰ(DⅠ) and brain deiodinase type Ⅱ(DⅡ) activities in experimental autoimmune thyroiditis (EAT) rats. Methods A total of 32 female Lewis rats were randomly divided into four groups that included control group,model group,EAT with selenium-supplementation group and EAT with selenium-deficiency group. After two weeks of the basal diet administration,the rats were fed on forage containing different levels of selenium for nine weeks and the total intake of selenium were 4,4,40 and 0.4 ?g/d,respectively. The rats of model group,EAT with selenium-supplementation group and EAT with selenium-deficiency group were induced to establish the model of experimental autoimmune thyroiditis from the third week to eighth week. The pathological change of thyroid was examined,and the levels of selenium in the blood,serum thyroid autoantibody and thyroid hormone,DⅠ and DⅡ activities were measured simultaneously. Results Compared with control group,thyroid autoantibody and thyroid hormone levels significantly increased in model group,EAT with selenium-supplementation group and EAT with selenium-deficiency group (P
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Objective To explore the safety of iodine intake in adults.Method Euthyroid healthy volunteers aged 18 to 24 years(22.54?2.65y)were adopted and divided into 7 groups randomly.Each group was assigned to receive 500,750,1000,1250,1500,and 2000?g iodide oral doses daily for 4 w.Blood and urine samples during morning fast were obtained on weeks 0,2 and 4.We used chemiluminescence immunoassay(CLIA) to measure sTSH,FT4 and immunoradiometric assay(IRMA) to measure TPOAb and TGAb.Urinary iodine was evaluated.The dietary survey was done by recording method to collect food consumption data for 7 d.We also measured the iodine amount in drinking water,food and iodinized salt.Results All the volunteers were in adequate iodine levels.The median urinary iodine was 272.25?g/L,and the dietary iodine intake including iodinized salt was 346.24?g/d.We found all the iodide supplemented groups responded in the same way with a significant rise in urinary iodide excretion and in serum sTSH levels,with a small decline in serum FT4 concentration at normal range.After 2 w the serum sTSH levels in the iodide supplemented groups increased nearly more than double,and nearly two fold after 4 w.The subclinical hypothyroidism appeared at 500～2000 ?g/d after 2 w.After 4 w the prevalence of subclinical hypothyroidism kept the same level at 500?g/d(15%),and increased at other iodine supplemented groups. The subclinical hypothyroidism prevalence at the 750-2000?g/d doses was at the range of 28.00%～47.37%.No clinical hypothyroidism was observed among the people during iodide administration.Conclusion The dysfunction of thyroid in normal population was mainly subclinical hypothyroidism with an exposure to a high dose iodine intake(500?g～2000?g) in a short time.It can lead to subclinical hypothyroidism in the subjects at 500?g /d doses.In iodine-sufficient area iodine supplemented dose was not appropriate to exceed 500?g/d.We suggested the UL of iodine below 900 ?g/d.