The article reviewed dietary iodine reference intakes for different populations constituted by major countries and international organizations. Lowor high iodine intake can renderrisks to human health and there are different cut-points of iodineexcess for susceptible population. Universal salt iodization demonstratedthe influence on the spectrum of thyroid diseases and its benefitsoutweighrisks since its significant benefits on human potential and quality of life. This article has suggested practical evaluation indicators for certification of sufficient iodine intaketo keep adequate iodine intake for population.

The effects of different iodide intakes on the thyroid sodium iodide symporter (NIS) mRNA expression, thyroid hormones, urinary iodine and tissue iodine in thyroid were observed. NIS mRNA expression was elevated; and urinary iodine, thyroid tissue iodine and thyroid hormones were significantly lowered in low iodine group. In high iodine group, NIS mRNA expression was inhibited and thyroid hormones decreased. The results show that NIS is the important component of this autoregulatory mechanism. Both low and high iodine intakes can lead to hypothyroidism.

Objective:To study the master iodine nutrition status of population living in areas with different iodine in drinking water and the cut-off point of stopping iodized salt supply and the range of adequate iodine intake for the strategy of prevention from iodine deficiency or excess. Method:Thirteen townships points along the Yellow River downstream in Shandong were investigated and divided into six groups(A-F) based on water iodine concentrations of 0-50,50-100,100-150,150-300,300-800 and over 800 ?g/L. The indicators of water iodine,edible salt iodine,urinary iodine(UI) and thyroid goiter were observed. Results:From A,B,C,D,E and F group,the medians of water iodine concentration were 20.3,91.4,143.2,203.6,341.9 and 812.3 ?g/L,of edible salt iodine were 0,25.7,25.8,30.4,36.4 and 33.0 mg/kg,and of UI were 116.8,354.2,400.4,607.9,881.3 and 1 213.8 ?g/L respectively. The goiter rates were 10.8,8.6,15.0,14.2,14.9 and 25.0 % respectively . The sample proportion of UI below 100 ?g/L was 8.2%,of 100-300 ?g/L was 18.2% and of over 300 ?g/L was 73.6%. Frequency excursion of UI had a high trend towards water iodine concentration over 90?g/L in 5 groups. The proportion of UI over 300 ?g/L increased,consistent with higher water iodine level. Median UI of all groups with iodized salt decreased significantly,especially group F. There were significant correlations between UI and water iodine. Iodine nutrition status was markedly excessive in group B,C,D,E and F. Conclusions:Iodine nutrition status of most residents consuming drinking water with iodine concentration about 20 ?g/L should be adequately supplied with eligible iodized salt. Iodine intakes in groups B-F were excessive,and iodized salt supply should be stopped there. The cut-point of water iodine level where iodized salt stopped could possibly be 90 ?g/L,and the range of adequate iodine intake,in terms of drinking water,could be defined at range of over 20 to 90 ?g/L in iodine concentration.

The choline acetyltransferase (CHAT) and the molecular forms of acetyl-cholinesterase (ACHE) activites in various brain regions of 20-day-old hypothyroid and hyper-thyroid rats were measured. The results provided the following information: 1) CHAT and ACHE activities were directly interrelated with thyroid hormones. 2) In both hypothyroid and hyperthyroid rats the nonextractable ACHE activity was distinctly decreased in every brain region, suggesting that both conditions were affected in the critical period of cholinergic synaptic development. 3) The ratio of membrane-bound ACHE to soluble ACHE decreased;it showed that thyroid hormone deficiency might distrub development and maturation of cholinergic neurons. 4) In most regions of the central nervous system,the CHAT seemed to be more affected than ACHE by thyroid hormones.

FRTL cells were incubated in the culture medium containing 10 -6 -10-3 mol/L KI for 24, 48 and 72 h, and the levels of sodium iodide symporter (NIS) mRNA and protein were measured using RT-PCR and Western blot. The levels of NIS mRNA in FRTL cells incubated with different concentrations of iodide for 24 and 48 h showed no significant difference as compared with the control group, however, NIS protein was reduced gradually in FRTL cells incubated with different concentrations of iodide for 48 and 72 h as compared with that in control group. The higher the iodide concentration, the lower the levels of NIS protein. The results show that acute iodine excess does not affect the expression of NIS mRNA, but down-regulates NIS protein expression. Iodine excess may regulate the expression of NIS through post-transcription.

BACKGROUND: Triiodothyronine (T3) is an important regulation factor at the critical period of brain development. It maybe control the successive differentiation during the development of central nervous system (CNS).OBJECTIVE: To monitor the differentiation of neural stem cells (NSCs) induced by T3 and the thyroid hormone receptor (TR) mRNA expression changes.DESIGN: Open experiment.SETTING: Department of Pathology, Tianjin Medical College of Chinese People's Armed Police Force; Institute of Endocrinology of Tianjin Medical University.MATERIALS: This study was carried out in the Tianjin Medical University between January 2003 and March 2005.Ten-to-twelve-week-old aborted fetuses were obtained from the General Hospital of Tianjin Medical University with the approval of the local ethical committee. Informed consents were obtained from the mothers and their relatives.METHODS: ①Under the aseptic condition, the bilateral cortex of human fetal brain was removed and dissociated by brief mechanical trituration in D-Hanks. Then, 20 μg/L bFGF and 30 nmol/L T3 were used to induce the proliferation of NSCs and inoculated to poly-L-lysine-coated 24-well plate and 25 mL culture flask for routine culture at 1 ×109 L-1. The culture medium was DMEM/F12 serum-free complemented with N2. Half of the culture medium was changed every 48 hours.Seven days later, bFGF was discarded, only T3 was used for induction and differentiation. ② At 1, 2 and 3 weeks of culture, cells were collected, and RT-PCR was semiquantitatively used to detect TR mRNA expression changes at different stages of differentiation of NSCs. Isoforms were identified by immuocytochemistry.MAIN OUTCOME MEASURES: ①Cellular morphology observation and isoforms identification before and after differentiation of NSCs induced by T3. ② TR mRNA expression changes during the differentiation of NSCs.RESULTS: ①The hNSCs were round and had a smooth surface and gradually gathered to neurospheres. The proliferative hNSCs were nestin-positive and incorporated BrdU. When NSCs were induced by T3 for one week, most of the cells took on monopole or double poles, and had long and thin processes. The differentiated cells were neurofilament protein (NFP)-positive, galactocerebroside (GC)-positive or glial fibrillary acidic protein (GFAP)-positive. When NSCs were induced by T3 for three weeks, most of the cells were big, with unclear cell membrane, round nucleus, many thick processes which had many branches. The spider-like cells were scattered, and 80% of the cells were myelin basic protein-positive. ② TRα1 mRNA expression level was the highest before inducing NSCs. With the induction of T3, the expression level was decreased gradually, and was the lowest at 2 weeks, and then was rebounded gradually, but the final level was still lower than that of NSC (F =32.49, P =0.008). The tendency of TRα2 mRNA expression alteration was identical with that of TRα1 mRNA. TRβ1 mRNA expression level was the lowest in NSC, was increased gradually with the induction of T3 and attained the highest level at 2 weeks of induction of T3. Furthermore, the expression level of TRβ1 mRNA was also higher than that of TRα1 at the same time (t =15.64,P =0.001), and it reached the lowest level at 3 weeks of the induction. TRα3 expression level was firstly decreased after the differentiation induced by T3, and was close to the expression level of NSC at 2 weeks of induction (F =51.94, P =0.378), then was decreased to lower lever.CONCLUSION: T3 can induce NSC to differentiate into neurons, oligodendrocyte and astrocytes. TR mRNAs are expressed in different time intervals during the differentiation of NSCs.

Objective:To investigate the effects of exogenous hydrogen peroxide(H_2O_2)on mitochondrial superoxide production and mitochondrial membrane potential changes(△ψ)in fisher rat thyroid cell line(FRTL).Methods:Following 1 mmol/L H_2O_2 exposure in FRTL cells for 10 min,30 min and 24 h,mitochondrial superoxide production was measured by living cell imaging and flow cytometry using MitoSOX.The mitochondrial membrane potential was assayed by spectrofluorimeter and fluorescent microscopy using rhodamine 123(rh123).The cell viability was detected by MTT colorimetric method.Morphological changes were observed by invert microscope.Apoptosis assay was performed by acridine orange staining.Results:Quantitative measurements of the mean intensities of MitoSOX demonstrated significant increase with 1 mmol/L H_2O_2 following 10 min,30 min and 24 h treatment in FRTL cells compared with that of control.Fluorescence intensity of rh123 and optical density of MTr were significantly decreased in FRTL ceils with 1 mmol/L H_2O_2 following 30 min and 24 h treatment(P ＜ 0.01).Under light microscope and fluorescence microscope the characteristic morphological features of programmed cell death,pickuosis,karyorrhexis,and cell shrinkage were observed after acridine orange staining.Conclusion:Acute and chronic exogenous H_2O_2 exposure cause oxide stress in FRTL cells,which result in the increase of mitochondrial superoxide production,△ψdecline,cell necrosis and apoptosis.

Thyroid function ultimately depends on appropriate iodine supply to the gland. Thyroid hormone deiodination is an intrinsic component of the thyroid hormone homeostasis. Type Ⅰ iodothyronine deiodinase (D1) plays an important role in thyroid hormone metabolism and has close relationship with thyroid function. Based on successfully establishing animal models of iodine deficiency and iodine excess in Babl/c mice (Babl/c mice were randomly divided into five groups: low iodine (LI), normal iodine (NI), five-fold iodine (5HI) , ten-fold iodine (10HI) and fifty-fold iodine (50HI) group. Three months and six months after admistration, they were sacrificed and thyroids were excised), the expression level of D1 mRNA were examined by using real time quantitative PCR method. D1 activity was analyzed by 125I-rT3 as substrate combined with ion-exchange chromatography. The thyroid hormone was measured with radioimmunoassay method. The data revealed that in the case of iodine deficiency, both D1 mRNA expression and D1 activity was greatly increased(compared with NI groups, P

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.

Objective: To further investigate the effects of iodine intake on thyroid function and its possible mechanism. Method: Wistar rats were randomly divided into six groups: LI, NI, 5HI, 10HI, 50HI, 100HI. Different groups of rats were fed with feed and water of different iodine content. 3, 6 and 12 months after administration, they were sacrificed and thyroids were excised. The thyroid D1 mRNA expression level was determined by RT-PCR semi-quantitative method and the thyroid D1 activity was analyzed by using 125I-rT3 as substrate. Results: Compared with NI group, the thyroid D1 mRNA expression was decreased in all HI groups, and D1 activity was significantly higher in LI group and lower in HI groups. There was a tendency of decrease in D1 activity with increased doses of iodine intakes. Conclusion: In the case of iodine deficiency, thyroid D1 activity will increase greatly in order to convert more T4 to T3, but deficient iodine intake doesn’t improve thyroid D1 mRNA expression. Excess iodine can inhibit both thyroid D1 mRNA expression and its activity.