Higher Sensitivity to Thyroid Hormones May Be Linked to Maintaining the Healthy Metabolic Condition in People with Obesity: New Insight from NHANES.

INTRODUCTION: Obesity contributes to the pathogenesis of diverse metabolic diseases, yet the mechanism underlying metabolically healthy obesity (MHO) remains elusive. Thyroid hormones and sensitivity to them have a major impact on metabolism. Our study aimed to investigate the association between MHO and thyroid hormone sensitivity. METHODS: Thyroid hormone indices, including the thyroid-stimulating hormone (TSH) index (TSHI), the Thyrotroph Thyroxine Sensitivity Index (TTSI), the Thyroid Feedback Quantile-Based Index (TFQI), and the Parametric Thyroid Feedback Quantile-Based Index (PTFQI), were calculated based on a non-institutionalized US sample in the National Health and Nutrition Examination Survey (NHANES, 2007-2012). Participants were divided into four groups (metabolically healthy non-obesity [MHNO], metabolically unhealthy non-obesity [MUNO], MHO, and metabolically unhealthy obesity [MUO]) according to their body mass index and metabolic profiles. Linear regression, logistic regression, and restricted cubic splines were employed to analyze the association between thyroid hormone indices and metabolic phenotypes. RESULTS: A total of 4,857 participants (49.6% men; mean age, 42.6 years) were included, with 1,539 having obesity and 235 identified as MHO. Participants in the MHO group exhibited lower levels of TSH, TSHI, TTSI, TFQI, and PTFQI compared with the MHNO group (all p < 0.05), while the differences among MHNO, MUNO, and MUO groups were not statistically significant (all p > 0.05). Among participants with obesity, TSH, TSHI, TTSI, TFQI, and PTFQI were positively associated with metabolic abnormality (all p < 0.05). CONCLUSION: Participants with MHO exhibited higher thyroid hormone sensitivity among various obesity phenotypes, even when compared with those with MHNO. A positive association was observed between metabolic abnormality and thyroid hormone sensitivity, while the trend of TSH was observed to be consistent with sensitivity to thyroid hormone indices in discriminating metabolic abnormality. Hence, TSH has the potential to serve as a convenient index for detecting sensitivity to thyroid hormones and further metabolic conditions.

Comparison of six anthropometric measures in discriminating diabetes: A cross-sectional study from the National Health and Nutrition Examination Survey.

BACKGROUND: Traditional anthropometric measures, including body mass index (BMI), are insufficient for evaluating the risk of diabetes. This study aimed to evaluate the performance of new anthropometric measures and a combination of anthropometric measures for identifying diabetes. METHODS: A total of 46 979 participants in the National Health and Nutrition Examination Survey program were included in this study. Anthropometric measures, including weight, BMI, waist circumference (WC), waist-to-height ratio (WtHR), conicity index (CI), and A Body Shape Index (ABSI), were calculated. Logistic regression analysis and restricted cubic splines were used to evaluate the association between the anthropometric indices and diabetes. The receiver operating characteristic (ROC) curve analysis was performed to compare the discrimination of different anthropometric measures. RESULTS: All anthropometric measures were positively and independently associated with the risk of diabetes. After adjusting for covariates, the per SD increment in WC, WtHR, and CI increased the risk of diabetes by 81%, 83%, and 81%, respectively. In the ROC analysis, CI showed superior discriminative ability for diabetes (area under the curve 0.714), and its optimum cutoff value was 1.31. Results of the combined use of BMI and other anthropometric measures showed that among participants with BMI <30 kg/m2 , an elevated level of another metric increased the risk of having diabetes (P < .001). Similarly, at low levels of weight, CI, and ABSI, an elevated BMI increased diabetes risk (P < .001). CONCLUSIONS: WtHR and CI had the best ability to identify diabetes when applied to the US noninstitutionalized population. Anthropometric measures containing WC information could improve the discrimination ability.

MicroRNA-145-5p attenuates high glucose-induced apoptosis by targeting the Notch signaling pathway in podocytes.

MicroRNAs (miRNAs/miRs) are considered to serve essential roles in podocyte apoptosis, and to be critical in the development of diabetic nephropathy (DN). Activation of the Notch signaling pathway has been demonstrated to serve an important role in DN development; however, its regulatory mechanisms are not fully understood. The present study used a high glucose (HG)-induced in vitro apoptosis model using mouse podocytes. Expression levels of miR-145-5p and its target, Notch1, and other key factors involved in the apoptosis signaling pathway were detected and measured by reverse transcription-quantitative PCR and western blotting. A luciferase reporter assay was performed to elucidate the miRNA-target interactions. The functions of miR-145-5p in apoptosis were detected using flow cytometry and TUNEL staining. The present study demonstrated that in HG conditions, miR-145-5p overexpression inhibited Notch1, Notch intracellular domain, Hes1 and Hey1 expression at the mRNA and protein levels. Notch1 was identified as a direct target of miR-145-5p. Furthermore, cleaved caspase-3, Bcl-2 and Bax levels were reduced significantly by miR-145-5p overexpression. These results indicate that miR-145-5p overexpression inhibited the Notch signaling pathway and podocyte lesions induced by HG. In conclusion, the results of the present study suggested that miR-145-5p may be a regulator of DN. Additionally, miR-145-5p inhibited HG-induced apoptosis by directly targeting Notch1 and dysregulating apoptotic factors, including cleaved caspase-3, Bcl-2 and Bax. The results of the present study provided evidence that miR-145-5p may offer a novel approach for the treatment of DN.

Expression of pyruvate dehydrogenase is an independent prognostic marker in gastric cancer.

AIM: To investigate the expression and prognostic role of pyruvate dehydrogenase (PDH) in gastric cancer (GC). METHODS: This study included 265 patients (194 male, 71 female, mean age 59 years (range, 29-81 years) with GC who underwent curative surgery at the First Affiliated Hospital of China Medical University from January 2006 to May 2007. All patients were followed up for more than 5 years. Patient-derived paraffin embedded GC specimens were collected for tissue microarrays (TMAs). We examined PDH expression by immunohistochemistry in TMAs containing tumor tissue and matched non-neoplastic mucosa. Immunoreactivity was evaluated independently by two researchers. Overall survival (OS) rates were determined using the Kaplan-Meier estimator. Correlations with other clinicopathologic factors were evaluated by two-tailed χ(2) tests or a two-tailed t-test. The Cox proportional-hazard model was used in univariate analysis and multivariate analysis to identify factors significantly correlated with prognosis. RESULTS: Immunohistochemistry showed that 35.47% of total cancer tissue specimens had cytoplasmic PDH staining. PDH expression was much higher in normal mucosa specimens (75.09%; P = 0.001). PDH expression was correlated with Lauren grade (70.77% in intestinal type vs 40.0% in diffuse type; P = 0.001), lymph node metastasis (65.43% with no metastasis vs 51.09% with metastasis; P = 0.033), lymphatic invasion (61.62% with no invasion vs 38.81% with invasion; P = 0.002), histologic subtypes (70.77% in intestinal type vs 40.0% in diffuse type; P = 0.001) and tumor-node-metastasis (TNM) stage (39% in poorly differentiated vs 65.91% in well differentiated and 67.11% in moderately differentiated; P = 0.001) in GC. PDH expression in cancer tissue was significantly associated with higher OS (P < 0.001). The multivariate analysis adjusted for age, Lauren classification, TNM stage, lymph node metastasis, histological type, tumor size, depth of invasion and lymphatic invasion showed that the PDH expression in GC was an independent prognostic factor for higher OS (HR = 0.608, 95%CI: 0.504-0.734, P < 0.001). CONCLUSION: Our study indicated that PDH expression is an independent prognostic factor in GC patients and that positive expression of PDH may be predictive of favorable outcomes.

[The changes of thyrotropin level in euthyroid population: a 5-year follow-up study in communities with different iodine intakes].

OBJECTIVE: To determine the factors that influence the development of abnormal thyrotropin (TSH) level in an euthyroid population. METHODS: We conducted a follow-up study in 3 communities with different iodine status. Of the 3403 euthyroid subjects at baseline screened in 1999, 80.1% (n = 2727) was visited and sampled in 2004 for measuring TSH, thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb). RESULTS: Iodine status in the 3 communities were stable. Decreased TSH level (< 0.3 mU/L) developed in 2.5% (n = 68) of sampled subjects, while raised TSH level (> 4.8 mU/L) in 2.4% (n = 64). A logistic analysis showed that risk factors for developing decreased TSH level included positive conversion of TPOAb (OR = 5.5), positive TPOAb both in 1999 and in 2004 (OR = 4.0), positive TgAb in 2004 (OR = 3.7) and TSH < 1.0 mU/L in 1999 (OR = 2.6). Risk factors involved in developing raised TSH level included iodine status of Zhangwu community (OR = 4.1), iodine status of Huanghua community (OR = 3.9), positive TgAb in 2004 (OR = 3.7), positive TPOAb both in 1999 and 2004 (OR = 3.6), positive conversion of TPOAb (OR = 2.7) and TSH > 1.9 mU/L in 1999 (OR = 2.6). CONCLUSIONS: Exposure to long-term iodine excess imposes danger of developing hypothyroidism. The risk will be even higher when exposing to iodine adequacy after correction of iodine deficiency. An interval between 1.0 and 1.9 mU/L of TSH level was optimal with the least probability of developing abnormal TSH level.

[Epidemiological study of the effects of smoking cigarette on thyroid gland].

OBJECTIVE: To investigate the effect of cigarette smoking on thyroid gland volume, thyroid function and thyroid autoantibodies in the areas with different iodine intakes. METHODS: A cross-sectional epidemiological study in Panshan (mild iodine-deficient area), Zhangwu (more than adequate iodine intake area) and Huanghua (iodine-excessive area) was conducted in 3761 subjects in 1999.80.2 % of them were followed up in 2004. Questionnaires, thyroid function, thyroid autoantibodies, urinary iodine concentration,and thyroid B ultrasound were performed. RESULTS: The prevalence of goiter was higher in smokers than in non-smokers (15.1% vs. 11.5%, P< 0.05). The average thyroid volume was higher in smokers with phenomenon more obvious in Panshan and Huanghua areas. Data from logistic analysis showed that smoking cigarette was an independent risk factor of goiter. There was no difference in serum TSH and Tg level between smokers and non-smokers. The positive rate of TPOAb (>100 IU/ml) was higher in smokers than in non-smokers(10.8% vs. 9.0 % , P <0.05) and was especially obvious in Huanghua area. Smoking was a independent risk factor of increasing positive rate of TPOAb. During the prospective observation,it was found that the incidence of positive TPOAb(>,100 IU/ml) was 7.4% in the subjects that were from non-smokers turning to smokers and 2.9% in those whose smoking behavior did not change. Logistic analysis indicated that the shifting from non-smoking to smoking was independent risk factor for the increase on high incidence of positive TPOAb. CONCLUSION: Smoking cigarette was a independent risk factor of goiter. Smoking was also a risk factor of increasing TPOAb positive rate. Shifting from not smoking to smoking was an independent risk factor of increasing high incidence of positive TPOAb.

[Thyroid function and thyroid autoimmunity at the late pregnancy: data from 664 pregnant women].

OBJECTIVE: To study the prevalence of thyroid diseases, as well as characteristics of the disease spectrum and thyroid autoimmunity in women at the end of pregnancy. METHODS: Six hundred and sixty-four pregnant women (pregnancy group) and 276 non-pregnant women (control group) were enrolled in the study. Serum thyrotropin (TSH), thyroid peroxidase antibody (TPOAb), free T(3) (FT(3)) and free T(4) (FT(4)) were measured by high-sensitive immunochemiluminescent assay, and urinary iodine was also examined at the end of pregnancy. Overt hyperthyroidism was diagnosed when both TSH < 0.3 mU/L and FT(4) and/or FT(3) levels were elevated. Subclinical hyperthyroidism was diagnosed when TSH < 0.3 mU/L with normal FT(4) and FT(3) levels. The diagnostic criteria for overt hypothyroidism was TSH > 4.8 mU/L accompanied by decreased FT(4), and for subclinical hypothyroidism was TSH > 4.8 mU/L with normal FT(4) and FT(3) levels. RESULTS: (1) The median urinary iodine (MUI) of pregnancy group was 201.5 microg/L, and that of control group was 196.0 microg/L (P > 0.05). Women in the two groups were iodine-adequate. (2) The overall prevalence of thyroid diseases in pregnancy group and control group was 7.8% (52/664) and 6.9% (19/276), respectively (P > 0.05). (3) As for the diseases pattern, there were obvious differences between the two groups. In pregnancy group, the prevalence of hyperthyroidism was lower than that of hypothyroidism (1.1% vs 6.8%, P < 0.01). In control group, the prevalence of hyperthyroidism and hypothyroidism was 4.7% and 2.2%, respectively (P > 0.05). Compared with control group, the prevalence of hyperthyroidism in pregnancy group was much lower (1.1% vs 4.7%, P < 0.01), mainly due to the decrease of overt hyperthyroidism; whereas, the increment of subclinical hypothyroidism resulted in the higher prevalence of hypothyroidism in pregnancy group (6.8% vs 2.2%, P = 0.01). (4) The median TSH level of the healthy women in pregnancy group was significantly higher than that in control group (2.50 vs 1.54 mU/L, P < 0.01). The positive rate of TPOAb in pregnancy women was lower than that in non-pregnancy women (3.3% vs 9.4%, P < 0.01). CONCLUSION: At the end of pregnancy, hypothyroidism accounts for most thyroid diseases. Thyroid autoimmunity is suppressed.

[The dynamic changes of serum Th1 and Th2 cytokines in postpartum thyroiditis].

OBJECTIVE: To investigate the dynamic changes of serum Th1 and Th2 cytokines in patients with postpartum thyroiditis (PPT) during the first postpartum year. METHODS: 21 patients diagnosed as clinical PPT and 11 healthy postpartum women were enrolled in the study. Blood samples were taken before delivery and every 3 months postpartum for testing serum IFNgamma, IL-2, IL-4 and IL-10, which were measured with ELISA method. RESULTS: In patients with PPT, the detection rate of IFNgamma and IL-2 at 6th month postpartum were 19.0% (4/21) and 14.3% (3/21), respectively, being lower than those before delivery [52.4% (11/21) and 61.9% (13/21), respectively, P < 0.05]. The detection rate of IL-4 and IL-10 in patients were 71.4% (15/21) and 95.2% (20/21), respectively. A significant raise when compared with that before delivery (61.9%, 13/21) was seen in IL-10 (P < 0.05). Although Th1 cytokines (IFNgamma, IL-2) declined gradually post-parturition both in healthy postpartum women and PPT patients, yet Th2 cytokines (IL-4, IL-10) showed different tendency in healthy postpartum women and PPT patients. Th2 cytokines declined gradually in healthy postpartum women, while it kept at high level until the 12th month postpartum in the PPT patients. CONCLUSION: In PPT patients, Th2 cytokines show higher levels after delivery. Th2 cells are dominant and protected thyroids from Th1 cells during the course of PPT; this might be helpful to the recovery from disturbance of thyroid autoimmunity.

[Long-term effects of high iodine intake: inhibition of thyroid iodine uptake and organification in Wistar rats].

OBJECTIVE: To investigate the effects of chronic iodine excess on thyroid function, thyroid peroxidase (TPO) activity, and expression of sodium-iodide symporter (NIS). METHODS: 500 Wistar rats were randomly exposed to 4 doses of iodine 4 microg/d (G0, control), 6 microg/d (G1), 12 microg/d (G2), and 24 microg/d (G3) for 1, 2, 4 and 8 months. The urine iodine and tissue iodine was determined by arsenic/cerium catalyzing spectrophotograph. Radioimmunoassays were used to detect thyrotropin (TSH), free thyroxin (FT4), free triiodothyronine (FT3), total thyroxin (TT4), and total triiodothyronine (TT3). Guaiacol reaction method and potassium iodide oxygenation method were used to determine the activity of TPO. Suspension of single cells from thyroid tissue was made and the positive rate of NIS was determined by flow cytometry. The expression of NIS protein was assayed by immunohistochemistry. RESULTS: The urine iodine levels of G1, G2, and G3 were 1.5, 3, and 6 times of G0 respectively. FT4, FT3, and total iodine were found progressively accumulated in thyroid tissue with the elevation of iodine intake. The TPO activities of G2 and G3 at the 8th month were 0.17 +/- 0.04 and 0.15 +/- 0.03 respectively, both significantly lower than that of G0 (0.4 +/- 0.23, P < 0.05). The levels of iodine intake at different time points of G1-3 were significantly reduced in a iodine-dose dependent manner (r = -0.63 to -0.78, P < 0.01). The 131I intake at month 8 of G1, G2, and G3 were 56%, 49%, and 39% that of G0 respectively. At month 8 the NIS positive rates of G2 and G3 were significantly lower than that of G0 (both P < 0.05). The NIS protein positive rate was positively correlated with NIS protein expression intensity (r = 0.7-0.72, P < 0.01). The iodine content of thyroid tissue was negatively correlated with TPO activity, iodine intake rate, NIS protein positive rate and expression intensity (r = -0.62 to -0.88, P < 0.05). CONCLUSION: Moderate iodine excess continuously suppresses the thyroid iodine uptake and organification, which presents a mechanism for iodine-induced thyroid failure.

Effect of different iodine intake on schoolchildren's thyroid diseases and intelligence in rural areas.

BACKGROUND: Reports are increasingly appearing on the side effects caused by excessive iodine intake. Our objective was to find out whether iodine excess would impair the thyroid function and intelligence of schoolchildren in rural areas of China. METHODS: A comparative epidemiological study was made on thyroid function and intelligence of the schoolchildren in the areas of low, moderate or excessive intake of iodine. In the area of low intake of iodine (Panshan, Liaoning province, median urinary iodine (MUI) was 99 microg/L), of moderate intake of iodine (Zhangwu, Liaoning Province, MUI was 338 microg/L) and of excessive intake of iodine (Huanghua, Hebei Province, MUI was 631 microg/L). The numbers of schoolchildren from each area selected to take part in a Chinese version of Raven's Test were 190, 236 and 313, respectively, and then 116, 110 and 112 of them were tested for thyroid function, thyroid autoantibody (TAA) and urinary iodine (UI). RESULTS: There were no significant differences in the incidences of overt hyperthyroidism, subclinical hyperthyroidism and overt hypothyroidism in Panshan, Zhangwu and Huanghua. But significant differences were found in the incidences of subclinical hypothyroidism (P = 0.001) in these three areas. The incidences of subclinical hypothyroidism in Huanghua and Zhangwu were 4.76 and 3.37 times higher than that in Panshan. TAA were negative in all the schoolchildren with subclinical hypothyroidism except for one. No significant difference was found among the rates of thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) in these three areas. Mean serum thyroglobulin (TG) value of Huanghua was markedly higher than those of the other two (P = 0.02). Mean serum TG value of Zhangwu was higher than that of Panshan but the difference was not significant. Mean IQ value of the schoolchildren in Huanghua was markedly higher than that for Zhangwu (P = 0.001). Mean IQ value of the schoolchildren in Panshan was lower than that of Huanghua and higher than that of Zhangwu but, again, the differences were not significant. CONCLUSIONS: The increase of iodine intake may increase the risk for schoolchildren of subclinical hypothyroidism. In the area of iodine excess, most of the subclinical hypothyroidism cases are not of autoimmune origin. No obvious effect of excess iodine was found on mental development of schoolchildren.

[Multifactor analysis of relationship between the biological exposure to iodine and hypothyroidism].

OBJECTIVE: To assess the relationship between the biological exposure to iodine and hypothyroidism. METHODS: Logistic regression model was used to analyze the risk factors of hypothyroidism, according to the epidemiologic data of 3761 adults in 3 kinds of rural communities: mild iodine deficiency area (4 natural villages in Panshan County, Liaoning Province), more than adequate iodine (7 natural villages of Zhangwu County, Liaoning Province), and excessive iodine area (2 natural villages of Huanghua City, Hebei Province). RESULTS: More than adequate iodine and excessive iodine were independent risk factors of subclinical hypothyroidism (OR = 3.172 and 6.391, P < 0.05) and overt hypothyroidism (OR = 3.696 and 9.213, P < 0.05). When interactions of iodine exposure and thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb) were included, more than adequate iodine was still a risk factor of subclinical hypothyroidism (OR = 2.788, P < 0.01), but had no such effect on overt hypothyroidism. Interaction of more than adequate iodine and positive TgAb significantly affected subclinical hypothyroidism and overt hypothyroidism (OR = 2.656 and 3.347, P < 0.05). CONCLUSION: More than adequate and excessive iodine exposure are independent risk factors of hypothyroidism. The risk of hypothyroidism grows up and thyroid dysfunction becomes more serious with the increasing of the biological exposure to iodine.

[An epidemiological study on factors affecting serum thyroglobulin levels].

OBJECTIVE: To investigate the effects of several factors affecting serum thyroglobulin (TG) levels among people aged 14 or more. METHODS: We selected Panshan with median urinary iodine (MUI) 83.45 micro g/L as a deficient iodine intake community, Zhangwu with MUI 242.85 micro g/L as a sufficient iodine intake community and Huanghua with MUI 650.87 micro g/L as an excessive iodine intake community. Serum TG and thyroid stimulating hormone (TSH) were measured in 3,335 subjects whose thyroglobulin antibody (TGAb) were negative and thyroid volume were examined using B-ultrasound. RESULTS: In the population with MUI of 80 - 650 micro g/L, serum TG levels presented a "V" curve. An elevated serum TG was found in both the communities with deficient iodine intake and excessive iodine intake. The same trend was shown in the groups with different levels of serum TSH. An elevated serum TG was found in both the groups of TSH < 0.3 mU/L and TSH > 4.8 mU/L. The serum TG levels was positively correlated with thyroid volume and was higher in female subjects than in male. An increased serum TG was found in subjects of aged 50 in the community with deficient iodine intake. CONCLUSION: Serum TG level is affected by gender, amount of iodine intake, serum TSH level and thyroid volume.

[Effects of iodophor on the thyroid glands of female medical workers].

OBJECTIVE: To investigate the long-term effects of iodophor on thyroid function and autoimmunity in females. METHODS: 119 medical personnel who have been using iodophor as preoperative skin disinfectant more for than 2 years and 123 medical personnel who have not exposed to iodophor were studied. The urinary iodine, thyroid-stimulating hormone (TSH), free triiodothyronine (FT(3)), free thyroxine (FT(4)), thyroid peroxydase antibody (TPO-Ab) and TG-Ab in serum were measured and the thyroid were examined by B mode ultrasound apparatus. RESULTS: The median urinary iodine (MUI) was 300.4 micro g/L in the exposed group, not significantly higher than that in the non-exposed group (269.1 micro g/L, P > 0.05). The TSH levels of the exposed group and non-exposed group were 1.66 mU/L and 1.62 mU/L (P = 0.84). B mode ultrasound examination showed that the prevalence rate of thyroid disorders was 3.36% in the exposed group, not significantly different from that in the non-exposed group (2.44%). The thyroid autoantibody positive rate was not significantly different between these two groups too. The titer of autoantibody in the exposed group was 29.5 IU/L, significantly higher than that in the non-exposed group (22.4 IU/L, P = 0.048). The titer of TG-Ab in the exposed group was 21.85 IU/L, not significantly different from that in the non-exposed group (18.7 IU/L, P = 0.542). The mean titer of TPO-Ab in exposed group was 29.5 IU/L, significantly higher than that in non-exposed group (22.4 IU/L, P = 0.048). The total prevalence rate of all sorts of thyroid disorders in the exposed group was 11.76%, significantly higher than that in non-exposed group (4.07%, P = 0.026). The thyroid disorders discovered included clinical hyperthyroidism and subclinical hypothyroidism. CONCLUSION: Using iodophor as preoperative skin disinfectant may result in an increased incidence of thyroid disorders in female medical personnel. Medical personnel with iodophor exposure history should have their thyroid function and thyroid autoimmune status examined regularly.

[An epidemiological study on the relationship between selenium and thyroid function in areas with different iodine intake].

OBJECTIVE: To investigate the relationship between selenium status and thyroid dysfunction in 3 areas with different iodine intake. METHODS: An epidemiological research was performed in the rural communities of Panshan County (iodine-deficient area) and Zhangwu County (iodine-sufficient area), Liaoning Province, and Huanghua County, Hebei Province (iodine-excessive area). Serum selenium, TSH, FT3 and FT4 levels were examined in 329 patients with thyroid dysfunction (including clinical hypothyroidism, subclinical hypothyroidism, clinical hyperthyroidism and subclinical hyperthyroidism) and 183 normal inhabitants. RESULTS: The median serum selenium concentrations in Panshan, Zhangwu and Huanghua were 91.4, 89.1, and 83.2 microg/L respectively. There was no difference in serum selenium levels between the patients with subclinical hypothyroidism, clinical hypothyroidism, and clinical hyperthyroidism and their normal controls. The median serum selenium concentration of the subclinical hyperthyroidism patients was 82.6 microg/L, significantly lower than that of the normal controls (87.3 microg/L). The FT3/FT4 ratio was decreased, the FT4 level was increased in the subclinical hyperthyroidism patients in comparison with the normal controls, and no significant difference in FT3 level was found between them. No significant effect of sex and age was found on serum selenium level of normal inhabitants. In normal controls serum selenium was inversely correlated with serum TSH level, and the subjects with serum selenium < or = 80 microg/L had the median TSH level of 2.10 mU/L, markedly higher than that of the subjects with the serum selenium of 80-100 microg/L (1.29 mU/L) and that of the subjects with the serum selenium of 100 approximately 120 micro g/L (1.28 mU/L). For the thyroid dysfunction patients with positive thyroid auto-antibody (TPOAb) in Zhangwu County, the serum selenium was negatively associated with TPOAb level. The serum selenium level of the TPOAb highly positive group (TPOAb > 600 IU/ml) was 83.6 IU/ml, significantly lower than those of the TPOAb lowly positive group and TPOAb moderately positive group (83.6, 92.9 and 95.6 microg/L respectively). CONCLUSION: No obvious effect of selenium status is found on the development of thyroid dysfunction in these three areas. But selenium deficiency can impair thyroid function by means of disturbing thyroid hormone metabolism and decreasing antioxidant ability of the thyroid.