Establishment and application of reference interval for urinary iodine concentration/urinary creatinine ratio in early pregnancy / 中华内分泌代谢杂志

Objective:To explore the reference interval of urinary iodine concentration(UIC)/urinary creatinine(UCr) ratio evaluating the iodine nutritional status in early pregnancy women.Methods:A reference interval of UIC/UCr ratio was determined among 5 609 early pregnant women with normal thyroid function, negative thyroid autoantibodies, and no history of diseases or taking drug that may affect thyroid function. Then we verified the reliability of this reference interval in a group of 7 514 women in early pregnancy.Results:We determined the UIC/UCr ratio of 75-149 μg/g as the reference interval. In the reference interval, thyroglobulin antibody(TgAb), thyroid peroxidase antibody(TPOAb), and thyroglobulin(Tg) were all at lower levels, and the overall distributions were approximately U-shaped. The prevalence of thyroid dysfunction, the positive rates of antibodies and the proportion of Tg>40 μg/L were the lowest within the reference interval, while higher on both sides of the interval.Conclusion:The reasonable reference interval of the UIC/UCr ratio in iodine-sufficient regions is 75-149 μg/g in early pregnerty women.

The analysis of the changes of maternal thyroid autoantibodies during early pregnancy / 中华内分泌代谢杂志

Objective To investigate the changes and related factors of maternal thyroid autoantibodies during early pregnancy. Methods Urinary iodine concentration( UIC) , serum thyroid stimulating hormone( TSH) , free thyroxine ( FT4 ) , thyroid-peroxidase antibody ( TPOAb ) , thyroglobulin antibody ( TgAb ) concentrations were determined in 7 190 women during early pregnancy in an iodine-sufficient region of China. Results The prevalence of TPOAb positivity and TgAb positivity were 8. 7% and 12. 0% respectively. The prevalence of overt hypothyroidism and subclinical hypothyroidism increased significantly in group of thyroid antibody positivity. The prevalence of TPOAb positivity and TgAb positivity presented a U-shaped curve, ranging from mild iodine deficiency to iodine excess, especially increased significantly in the group with UIC<100 μg/L. Conclusion Prevalence of thyroid antibodies positivity became higher during early pregnancy. The positive thyroid autoantibodies during pregnancy were significantly associated with maternal hypothyroidism. Both iodine excess and iodine deficiency are risk factors of positive thyroid antibodies.

Iodine intake and thyroid function during pregnancy / 中华地方病学杂志

Iodine is an essential micronutrient for pregnant women,which affects thyroid function of pregnant women and fetus,and thus influences the intellectual development of offspring.Severe iodine deficiency could lead to overt hypothyroidism and fetal cretinism.In the areas implemented the universal salt iodization (USI) program,mild to moderate iodine deficiency and iodine excess may coexist during pregnancy.Iodine deficiency could lead to hypothyroxinemia in pregnant women.Iodine more than adequate and iodine excess could increase the prevalence of subclinical hypothyroidism.The effect of iodine supplementation on thyroid function in pregnant women with mild to moderate iodine deficiency may result in different conclusion.Therefore,it is important to maintain optimal urinary iodine concentration to prevent thyroid dysfunction.

Dynamic changes of thyroid function during gestation: A self-sequential longitudinal study / 中华内分泌代谢杂志

Objective To evaluate the trimester specific reference ranges and dynamic changes of thyroid functional indicators during gestation of healthy pregnant women.Methods According to the selection criteria,139 cases were selected as the normal pregnant population to establish a self-sequential longitudinal reference range.We collected samples eight times in every case throughout the gestation(including the 8th,12th,16th,20th,28th,36th week of prenatal,the 3rd and the 6th month postpartum) and detected the indicators of thyroid funciton.Meanwhile,301 healthy non-pregnant women of childbearing age were selected as the control group.Results The median of TSH was lowest in the first trimester,and then was increased in the second and third trimesters.The reference ranges of TSH were 0.20-4.01 mIU/L,0.43-3.97 mIU/L,and 0.57-3.96 mIU/L in the above trimesters.The free thyroxine (FT4) level from the 12th week of gestation to the 6th month of postpartum was gradually decreased and was lower than the non-pregnant level.The total thyroxine (TT4) was significantly increased at the 12th week of gestation and thereafter it was stable and returned to normal after childbirth.The free triiodothyronine(FT3) was gradually declined from the 12th week to the 28th week and returned to normal postpartum.Total triiodothyronine(TT3) was significantly increased at the 12th week and thereafter was stable,and returned to normal after childbirth.There was a significant negative correlation between TSH and FT4 in the first trimester(P＜0.01).There was no correlation between TSH and TT4 during the whole gestation.There were positive correlations between FT4 and TT4,FT3 and TT3 since the 12th week of gestation (P ＜ 0.01).Conclusions The gestational specific reference range of TSH based on the selfsequential longitudinal study was narrow,however,the upper limit was still higher than that recommended in foreign guidelines.

Dietary soy consumption during early pregnancy is not associated with the development of thyroid dysfunction / 中华内分泌代谢杂志

Data were collected through questionnaire from 505 women enrolled during early pregnancy.Based on soy intake frequency,the subjects were divided into three groups:frequent (three or more times per week),conventional ( more than twice per month but less than three times per week),and occasional ( two or fewer times per month).Serum TSH and FT4 were measured by chemiluminescence immunoassay.The urinary concentrations of two primary isoflavones (daidzein and genistein) and creatinine were further assessed in 95 subjects from the three groups.The percentages of frequent,conventional,and occasional consumers were 18.6％,62.6％,and 18.8％,respectively.No difference was found in age,medical records,family history of thyroid diseases,serum FT4,TSH,and prevalence of thyroid dysfunctions among three groups. Both urinary daidzein and genistein levels were significantly higher in the frequent consumers compared with the other two groups.No correlations were found between urinary isoflavone levels and serum FT4 or TSH.These findings suggest that dietary soy consumption during early pregnancy seems not to be associated with the development of thyroid dysfunction.

The Correlation between Thyrotropin and Dyslipidemia in a Population-based Study

This study investigated the relationship between serum thyrotrophin levels and dyslipidemia in subclinical hypothyroid and euthyroid subjects. A total of 110 subjects with subclinical hypothyroidism and 1,240 euthyroid subjects enrolled in this study. Patients with subclinical hypothyroidism had significantly lower high density lipoprotein cholesterol (HDL-C) levels than those who were euthyroid. The lipid profiles were each categorized and mean thyrotrophin levels were higher in subjects in the dyslipidemia subclasses than subjects in the normal subclasses. Thyrotrophin was positively associated with serum triglyceride and negatively associated with serum HDL-C in women. Thyrotrophin was also positively associated with total cholesterol (TC) in the overweight population along with TC and LDL-C in overweight women. In the euthyroid population, thyrotrophin was positively associated with TC in the overweight population. In conclusion, serum thyrotrophin was correlated with dyslipidemia in subclinical hypothyroid and euthyroid subjects; the correlation was independent of insulin sensitivity.

Relationship betweenserum TSH and dyslipidemia / 中华内分泌代谢杂志

Objective To investigate the relationship between serum thyrotrophin(TSH)and dyslipidemia in subclinical hypothyroid and euthyroid subjects. Methods An epidemiological study on diabetes and thyroid diseases was performed in Dadong community, Shenyang city, in 2007. 110 subjects with subclinical hypothyroidism(SCH)and 1 240 euthyroid subjects were enrolled in the study. Neither history of thyroid diseases nor administration of thyroid-related and lipid-regulating medicines were reported in these subjects. The levels of serum thyroid hormones, lipids, fasting plasma glucose(FPG), and insulin were determined. Results (1)Patients with SCH had significantly lower HDL-C levels than those who were euthyroid.(2)According to the guideline of treatment of adult dyslipidemia in China, the lipid profiles were each categorized. Mean TSH levels were higher in subjects in the dyslipidemia subclass than subjects in the normal subclass. The differences were significant in high LDL-C subclass in overweight individuals. In euthyroid overweight women, mean TSH levels were significantly higher in high LDL-C subclass. In the euthyroid population, TSH was positively associated with total cholesterol in overweight population. The association was not modified by the homestasis model assessment for insulin resistance(HOMA-IR)values.(3)TSH was associated positively with serum triglycerides and negatively with serum HDL-C in women. TSH was positively associated with total cholesterol in overweight population and positively associated with total cholesterol and LDL-C in overweight women after adjustment for age, sex, and body mass index. Conclusion Raised serum TSH seems to be a risk factor of dyslipidemia in subclinical hypothyroid and euthyroid subjects, which is independent of insulin sensitivity.

The reference range of serum thyrotropin in iodine-sufficient areas: An epidemiological study / 中华内分泌代谢杂志

Objective To verify the criteria proposed by National Academy of Clinical Biochemistry(NACB)guidelines in investigating the factors that affect serum TSH determination, and to determine the reference range of serum TSH in iodine-sufficient areas of China. Methods In 2007, 5 348 inhabitants were enrolled from 3 iodine-sufficient areas of Liaoning Province, and were asked to fulfill the questionnaire. Serum TSH, thyroid peroxidase antibody(TPOAb), and thyroglobulin antibody(TgAb)were determined, and thyroid ultrasonography was carried out. Results The distribution of TSH levels was skewed in healthy people and closely fit the curve of Gaussian distribution after logarithmic transformation. The levels of TSH in subjects of 12-19 years of age were significantly higher than those of other age groups(P＜0.01), and no significant difference was found among the latter groups. TSH level in females [(1.68±1.90)mIU/L] was higher than in males[(1.45±1.92)mIU/L, P＜0.01]. The reference range of TSH was 0.43-4.74 mIU/L in males, and 0.48-5.39 mIU/L in females. Family history of thyroid disease, abnormal thyroid ultrasonography, and positive thyroid antibodies were the factors that influenced TSH level. Conclusion The reference range of serum TSH in iodine-sufficient areas of China is established.