Iodine Nutrition and Thyroid Function in Pregnant Women Exposed to Different Iodine Sources

Biological Trace Element Research -     

Reply to: Iodine Nutrition and Thyroid Function in Pregnant Women Exposed to Different Iodine Sources

Biological Trace Element Research -     

甲状腺功能5 项检测在妊娠期妇女中的应用

目的:分析甲状腺功能5项检测在妊娠期妇女中的应用价值,为制定妊娠期妇女的甲状腺功能指标的参考值范围提供依据。方法:选取2013年8月~2014年12月我院收治的826例健康妊娠妇女(实验组)与794例非妊娠育龄妇女(对照组)为研究对象。采用电化学发光法检测甲状腺功能5项指标,即三碘甲腺原氨酸(TT3)、甲状腺素(TT4)、促甲状腺激素(TSH)、游离三碘甲腺原氨酸(FT3)、游离甲状腺素(FT4),比较两组甲状腺功能异常率,并比较5项指标在妊娠早、中、晚期妇女与对照组中的差异。结果:(1)实验组甲状腺功能异常的发生率(39.10%)显著高于对照组(17.63%),差异有统计学意义(P0.05);(2)实验组FT4、TT4水平随着妊娠期的进展逐渐降低,TSH水平逐渐升高,且均低于对照组水平,差异有统计学意义(P0.05);而各妊娠期FT3、TT3水平比较差异无统计学意义,但均略低于对照组(P0.05)。结论:甲状腺功能5项指标检测应作为妊娠期妇女的孕期必查项目之一,且制定早、中、晚期妊娠期妇女的甲状腺功能5项指标参考值范围十分必要。     

Urine Iodine Levels in Preeclamptic and Normal Pregnant Women

The aim of this study was to investigate the urine iodine concentration in women with severe preeclampsia and in healthy women in Erzurum, Turkey. Urine specimens were obtained from 40 severe preeclampsia and 18 healthy pregnant women. Urinary iodine levels were determined by the Foss method based on the Sandell–Kolthoff reaction. The urinary iodine level for women with severe preeclampsia was 4.25 ± 2.7 μg/dL, lower than 20.89 ± 6.4 μg/dL of urinary iodine for healthy pregnant women (p < 0.001). Blood magnesium concentration was found to be 1.63 ± 0.05 mg/dL for women with severe preeclampsia, which is lower than that of healthy pregnant women (1.87 ± 0.05 mg/dL; p < 0.001). There was a positive correlation between urinary iodine level and blood magnesium level in pregnant women with preeclampsia (Pearson correlation coefficient = 0.43; p < 0.01). However, there was no correlation between urinary iodine level and blood magnesium level in healthy pregnant women. There was no difference in thyroid hormone levels (T4, TSH, FT4) between women with severe preeclampsia and healthy pregnant women. However, there was a difference in T3 thyroid hormone levels between women with severe preeclampsia (1.86 ± 0.4 μg/dL) and healthy pregnant women (1.45 ± 0.3 μg/dL; p < 0.001). There was also a difference in FT3 between women with severe preeclampsia (2.77 ± 0.4 pg/mL) and healthy pregnant women (2.41 ± 0.5 μg/dL; p < 0.01). Urinary iodine excretion is currently the most convenient laboratory marker of iodine deficiency. The method is useful for the rapid and low-cost assessment of iodine deficiency. Our results suggested that urinary iodine concentration might be a useful marker for prediagnosing preeclamptic women. In addition, iodine supplementation may also be considered for preeclamptic therapy.     

妊娠期妇女甲状腺功能的筛查情况及相关影响因素分析

摘要 目的：了解妊娠期妇女甲状腺功能的筛查情况及相关影响因素。方法：以2016年1月~2017年1月在我院接受产前检查的400例孕妇为研究对象,其中早期妊娠78例、中期妊娠146例、晚期妊娠176例,同期健康体检合格妇女120例为对照组。比较妊娠妇女和对照组促甲状腺激素（TSH）、游离T3（FT3）及游离T4（FT4）水平,并分析妊娠合并甲状腺功能异常者妊娠不良结局发生情况,并分析妊娠合并甲状腺功能异常的影响因素。结果：400例孕妇中,亚临床甲减62例、临床甲减5例、亚临床甲亢16例、临床甲亢2例,甲状腺疾病合计85例。孕早期TSH低于孕中期及孕晚期,FT3浓度高于孕中期及孕晚期,FT4浓度高于孕中期及孕晚期,孕中期及孕晚期TSH水平高于对照组,孕中期及孕晚期FT3、FT4浓度低于对照组,差异有统计学意义（P<0.05）。不同年龄、流产次数、碘摄入量、吸烟组妊娠合并甲状腺功能异常率差异比较有统计学意义（P<0.05）。Logistic回归分析,年龄≥30岁、流产次数≥2次、碘摄入量≥150 μg/d为妊娠合并甲状腺功能异常发生的独立危险因素。妊娠合并甲状腺功能异常组妊娠不良结局合计率高于妊娠合并甲状腺功能正常组（P<0.05）。结论：加强对妊娠期妇女甲状腺功能的筛查和高危因素的管理能够预防不良妊娠结局,达到优生优育。     

Correlation Between Iodine Intake and Thyroid Function in Subjects with Normal Thyroid Function

Excessive iodine intake is known to induce hypothyroidism in people who have underlying thyroid disorders. However, few studies have been performed on subjects with normal thyroid function without a history of autoimmune thyroid disease. We hypothesized that high iodine intake may cause a subtle change in thyroid function even in subjects with normal thyroid function. We analyzed 337 subjects (64 men and 273 women; mean age, 49 years) who showed normal levels of thyroid peroxidase antibodies (TPO-Ab) and thyroglobulin antibodies (Tg-Ab) by measuring the urinary iodine excretion, free T4 (FT4), and thyroid-stimulating hormone (TSH). The results showed urinary iodine excretion had negative correlation with FT4 (γ = −0.11, p = 0.043) and showed a positive trend with TSH (γ = 0.10, p = 0.068). We found that 61.7% of subjects had circulating TPO-Ab within normal reference range. In all subjects, TPO-Ab levels were negatively correlated with FT4 (γ = −0.17, p = 0.002) and positively with TSH (γ = 0.13, p = 0.021). In conclusion, high iodine intake can negatively affect thyroid hormone levels in subjects with normal thyroid function. Population-based study will be helpful for further clarification.     

Oxidative Stress Increased in Pregnant Women with Iodine Deficiency

Iodine is an essential element trace for the synthesis of maternal thyroid hormones needed to support normal fetal development; it also acts as an antioxidant directly or induce antioxidant enzymes indirectly. Iodine deficiency and oxidative stress are associated with pregnancy complications. This study aimed to assess the urinary iodine concentration and its relationship with the antioxidant and oxidative stress status during gestation. Pregnant women were consecutively recruited from an obstetric clinic during all gestation trimesters, and urinary iodine concentration, antioxidant, and oxidative stress were determined. Results showed that 70 % of pregnant women have optimal iodine levels (150–200 μg/L), while approximately 30 % showed mild iodine deficiency (50–99 μg/L). Oxidative stress was significantly higher, and the antioxidant status was also compromised as evidenced by decreased total antioxidant status and superoxide dismutase (SOD) activity in pregnant women with mild iodine deficiency than pregnant women with optimal iodine levels. Significant positive correlations were noted between optimal iodine levels and total antioxidant status. Oxidative stress was significantly correlated with mild iodine deficiency. However, no significant correlation was found between iodine levels and SOD and catalase activities. In conclusion, for the first time, these data suggest a correlation between iodine levels and the antioxidant status during pregnancy.     

Determination of Reference Intervals of Ratios of Concentrations of Urinary Iodine to Creatinine and Thyroid Hormone Concentrations in Pregnant Women Consuming Adequate Iodine in Harbin,Heilongjiang Province

Biological Trace Element Research - The objectives of this study were to explore reference intervals of ratios of concentrations of urinary iodine to creatinine (UIC/UCr) in pregnant women, to...     

Association of Iodine and Iron with Thyroid Function

Iodine and iron are essential elements for healthy thyroid function. However, little is known about the association of iron and iodine with thyroid function in the general US population. We investigated iron and iodine status in relation to concentrations of thyroid hormones. We included 7672 participants aged 20 and older from three surveys (2007–2008, 2009–2010, and 2011–2012) of the National Health and Nutrition Examination Survey. Serum thyroid measures (including free and total T3 and T4, and TSH), serum iron concentration, and urinary iodine concentrations were measured. Multivariate linear regression models were conducted with serum thyroid measures as dependent variables and combinations of serum iron concentration and urinary iodine concentration as predictors with covariate adjustment. Logistic regression models were performed with TSH levels (low, normal, and high) and combinations of serum iron concentration and urinary iodine concentration. Overall, 10.9% of the study population had low iron; 32.2 and 18.8% had low or high iodine levels, respectively. Compared with normal levels of iron and iodine, normal iron and high iodine were associated with reduced free T3 and increased risk of abnormal high TSH. Combined low iron and low iodine was associated with reduced free T3 and increased TSH. In addition, high iodine was associated with increased risk of abnormal high TSH in females but not in males. Thyroid function may be disrupted by low levels of iron or abnormal iodine, and relationships are complex and sex-specific. Large prospective studies are needed to understand the mechanisms by which iron interacts with iodine on thyroid function.     

Iodine, Selenium, and Other Trace Elements in Urine of Pregnant Women

The purpose of this work was to determine trace element levels in urine and evaluate possible associations between urinary iodine concentration (UIC), other trace elements (Cr, Cu, Fe, Mn, Na, Se, Zn), toxic elements (Cd, Pb), anthropometrical measures (body weight and height), glycemic indices (serum insulin and glucose), and several parameters related to thyroid function (thyroid stimulating hormone, free thyroxine, antithyroid peroxidase antibodies, thyroid volume, and thyroid echogenicity) in pregnant women. One hundred sixty-nine participants were recruited. The whole study group, originating from Krakow region, comprised three subgroups belonging to three trimesters: I trimester (n?=?28), II trimester (n?=?83), and III trimester (n?=?58). Trace elements were determined using inductively coupled plasma mass/(atomic emission) spectrometry. Partial least square model was used to reveal correlation structure between parameters investigated, as well as a possible causal relationship between dependent parameters and potentially explanatory parameters. Results obtained for trace and toxic elements in urine were comparable with results of other authors, although the study group was not homogenous. We confirmed (1) low iodine excretion in pregnant women, (2) the existence of statistically significant correlation between UIC and urinary selenium, and (3) lack of correlation between latter parameter and typical indices of thyroid function. Urinary selenium correlated with other urinary trace elements, but physiological significance of this finding remains uncertain. The fact that a large number of pregnant women fail to meet dietary recommendations for iodine is the major reason for concern.     

Thyroid Function in Patients Treated with Radioactive Iodine for Thyrotoxicosis

A series of 105 patients treated at least two years earlier with radioactive iodine for thyrotoxicosis have been surveyed. Eighty-five patients (81%) were euthyroid clinically and on the basis of routine thyroid function tests. Of the euthyroid patients 46 (54%) had normal thyroid-stimulating hormone (TSH) levels and 39 (46%) had raised TSH levels. There was no difference in serum triiodothyronine levels between these two groups but the serum protein bound iodine and serum thyroxine, though still well within the normal range, were significantly lower in the group with raised TSH levels. The serum cholesterol was also significantly higher in this latter group.Most of the euthyroid patients were seen again a year later. None had become hypothyroid and neither those with normal nor those with raised TSH levels showed any evidence of a decline in the level of serum thyroxine.It is concluded that raised serum TSH levels in patients treated with iodine-131 are not necessarily indicative of hypothyroidism. There is no indication that patients who have this abnormality become overtly hypothyroid over a 12-month follow up.     

Safe Range of Iodine Intake Levels: A Comparative Study of Thyroid Diseases in Three Women Population Cohorts with Slightly Different Iodine Intake Levels

Iodine excess may lead to thyroid diseases. Our previous 5-year prospective survey showed that the prevalence and incidence of hypothyroidism or autoimmune thyroiditis increased with iodine intake. The aim of the present study was to investigate the optimal range of iodine intake by comparing the prevalence of thyroid diseases in three areas with slightly different levels of iodine intake. In 2005, 778 unselected women subjects from three areas with different iodine intake levels were enrolled. Levels of serum thyroid hormones, thyroid autoantibodies, and urinary iodine were measured, and thyroid B ultrasounds were performed. Among the subjects with mildly deficient iodine intake, those with adequate intake, and those with more than adequate intake, the prevalence of clinical and subclinical hypothyroidism was 0, 1.13, and 2.84%, respectively (P = 0.014); that of thyroid goiter was 24.88, 5.65, and 11.37%, respectively (P < 0.001); that of serum thyrotropin values was1.01, 1.25, and 1.39 mIU/l, respectively; and that of serum thyrotropin/thyroglobulin ratio was 7.98, 6.84, and 5.11, respectively (P < 0.001). In conclusion, median urinary iodine 100~200 μg/l may reflect the safe range of iodine intake levels. Serum thyrotropin/thyroglobulin ratio might be a better index of evaluating iodine status.     

Assessment of Iodine Status in Children,Adults, Pregnant Women and Lactating Women in Iodine-Replete Areas of China

Background

Iodine deficiency disorders (IDD) are widespread in China. Presently, IDD have been put under control by Universal Salt Iodisation (USI) in China; however, there is a lack of evidence on whether the iodine status in adults, pregnant women and lactating women is optimal. This study was therefore conducted to assess the iodine nutrition and thyroid function of children, adults, pregnant women and lactating women residing in areas where the USI program is fully established.

Design

Six areas were selected according to the geographical regions in China. In each of these areas, we selected 4 distinct groups of subjects (children, adults, pregnant women and lactating women) in regions where the coverage rate of iodised salt was more than 95% and the levels of iodine and fluoride in drinking water were less than or equal to 10 µg/L and 1 mg/L, respectively. We tested the iodine content of salt, urinary iodine (UI), free thyroxin (FT4), thyrotropin (TSH), thyroglobulin (Tg), thyroglobulin antibody (Tg-Ab) and antimicrosomal antibody (TM-Ab) in the 4 groups, and examined the thyroid volume in children.

Results

The median urinary iodine (MUI) concentrations were 271.4 μg/L, 260.2 μg/L, 205.9 μg/L and 193.9 μg/L in children, adults, pregnant women and lactating women, respectively; MUI in children and adults were more than adequate. The goitre prevalence (GP) in children was 6.70%. The odds ratios (OR) of subclinical hypothyroidism in the Tg-Ab- or TM-Ab-positive groups were 3.80, 7.65, 2.01 and 7.47 for children, adults, pregnant women and lactating women, respectively, compared with the negative groups.

Conclusions

The iodine status in children and adults is above the requirement, we should reduce their iodine intake. Subclinical hypothyroidism easily occurs in the Tg-Ab or TM-Ab positive groups.     

自身免疫性甲状腺功能紊乱孕妇血清TPOAb 检测的临床价值

目的:探讨血清甲状腺过氧化物酶抗体(TPOAb)对于患有自身免疫性甲状腺功能紊乱的孕妇的临床诊断价值。方法:筛选2009年9月至2013年1月我院收治的205例孕妇,其中甲状腺功能紊乱孕妇55例(紊乱组),非甲状腺功能紊乱孕妇150例(非紊乱组);非紊乱组中,年龄30岁的高龄孕妇50例(高龄组),年龄≤30岁的孕妇100例(正常组)。采用化学发光法,测定所有孕妇血清中游离甲状腺三碘原氨酸(FT3)、游离甲状腺素(FT4)、促甲状腺激素(TSH)和TPOAb水平。结果:紊乱组患者血清中TSH、TPOAb及TPOAb阳性率水平显著高于非紊乱组,且存在统计学意义(均P0.05),而两组患者血清中FT3和FT4水平无统计学意义(均P0.05);高龄组和正常组血清中TSH、FT3、FT4及TPOAb水平均无统计学意义(均P0.05);与TSH正常组相比,TSH异常组中约有超过半数TPOAb表现为阳性,有统计学意义(P0.05);孕妇体内的TSH水平正常与否,均有出现TPOAb阳性的可能,在TSH水平较高(4.67 m IU/L)中,TPOAb阳性概率更高。结论:TSH、FT3、FT4水平正常而TPOAb呈阳性的孕妇依然存在自身免疫性甲状腺功能紊乱的可能性,监测TPOAb的水平对于妊娠期孕妇功能紊乱的诊断与治疗具有重要意义。     

甲状腺疾病对孕妇及胎儿的影响

目的:甲状腺功能障碍是孕期比较常见的内分泌疾病,本次研究的主要目的是找出孕期最常见的甲状腺功能障碍以及对孕妇及胎儿的影响及结果。方法:回顾性分析我院2006年1月1日至2009年1月1日在我院行产前保健的中孕期孕妇1000例。详细记录各项检查结果,TSH水平检测,TSH筛查异常的孕妇测定其游离T4水平并详细记录直至胎儿出生。结果:甲状腺功能障碍孕期比较常见,其中孕妇合并亚临床甲状腺功能减退(6.40%)和临床甲状腺功能减退(4.40%)最为常见,合并临床甲状腺机能减退症的产妇更容易发生妊娠期高血压(20.5%)和TUGR(13.6%),患有亚临床甲状腺机能减退症和亚临床甲状腺机能亢进症的产妇发生贫血的几率比较大,分别为14.1%和22.2%,并且有统计学意义。临床甲状腺机能亢进的产妇发生妊娠期糖尿病的风险明显增高33.3%,亚临床甲状腺机能减退症的产妇因胎儿宫内窘迫而行剖宫产的几率明显增高(23.4%,p<0.05),而且发生早产的风险同样增加9.4%。结论:甲状腺功能障碍孕期常见,尤其是及亚临床甲状腺功能减退(6.40%)。对孕妇及胎儿的不利影响比较明显,孕前检测甲状腺功能极为必要。     

Hypocalcemia in Pregnant Women

The objective of this study is to estimate the prevalence of hypocalcemia and its correlation with dietary intake of calcium (DICa) and urinary calcium excretion (UCaE) in pregnant women. Healthy pregnant women (n = 543) were enrolled consecutively. DICa was calculated form dietary history. Serum calcium (SCa) and 24-h UCaE was measured. Student t test and Chi-square tests were used to compare the continuous and categorical data in women with and without hypocalcemia (SCa ≤ 8.7 mg/dL). Linear regression was applied for determining the independent variables for hypocalcemia. The age and gestation (mean ± SD) were 21.9 ± 2.5 years and 18.0 ± 3.5 weeks, respectively. The body mass index (BMI; mean ± SD) was 23.3 ± 3.9 kg/m². Seventy-one percent women had an education of less than 10 years. The DICa and SCa were 325 ± 198 mg and 8.1 ± 1.5 mg/dL, respectively. The prevalence of hypocalcemia was 66.4% (362/545); all being asymptomatic. There was no significant difference in women with and without hypocalcemia in terms of weight, BMI, monthly family income, DICa, UCaE, and their obstetric outcome. Daily dietary calcium intake was less than the recommended dietary allowances. There was a high prevalence of asymptomatic hypocalcemia in pregnant women of low socio-economic status which was unrelated to their overall nutritional status and daily calcium intake. It did not have any adverse effect on the immediate pregnancy outcome.