Thyroid Volume in Pregnancy is Associated with Parity, Gestational Age, and Body Mass Index in an Iodine-sufficient Area.

OBJECTIVE: We compared thyroid volume (TV) and presence of nodular goiter (NG) in pregnant vs. non-pregnant women in an iodine-sufficient area. We also evaluated the relationship between gestational age, parity, and TV in the pregnant women group, and determined the 2.5th and 97.5th percentiles of normal TV in pregnancy. METHODS: This cross-sectional study included 299 healthy women (216 pregnant) without previous thyroid diseases. Thyroid ultrasounds were performed and compared between pregnant and non-pregnant women. The range of normal distribution of TV (2.5th and 97.5th percentiles) in pregnancy was determined after excluding individuals with positive thyroid antibodies, NG, and/or abnormal serum thyrotropin (TSH) or free thyroxine (FT4). RESULTS: Thyroid volume was larger among pregnant compared to non-pregnant women (8.6 vs 6.1 cm3; p < 0.001) and was positively correlated with gestational age (rs = 0.221; p = 0.001), body mass index (BMI, rs 0.165; p = 0.002), and FT4 levels (rs 0.118 p = 0.021). Nodular goiter frequency did not differ between the two groups. There was a negative correlation between TV and TSH (rs -0.13; p = 0.014). Thyroid volume was lower among primiparous compared to multiparous patients (7.8 vs 8.9; p < 0.001) and was positively correlated with parity (rs 0.161; p = 0.016). The 2.5th and 97.5th percentiles of TV were 4.23 and 16.47 cm3, respectively. CONCLUSION: Thyroid volume was higher in pregnant compared to non-pregnant women and was positively related to parity, BMI, and gestational age in a normal iodine status population. Pregnancy did not interfere with the development of NG.

OBJETIVO: Comparamos o volume tireoidiano (VT) e a presença de bócio nodular (BN) em mulheres grávidas e não grávidas em uma área suficiente em iodo. Também avaliamos a relação entre idade gestacional, paridade e VT no grupo de gestantes e determinamos os percentis 2,5 e 97,5 de VT normal na gestação. MéTODOS: Este estudo transversal incluiu 299 mulheres saudáveis (216 grávidas) sem doenças tireoidianas prévias. Ultrassonografias de tireoide foram realizadas e comparadas entre mulheres grávidas e não grávidas. A faixa de distribuição normal de VT (percentis 2,5 e 97,5) na gestação foi determinada após a exclusão de indivíduos com anticorpos tireoidianos positivos, BN e/ou tireotropina sérica (TSH) ou tiroxina livre (T4L) anormais. RESULTADOS: O VT foi maior entre as gestantes em comparação com as mulheres não grávidas (8,6 vs 6,1 cm3; p < 0,001) e foi positivamente correlacionado com a idade gestacional (rs = 0,221; p = 0,001), índice de massa corporal (IMC, rs 0,165; p = 0,002) e níveis de T4L (rs 0,118 p = 0,021). A frequência de BN não diferiu entre os dois grupos. Houve correlação negativa entre VT e TSH (rs -0,13; p = 0,014). O VT foi menor entre as primíparas em comparação com as multíparas (7,8 vs 8,9; p < 0,001) e foi positivamente correlacionado com a paridade (rs 0,161; p = 0,016). Os percentis 2,5 e 97,5 de VT foram 4,23 e 16,47 cm3, respectivamente. CONCLUSãO: O VT foi maior em gestantes em comparação com mulheres não grávidas e foi positivamente relacionado à paridade, IMC e idade gestacional em uma população com status iódico normal. A gravidez não interferiu no desenvolvimento de BN.

Thyroid Volume in Pregnancy is Associated with Parity, Gestational Age, and Body Mass Index in an Iodine-sufficient Area / O volume tireoidiano em gestantes está associado à paridade, idade gestacional e índice de massa corporal em uma área suficiente em iodo

Abstract Objective We compared thyroid volume (TV) and presence of nodular goiter (NG) in pregnant vs. non-pregnant women in an iodine-sufficient area. We also evaluated the relationship between gestational age, parity, and TV in the pregnant women group, and determined the 2.5th and 97.5th percentiles of normal TV in pregnancy. Methods This cross-sectional study included 299 healthy women (216 pregnant) without previous thyroid diseases. Thyroid ultrasounds were performed and compared between pregnant and non-pregnant women. The range of normal distribution of TV (2.5th and 97.5th percentiles) in pregnancy was determined after excluding individuals with positive thyroid antibodies, NG, and/or abnormal serum thyrotropin (TSH) or free thyroxine (FT4). Results Thyroid volume was larger among pregnant compared to non-pregnant women (8.6 vs 6.1 cm3; p< 0.001) and was positively correlated with gestational age (rs = 0.221; p= 0.001), body mass index (BMI, rs 0.165; p= 0.002), and FT4 levels (rs 0.118 p= 0.021). Nodular goiter frequency did not differ between the two groups. There was a negative correlation between TV and TSH (rs -0.13; p= 0.014). Thyroid volume was lower among primiparous compared to multiparous patients (7.8 vs 8.9; p< 0.001) and was positively correlated with parity (rs 0.161; p= 0.016). The 2.5th and 97.5th percentiles of TV were 4.23 and 16.47 cm3, respectively. Conclusion Thyroid volume was higher in pregnant compared to non-pregnant women and was positively related to parity, BMI, and gestational age in a normal iodine status population. Pregnancy did not interfere with the development of NG.

Resumo Objetivo Comparamos o volume tireoidiano (VT) e a presença de bócio nodular (BN) em mulheres grávidas e não grávidas em uma área suficiente em iodo. Também avaliamos a relação entre idade gestacional, paridade e VT no grupo de gestantes e determinamos os percentis 2,5 e 97,5 de VT normal na gestação. Métodos Este estudo transversal incluiu 299 mulheres saudáveis (216 grávidas) sem doenças tireoidianas prévias. Ultrassonografias de tireoide foram realizadas e comparadas entre mulheres grávidas e não grávidas. A faixa de distribuição normal de VT (percentis 2,5 e 97,5) na gestação foi determinada após a exclusão de indivíduos com anticorpos tireoidianos positivos, BN e/ou tireotropina sérica (TSH) ou tiroxina livre (T4L) anormais. Resultados O VT foi maior entre as gestantes em comparação com as mulheres não grávidas (8,6 vs 6,1 cm3; p< 0,001) e foi positivamente correlacionado com a idade gestacional (rs = 0,221; p= 0,001), índice de massa corporal (IMC, rs 0,165; p= 0,002) e níveis de T4L (rs 0,118 p= 0,021). A frequência de BN não diferiu entre os dois grupos. Houve correlação negativa entre VT e TSH (rs -0,13; p= 0,014). O VT foi menor entre as primíparas em comparação com as multíparas (7,8 vs 8,9; p< 0,001) e foi positivamente correlacionado com a paridade (rs 0,161; p= 0,016). Os percentis 2,5 e 97,5 de VT foram 4,23 e 16,47 cm3, respectivamente. Conclusão O VT foi maior em gestantes em comparação com mulheres não grávidas e foi positivamente relacionado à paridade, IMC e idade gestacional em uma população com status iódico normal. A gravidez não interferiu no desenvolvimento de BN.

Consequences of Iodine Deficiency and Excess in Pregnancy and Neonatal Outcomes: A Prospective Cohort Study in Rio de Janeiro, Brazil.

Background: Insufficient or excessive iodine intake during gestation may compromise adaptive mechanisms in maternal thyroid function and lead to adverse pregnancy outcomes. In this context, we aimed to study the effects of maternal iodine status in the first and third trimesters of gestation on obstetric and neonatal outcomes in an iodine-sufficient population in Rio de Janeiro, Brazil. Methods: A total of 214 pregnant women in the first trimester of gestation were enrolled and prospectively followed until delivery between 2014 and 2017. All participants were ≥18 and ≤35 years, had a spontaneous single pregnancy, and had no history of thyroid or other chronic diseases, nor were they taking iodine-containing supplements at enrollment. In the first trimester, we obtained clinical information and determined thyroid function and the urinary iodine concentration (UIC) of the participants. Thyroid function and UIC were reassessed in the third trimester. Iodine status was determined by the median of UIC obtained from six urine spot samples by the inductively coupled plasma mass spectrometry method. Pregnancy and neonatal outcomes and delivery information were obtained from medical records. Results: The median UIC in the whole population was 219.7 µg/L. The prevalence of UIC <150 µg/L was 17.2%, and 38.7% had UIC ≥250 µg/L. Gestational diabetes (GDM) was higher in the group with UIC 250-499 µg/L (n = 77) compared with the group with UIC 150-249 µg/L (n = 94) (20.3% vs. 9.7%, p < 0.05). Ultimately, UIC ≥250 µg/L was an independent risk factors for GDM (relative risk [RR] = 2.9 [confidence interval, CI = 1.1-7.46], p = 0.027) and hypertensive disorders of pregnancy (HDP) (RR = 4.6 [CI = 1.1-18.0], p = 0.029). Among 196 live-born newborns, lower birth length was observed in infants whose mothers had UIC <150µg/L (n = 37) in the first trimester compared with those with UIC 150-249 µg/L (n = 86) (median interquartile range: 48.0 [2.2] vs. 49.0 [4.0] cm, p = 0.01). Maternal UIC <150 µg/L was negatively associated with birth length of newborns (Exp (B) = 0.33 [CI = 0.1-0.9], p = 0.03). Conclusions: In a population whose median iodine intake is sufficient, extensive individual variation occurs. Such abnormalities are associated with increased GDM and HDP when UIC is ≥250 µg/L, and lower infant birth length when UIC is <150 µg/L.

Selective case finding versus universal screening for detecting hypothyroidism in the first trimester of pregnancy: a comparative evaluation of a group of pregnant women from Rio de Janeiro.

Objective Maternal hypothyroidism during pregnancy may lead to adverse outcomes. Recently published guidelines by the American Thyroid Association (ATA) do not advocate for universal screening but recommend a case-finding approach in high-risk pregnant women. The present study aims to evaluate the accuracy of this approach in identifying women with thyroid dysfunction during early pregnancy. Subjects and methods This is a multiple-center, cross-sectional study. Three hundred and one pregnant women were enrolled. Anamnesis and a physical examination were performed to detect which women fulfilled the criteria to undergo laboratory screening of thyroid dysfunction, according to the ATA's 2017 guidelines. The Zulewski's validated clinical score was applied to assess signs and symptoms of hypothyroidism. Serum levels of thyrotropin (TSH), free thyroxine (FT4), anti-thyroperoxidase (TPO-Ab), and anti-thyroglobulin (Tg-Ab) antibodies were determined. Results Two hundred and thirty one women (78%) were classified as high risk, and 65 (22%) were classified as low risk for thyroid dysfunction. Regarding the clinical score, 75 patients (31.2%) presented mild symptoms that were compatible with SCH, of which 22 (7.4%) had symptoms as the only risk factor for thyroid disease. 17 patients (5.7%) had SCH, of which 10 (58.8%) belonged to the high-risk group, and 7 (41.2%) belonged to the low-risk group. OH was found in 4 patients (1.4%): 3 (75%) in the high-risk group and 1 (25%) in the low-risk group. Conclusions The ATA's proposed screening criteria were not accurate in the diagnosis of thyroid dysfunction in pregnancy. Testing only the high-risk pregnant women would miss approximately 40% of all hypothyroid patients.

Variation of iodine status during pregnancy and its associations with thyroid function in women from Rio de Janeiro, Brazil.

OBJECTIVE: To assess iodine status and its effects on maternal thyroid function throughout pregnancy. DESIGN: In the present prospective cohort study, three urinary samples were requested for urinary iodine concentration (UIC) determinations in both the first and third gestational trimesters. Serum thyrotropin (TSH) and free thyroxine (FT4) were analysed in both trimesters and thyroid antibodies were assessed once. SETTING: Rio de Janeiro, Brazil.ParticipantsFirst-trimester pregnant women (n 243), of whom 100 were re-evaluated during the third trimester. RESULTS: Iodine sufficiency was found in the studied population (median UIC=216·7 µg/l). The first- and third-trimester median UIC was 221·0 and 208·0 µg/l, respectively. TSH levels (mean (sd)) were higher in the third trimester (1·08 (0·67) v. 1·67 (0·86) mIU/l; P<0·001), while FT4 levels decreased significantly (1·18 (0·16) v. 0·88 (0·12) ng/dl; P<0·001), regardless the presence of iodine deficiency (UIC<150 µg/l) or circulating thyroid antibodies. UIC correlated (ß; 95% CI) independently and negatively with age (-0·43; -0·71, -0·17) and positively with multiparity (0·15; 0·02, 0·28) and BMI (0·25; 0·00, 0·50). Furthermore, median UIC per pregnant woman tended to correlate positively with TSH (0·07; -0·01, 0·14). Women with median UIC≥250 µg/l and at least one sample ≥500 µg/l throughout pregnancy had a higher risk of subclinical hypothyroidism (OR=6·6; 95% CI 1·2, 37·4). CONCLUSIONS: In this cohort with adequate iodine status during pregnancy, excessive UIC was associated with an increased risk of subclinical hypothyroidism.

Recent recommendations from ATA guidelines to define the upper reference range for serum TSH in the first trimester match reference ranges for pregnant women in Rio de Janeiro.

OBJECTIVES: American Thyroid Association (ATA)'s new guidelines recommend use of population-based trimester-specific reference range (RR) for thyrotropin (TSH) in pregnancy. The aim of this study was to determine first trimester TSH RR for a population of pregnant women in Rio de Janeiro State. SUBJECTS AND METHODS: Two hundred and seventy pregnant women without thyroid illness, defined by National Academy of Clinical Biochemistry, and normal iodine status were included in this sectional study. This reference group (RG) had normal median urinary iodine concentration (UIC = 219 µg/L) and negative anti-thyroperoxidase antibodies (TPOAb). Twin pregnancy, trophoblastic disease and use of drugs or supplements that influence thyroid function were excluded. In a second step, we defined a more selective reference group (SRG, n = 170) by excluding patients with thyroiditis pattern on thyroid ultrasound and positive anti-thyroglobulin antibodies. This group also had normal median UIC. At a final step, a more selective reference group (MSRG, n = 130) was defined by excluding any pregnant women with UIC < 150 µg/L. RESULTS: In the RG, median, 2.5th and 97.5th percentiles of TSH were 1.3, 0.1, and 4.4 mIU/L, respectively. The mean age was 270 ± 5.0 and the mean body mass index was 25.6 ± 5.2 kg/m2. In the SRG and MSRG, 2.5th and 975th percentiles were 0.06 and 4.0 (SRG) and 0.1 and 3.6 mIU/L (MSRG), respectively. CONCLUSIONS: In the population studied,TSH upper limit in the first trimester of pregnancy was above 2.5 mIU/L. The value of 3.6 mIU/L, found when iodine deficiency and thyroiditis (defined by antibodies and ultrasound characteristics) were excluded, matches recent ATA guidelines.

Recent recommendations from ATA guidelines to define the upper reference range for serum TSH in the first trimester match reference ranges for pregnant women in Rio de Janeiro

ABSTRACT Objectives: American Thyroid Association (ATA)'s new guidelines recommend use of population-based trimester-specific reference range (RR) for thyrotropin (TSH) in pregnancy. The aim of this study was to determine first trimester TSH RR for a population of pregnant women in Rio de Janeiro State. Subjects and methods: Two hundred and seventy pregnant women without thyroid illness, defined by National Academy of Clinical Biochemistry, and normal iodine status were included in this sectional study. This reference group (RG) had normal median urinary iodine concentration (UIC = 219 μg/L) and negative anti-thyroperoxidase antibodies (TPOAb). Twin pregnancy, trophoblastic disease and use of drugs or supplements that influence thyroid function were excluded. In a second step, we defined a more selective reference group (SRG, n = 170) by excluding patients with thyroiditis pattern on thyroid ultrasound and positive anti-thyroglobulin antibodies. This group also had normal median UIC. At a final step, a more selective reference group (MSRG, n = 130) was defined by excluding any pregnant women with UIC < 150 μg/L. Results: In the RG, median, 2.5th and 97.5th percentiles of TSH were 1.3, 0.1, and 4.4 mIU/L, respectively. The mean age was 270 ± 5.0 and the mean body mass index was 25.6 ± 5.2 kg/m2. In the SRG and MSRG, 2.5th and 975th percentiles were 0.06 and 4.0 (SRG) and 0.1 and 3.6 mIU/L (MSRG), respectively. Conclusions: In the population studied,TSH upper limit in the first trimester of pregnancy was above 2.5 mIU/L. The value of 3.6 mIU/L, found when iodine deficiency and thyroiditis (defined by antibodies and ultrasound characteristics) were excluded, matches recent ATA guidelines.

Iodine status of pregnant women from a coastal Brazilian state after the reduction in recommended iodine concentration in table salt according to governmental requirements.

OBJECTIVE: To evaluate iodine status among pregnant women from a coastal state after Brazilian governmental resolution reducing iodine concentrations in table salt. Secondarily, we correlated urinary iodine concentration (UIC) with thyroid volume and hormones. METHODS: Inductively coupled plasma mass spectrometry was used to assess UIC from 629 samples of 244 first trimester pregnant women. Thyroid ultrasound, serum thyroglobulin, thyrotropin, free thyroxine, and antithyroid antibodies were measured as iodine concentrations on samples of table salt from patient's home. RESULTS: Median UIC was adequate (221.0 µg/L); however, 48.7% of women had insufficient (<150 µg/L), and 4.5% excessive UIC (≥500 µg/L) in at least one sample. UIC was independently and negatively correlated with age (ß: -0.58; 95% confidence interval [CI], -0.89 to -0.27) and positively with multiparity (ß: 0.20; 95% CI, 0.04-0.34). In those without thyroiditis, UIC tended to be positively correlated with body mass index (P = 0.098) and thyrotropin (P = 0.072). Independent variables associated with iodine insufficiency were age >30 y (odds ratio [OR] = 2.0; 95% CI, 1.2-3.2) and obesity (OR = 0.2; 95% CI, 0.2-0.7). Excessive UIC was associated negatively with age (OR = 0.2; 95% CI, 0.04-0.8) and positively with multiparity (OR = 2.5; 95% CI, 1.0-6.0) and subclinical hypothyroidism (OR = 5.6; 95% CI, 1.0-30.2). CONCLUSION: This population has iodine sufficiency, and supplementation should not be generally considered, based on the risk association between excessive UIC and subclinical hypothyroidism.