A disfunção tireoidiana durante a gestação cursa com maior morbidade materno-fetal. A deficiência de iodo continua sendo uma causa importante de disfunção tireoidiana. O estado de São Paulo é considerado uma região suficiente em iodo. No entanto, as gestantes são consideradas grupo de risco para deficiência iódica devido a maior necessidade de produção dos hormônios tireoidianos ao longo da gestação. Este trabalho objetiva avaliar a suficiência iódica de gestantes residentes em São Paulo e correlacionar as concentrações de iodo com os valores dos hormônios tireoidianos em cada trimestre de gestação. Métodos: Foi realizado estudo transversal com gestantes em pré-natal de baixo risco nos três trimestres de gestação. Foram analisadas 251 mulheres sem doença tireoidiana prévia ou atual, com autoanticorpos antitireoidianos negativos e que não estavam em uso de polivitamínico contendo iodo. A concentração de iodo urinário foi feita em amostra isolada pelo método Sandell- Kolthoff. As dosagens de TSH, T4, T3, T4 livre (T4L), T3 livre (T3L), tireoglobulina (TG), globulina ligadora da tiroxina (TBG) anticorpo antitireoperoxidase (AntiTPO), antitireoglobulina (AntiTG), estradiol e hCG foram feitas por método eletroquimioluminescente. Ultrassonografia da tireoide foi realizada com aparelho Philips IU-22 e transdutor 7,5-12 mHz. Resultados: Os valores de TSH correspondentes aos percentis 2,5 e 97,5 foram 0,38 uIU/mL e 4,23 uIU/mL, respectivamente. Observou-se valores de TSH > 2,5-3,0 uIU/mL em 13,1% gestantes. Valores de TSH > 4 uIU/mL foi observado em 3,6% dos casos. Os valores de T4T e T3T correspondentes aos percentis 2,5 e 97,5 foram 7,8 ug/dL e 16,1 ?g/dL; 122 ng/dL e 249 ng/dL, respectivamente. Os valores de T4l e T3l correspondentes aos percentis 2,5 e 97,5 foram 0,76 ng/dL e 1,42 ng/dL; 0,21 ng/dL e 0,36 ng/dL, respectivamente. Houve aumento significativo na relação T3:T4 ao longo dos trimestres e, em 8% das amostras, essa relação estava acima do valor de referência para gestantes. As dosagens de iodúria não apresentaram diferenças estatísticas entre os três trimestres da gestação. As medianas foram 135ug/L, 153ug/L e 140ug/L, respectivamente. Encontramos iodúria < 150ug/L em 52,2% das gestantes. Comparando o grupo com iodúria < 150ug/L (deficiente em iodo) e o grupo com iodúria entre 150-250ug/L (suficiente em iodo), observou-se diferença significativa nos valores de TSH e de T3 nas gestantes do 2o Trimestre (média de TSH = 2,24 uIU/mL e TSH = 1,78 uIU/mL e média de T3 = 196 ng/dL e T3 = 181 ng/dL entre o grupo deficiente e suficiente, respectivamente). Não houve diferenças significativas entre os valores de TG e o volume tireoidiano ao longo dos trimestres. Conclusão: A frequência de hipotireoidismo subclínico variou de 3,6% a 13,1%, dependendo dos critérios adotados. Não foi possível estabelecer a frequência de hipotiroxinemia materna, devido à ausência de valores de corte de T4l estabelecido na nossa população. Foi encontrada deficiência iódica em 52,2% das gestantes avaliadas. Embora estas gestantes apresentem deficiência leve de iodo, foram necessários mecanismos adaptativos para equilibrar a função tireoidiana materna com possível produção preferencial de T3, aumento da relação T3:T4 e valores mais elevados de TSH. Conclui-se que, embora esta seja uma região suficiente em iodo, as mulheres poderiam se beneficiar com a suplementação deste nutriente durante a gestação / Thyroid dysfunction in pregnancy is associated with increased rate of obstetrical and neonatal adverse outcomes. Iodine deficiency continues to be a major cause of thyroid dysfunction. The state of São Paulo is considered a sufficient iodine region. However, pregnant women are considered a risk group for iodine deficiency due to an increased demand for production of thyroid hormones throughout pregnancy. This study aims to evaluate the iodine sufficiency of pregnant women in São Paulo and to correlate iodine concentrations with thyroid parameters in each trimester of gestation. Methods: A cross-sectional study was carried out with low-risk pregnant women in the three trimesters of gestation. We analyzed 251 women without history of thyroid disease, with negative antithyroid autoantibodies (anti TPO and anti TG) and who were not taking iodine supplementation. The urinary iodine concentration (UIC) was measured by the Sandell-Kolthoff digestion method in casual morning urine samples. Serum TSH, T4, T3, free T4 (FT4), free T3 (FT3), thyroglobulin (TG), TBG, anti-TPO, anti-TG, estradiol and hCG were measured by the electrochemiluminescence method. Thyroid ultrasound was performed with Philips IU-22 and 7.5-12 mHz transducer. RESULTS: The TSH values corresponding to the 2.5 and 97.5 percentiles were 0.38 IU/mL and 4.23 IU/mL, respectively. TSH levels > 2.5-3.0 IU/mL were observed in 13.1% pregnant women. TSH values > 4 IU/mL were observed in 3.6% of the cases. The T4T and T3T values corresponding to the 2.5 and 97.5 percentiles were 7.8 ug/dL and 16.1 ug/dL; 122 ng/dL and 249 ng/dL, respectively. The FT4 and FT3 values corresponding to the 2.5 and 97.5 percentiles were 0.76 ng/dL and 1.42 ng/dL; 0.21 ng/dL and 0.36 ng/dL, respectively. There was a significant increase in the T3:T4 ratio over the trimesters and in 8% of the samples it was above the reference value for pregnant women. The dosages of UIC did not present statistical differences between the three trimesters of gestation. The medians were 135 ug/L, 153 ug/L and 140 ug/L, respectively. We found UIC < 150 ?g/L in 52.2% of pregnant women. Comparing the group with UIC < 150 ?g/L (iodine deficient) and the group with UIC between 150-250 ug/L (sufficient in iodine), a significant difference was observed in TSH and T3 values in the 2nd trimester (TSH = 2.24 IU/mL and TSH = 1.78 IU/mL and mean T3 = 196 ng/dL and T3 = 181 ng/dL between the deficient and sufficient groups, respectively). There were no significant differences between TG values and thyroid volume over the trimesters. Conclusion: The subclinical hypothyroidism frequency ranged from 3.6% to 13.1%, depending on the adopted criteria. It was not possible to establish frequency of maternal hypothyroxinemia, due to the absence of FT4 cutoff established in our population. Iodine deficiency was found in 52.2% of pregnant women evaluated. Although these pregnant women presented mild iodine deficiency, adaptive mechanisms were necessary to balance thyroid function with possible preferential production of T3, increase in T3:T4 ratio and higher values of TSH. It is concluded that although this is an iodine sufficient region, women could benefit from supplementation of this nutrient during pregnancy

<p>Studies were performed to improve iodine deficiency control programs. Goitre rates and cassava processing practices were compared in three Central African Republic (CAR) populations. Short-cuts in cassava processing were associated with elevated urinary thiocyanate and increased goitre rates, suggesting a goitrogenic effect in one population. While improved cassava processing may be beneficial, the priority is to correct the iodine deficiency. </p><p>The use of the urinary iodine/tiocyanate ratio as indicator of goitrogenic effects was explored using data from Tanzania and CAR. As the ratio can be calculated in four mathematically different ways and has physiological shortcomings, its use is discouraged.</p><p>Biannual iodised oil capsule (IOC) distribution in a Tanzanian population of 7 million during nine years was studied. Mean distribution coverage was 64%, mean delay of subsequent distribution 1.25 years, and only 43% of targeted person-time was covered. The cost of capsules constituted more than 90% of total program costs. It is cost-effective to invest more funds in communication, support of peripheral staff and supervision.</p><p>In a highland Tanzanian village, salt iodine content was highly variable compared to national standards. While school-children had adequate urinary iodine, women at delivery and newborns showed signs of in adequate iodine status. Salt iodine concentrations should be monitored during production and distribution down to household level, and iodine status assessed in all vulnerable groups before adjusting recommended salt iodization levels at production.</p><p>WHO's 1994 change in palpation goitre definition considerably lowered specificity and increased measured goitre rates by 25% in Tanzanian school-children compared to the previous system. Ultrasound estimation of thyroid volume under rugged field conditions requires considerable human and material resources yet had a precision only slightly better than palpation. In resource poor settings appropriately trained palpators using the 1960 WHO definition of goitre remain optimal for estimating thyroid size until precision and cost of ultrasound has improved.</p><p>Monitoring of process indicators needs to be an ongoing priority activity, separate from periodic evaluations of impact.</p>

Studies were performed to improve iodine deficiency control programs. Goitre rates and cassava processing practices were compared in three Central African Republic (CAR) populations. Short-cuts in cassava processing were associated with elevated urinary thiocyanate and increased goitre rates, suggesting a goitrogenic effect in one population. While improved cassava processing may be beneficial, the priority is to correct the iodine deficiency. The use of the urinary iodine/tiocyanate ratio as indicator of goitrogenic effects was explored using data from Tanzania and CAR. As the ratio can be calculated in four mathematically different ways and has physiological shortcomings, its use is discouraged. Biannual iodised oil capsule (IOC) distribution in a Tanzanian population of 7 million during nine years was studied. Mean distribution coverage was 64%, mean delay of subsequent distribution 1.25 years, and only 43% of targeted person-time was covered. The cost of capsules constituted more than 90% of total program costs. It is cost-effective to invest more funds in communication, support of peripheral staff and supervision. In a highland Tanzanian village, salt iodine content was highly variable compared to national standards. While school-children had adequate urinary iodine, women at delivery and newborns showed signs of in adequate iodine status. Salt iodine concentrations should be monitored during production and distribution down to household level, and iodine status assessed in all vulnerable groups before adjusting recommended salt iodization levels at production. WHO's 1994 change in palpation goitre definition considerably lowered specificity and increased measured goitre rates by 25% in Tanzanian school-children compared to the previous system. Ultrasound estimation of thyroid volume under rugged field conditions requires considerable human and material resources yet had a precision only slightly better than palpation. In resource poor settings appropriately trained palpators using the 1960 WHO definition of goitre remain optimal for estimating thyroid size until precision and cost of ultrasound has improved. Monitoring of process indicators needs to be an ongoing priority activity, separate from periodic evaluations of impact.

Hypothyroidism is a common endocrine disorder affecting women of reproductive age. On a global level, iodine deficiency is still the most common cause of hypothyroidism. Also genetic variations, in particular SNP rs4704397 in the PDE8B gene, are responsible for a significant proportion of TSH variations.  Untreated hypothyroidism has significant adverse effects on pregnancy and fetal outcome. Most international guidelines suggest targeted thyroid testing in pregnant women with risk factors for thyroid disturbances. In a case-control study, an association between homozygous A/A as well as homozygous G/G carriers of SNP rs 4704397 in PDE8B and recurrent miscarriage was found. The explanation for this association is unknown. In a nationwide survey, all guidelines for thyroid testing and management of hypothyroidism during pregnancy in Sweden were collected and compared with international guidelines. The local guidelines were variable and poorly compliant with the international guidelines. In a follow-up in one district, 5,254 pregnant women were included for subsequent review of their medical reports. We found a targeted thyroid testing rate of 20.1% in clinical practice, with an overall frequency of women with trimester-specific elevated TSH of 18.5%. More disturbingly, half of the women who were on levothyroxine treatment at the time of conception had an elevated TSH level at thyroid testing. In a subsequent cohort study of the 5,254 women, we found the prevalence of trimester-specific elevated TSH and overt hypothyroidism to be equal in targeted thyroid tested and untested women. In a cross-sectional study, a median urinary iodine concentration (UIC) of 98 μg/l was found in the study population. According to WHO/UNICEF/IGN criteria, the population-based median UIC during pregnancy should be 150-249 μg/l. In conclusion, genetic variations may contribute to adverse pregnancy outcomes. In clinical practice, thyroid testing and the management of hypothyroidism during pregnancy is unsatisfactory, regarding the whole chain from development of local guidelines to their implementation and to targeted thyroid testing. Moreover, our results indicate insufficient iodine status in the pregnant population of Sweden.

MSCPNT / Department of Nutrition