ORIGINAL ARTICLE

Iodine Deficiency to Iodine Excess: Have We Come Full Circle?
İyot Eksikliğinden İyot Fazlalığına; Çemberi Tamamladık mı?
Received Date : 28 Oct 2020
Accepted Date : 17 Feb 2021
Available Online : 17 Mar 2021
Doi: 10.25179/tjem.2020-79791 - Makale Dili: EN
Turk J Endocrinol Metab. 2021;25:158-165
Bu makale, CC BY-NC-SA altında lisanslanmış açık erişim bir makaledir.
ABSTRACT
Objective: Recent studies have demonstrated an increase in the prevalence of hypothyroidism among pregnant women. Since hypothyroidism during pregnancy may increase fetomaternal morbidity, it is imperative to study the reason underlying this condition. Therefore, the present study was aimed to assess the iodine status in pregnant women and its correlation with hypothyroidism. Material and Methods: The present study was designed as a cross-sectional study to detect thyroid dysfunction in pregnant women in a tertiary-care hospital setting. Detailed demographics and the medical and obstetric history of the included subjects were recorded, and their baseline serum thyrotropin (TSH) and urinary iodine levels were determined. The women diagnosed with hypothyroidism were subjected to reflex testing for thyroid peroxidase antibodies (TPOAb). Results: The Median Urinary Iodine concentration of the study population, determined using the spot urinary iodine concentration of 545 women, was 255μg/L, which was higher than the level recommended in the WHO Guidelines. Among the 33% women (n=180) detected to be hypothyroid (TSH level >2.5mIU/L in the 1st trimester or >3.0mIU/L in the 2nd or 3rd trimester), 32% women (n=67) were positive for TPOAb. The correlation between the TSH levels and the urinary iodine levels was not significant (p=0.688); a significant correlation was observed between the urinary iodine levels and positivity for TPOAb (p=0.047). Conclusion: The current iodine status among pregnant North Indian women indicates a trend toward Iodine excess, with a significant association with the high prevalence of thyroid autoimmunity in the study population.
ÖZET
Amaç: Son çalışmalar, gebelerdeki hipotiroidizm prevalansında bir artış olduğunu göstermiştir. Gebelikte hipotiroidizm fetomaternal morbiditeyi artırabileceğinden, bu durumun altında yatan nedeni araştırmak şarttır. Bu nedenle, bu çalışmada gebelerde iyot durumu ve hipotiroidizm ile ilişkisinin değerlendirilmesi amaçlanmıştır. Gereç ve Yöntemler: Bu çalışma, 3. basamak hastane ortamında gebelerdeki tiroid disfonksiyonunu saptamaya yönelik kesitsel bir çalışma olarak tasarlanmıştır. Çalışmaya alınanların ayrıntılı demografik özellikleri ve tıbbi ve obstetrik geçmişleri kaydedilmiş ve başlangıç serum tirotropin (TSH) seviyeleri ve idrar iyot seviyeleri belirlenmiştir. Hipotiroidizm teşhisi konan kadınlara, tiroid peroksidaz antikorları (TPOAb) için refleks testi uygulanmıştır. Bulgular: Çalışma popülasyonundaki 545 kadının, spot idrar iyot konsantrasyonu kullanılarak, belirlenen Medyan İdrar İyot konsantrasyonu 255μg/L idi ve bu Dünya Sağlık Örgütü Kılavuzları’nda önerilen seviyeden daha yüksekti. Hipotiroid (TSH seviyesi 1. trimesterde >2,5 mIU/L ya da 2. veya 3. trimesterde >3,0 mIU/L) olduğu tespit edilen 180 kadından (%33) 67’sinde (%32) TPOAb pozitifti. TSH seviyeleri ile idrar iyot seviyeleri arasındaki korelasyon anlamlı değildi (p=0,688); TPOAb pozitifliği ile idrar iyot seviyeleri arasında ise anlamlı bir korelasyon gözlendi (p=0,047). Sonuç: Kuzey Hindistanlı gebe kadınlar arasındaki mevcut iyot durumu, çalışma popülasyonundaki yüksek tiroid otoimmünite prevalansı ile anlamlı bir ilişki gösteren iyot fazlalığına doğru bir eğilim olduğunu göstermektedir.
KAYNAKLAR
  1. Urinary iodine concentrations for determining iodine status deficiency in populations. Vitamin and Mineral Nutrition Information System. Geneva: World Health Organization; 2013:
  2. Katagiri R, Yuan X, Kobayashi S, Sasaki S. Effect of excess iodine intake on thyroid diseases in different populations: A systematic review and meta-analyses including observational studies. PLoS One. 2017;12:e0173722. [Crossref]  [PubMed]  [PMC] 
  3. Goel P, Kaur J, Saha PK, Tandon R, Devi L. Prevalence, Associated Risk Factors and Effects of Hypothyroidism in Pregnancy: A Study from North India. Gynecol Obstet Invest. 2012;74:89-94. [Crossref] 
  4. Alexander EK, Pearce EN, Brent GA, Brown RS, Chen H, Dosiou C, Grobman WA, Laurberg P, Lazarus JH, Mandel SJ, Peeters RP, Sullivan S. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. 2017;27:315-389. Erratum in: Thyroid. 2017;27:1212. [Crossref]  [PubMed] 
  5. Stagnaro-Green A, Abalovich M, Alexander E, Azizi F, Mestman J, Negro R, Nixon A, Pearce EN, Soldin OP, Sullivan S, Wiersinga W; American Thyroid Association Taskforce on Thyroid Disease During Pregnancy and Postpartum. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011;21:1081-1125. [Crossref]  [PubMed]  [PMC] 
  6. Benhadi N, Wiersinga WM, Reitsma JB, Vrijkotte TG, Bonsel GJ. Higher maternal TSH levels in pregnancy are associated with increased risk for miscarriage, fetal or neonatal death. Eur J Endocrinol. 2009;160:985-991. [Crossref]  [PubMed] 
  7. Sahu MT, Das V, Mittal S, Agarwal A, Sahu M. Overt and subclinical thyroid dysfunction among Indian pregnant women and its effect on maternal and fetal outcome. Arch Gynecol Obstet. 2010;281:215-220. [Crossref]  [PubMed] 
  8. Liu H, Shan Z, Li C, Mao J, Xie X, Wang W, Fan C, Wang H, Zhang H, Han C, Wang X, Liu X, Fan Y, Bao S, Teng W. Maternal subclinical hypothyroidism, thyroid autoimmunity, and the risk of miscarriage: a prospective cohort study. Thyroid. 2014;24:1642-1649. [Crossref]  [PubMed]  [PMC] 
  9. Lata K, Dutta P, Sridhar S, Rohilla M, Srinivasan A, Prashad GR, Shah VN, Bhansali A. Thyroid autoimmunity and obstetric outcomes in women with recurrent miscarriage: a case-control study. Endocr Connect. 2013;2:118-124. [Crossref]  [PubMed]  [PMC] 
  10. Ghassabian A, Bongers-Schokking JJ, de Rijke YB, van Mil N, Jaddoe VW, de Muinck Keizer-Schrama SM, Hooijkaas H, Hofman A, Visser W, Roman GC, Visser TJ, Verhulst FC, Tiemeier H. Maternal thyroid autoimmunity during pregnancy and the risk of attention deficit/hyperactivity problems in children: the Generation R Study. Thyroid. 2012;22:178-186. [Crossref]  [PubMed]  [PMC] 
  11. Dhanwal DK, Bajaj S, Rajput R, Subramaniam KA, Chowdhury S, Bhandari R, Dharmalingam M, Sahay R, Ganie A, Kotwal N, Shriram U. Prevalence of hypothyroidism in pregnancy: An epidemiological study from 11 cities in 9 states of India. Indian J Endocrinol Metab. 2016;20:387-390. [Crossref]  [PubMed]  [PMC] 
  12. Gayathri R, Lavanya S, Raghavan K. Subclinical hypothyroidism and autoimmune thyroiditis in pregnancy-a study in south Indian subjects. J Assoc Physicians India. 2009;57:691-693. [PubMed] 
  13. Luo Y, Kawashima A, Ishido Y, Yoshihara A, Oda K, Hiroi N, Ito T, Ishii N, Suzuki K. Iodine excess as an environmental risk factor for autoimmune thyroid disease. Int J Mol Sci. 2014;15:12895-12912. [Crossref]  [PubMed]  [PMC] 
  14. Liu J, Mao C, Dong L, Kang P, Ding C, Zheng T, Wang X, Xiao Y. Excessive Iodine Promotes Pyroptosis of Thyroid Follicular Epithelial Cells in Hashimoto's Thyroiditis Through the ROS-NF-κB-NLRP3 Pathway. Front Endocrinol (Lausanne). 2019;10:778. [Crossref]  [PubMed]  [PMC] 
  15. Dineva M, Fishpool H, Rayman MP, Mendis J, Bath SC. Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women. Am J Clin Nutr. 2020;112:389-412. [Crossref]  [PubMed] 
  16. Shan Z, Chen L, Lian X, Liu C, Shi B, Shi L, Tong N, Wang S, Weng J, Zhao J, Teng X, Yu X, Lai Y, Wang W, Li C, Mao J, Li Y, Fan C, Teng W. Iodine Status and Prevalence of Thyroid Disorders After Introduction of Mandatory Universal Salt Iodization for 16 Years in China: A Cross-Sectional Study in 10 Cities. Thyroid. 2016;26:1125-1130. [Crossref]  [PubMed] 
  17. Alsayed A, Gad AM, Abdel-Baset H, Abdel-Fattah A, Ahmed A, Azab A. Excess urinary iodine is associated with autoimmune subclinical hypothyroidism among Egyptian women. Endocr J. 2008;55:601-605. [Crossref]  [PubMed] 
  18. Bastemir M, Emral R, Erdogan G, Gullu S. High prevalence of thyroid dysfunction and autoimmune thyroiditis in adolescents after elimination of iodine deficiency in the Eastern Black Sea Region of Turkey. Thyroid. 2006;16:1265-1271. Retraction in: Thyroid. 2007;17:189. [Crossref]  [PubMed] 
  19. Laurberg P, Cerqueira C, Ovesen L, Rasmussen LB, Perrild H, Andersen S, Pedersen IB, Carlé A. Iodine intake as a determinant of thyroid disorders in populations. Best Pract Res Clin Endocrinol Metab. 2010;24:13-27. [Crossref]  [PubMed] 
  20. Teng X, Shan Z, Chen Y, Lai Y, Yu J, Shan L, Bai X, Li Y, Li N, Li Z, Wang S, Xing Q, Xue H, Zhu L, Hou X, Fan C, Teng W. More than adequate iodine intake may increase subclinical hypothyroidism and autoimmune thyroiditis: a cross-sectional study based on two Chinese communities with different iodine intake levels. Eur J Endocrinol. 2011;164:943-950. [Crossref]  [PubMed] 
  21. Grewal E, Khadgawat R, Gupta N, Desai A, Tandon N. Assessment of iodine nutrition in pregnant north Indian subjects in three trimesters. Indian J Endocrinol Metab. 2013;17:289-293. Erratum in: Indian J Endocrinol Metab. 2013;17:508. Desai, Ankush [added]; Tandon, Nikhil [added]. [Crossref]  [PubMed]  [PMC] 
  22. Vega-Vega O, Fonseca-Correa JI, Mendoza-De la Garza A, Rincón-Pedrero R, Espinosa-Cuevas A, Baeza-Arias Y, Dary O, Herrero-Bervera B, Nieves-Anaya I, Correa-Rotter R. Contemporary Dietary Intake: Too Much Sodium, Not Enough Potassium, yet Sufficient Iodine: The SALMEX Cohort Results. Nutrients. 2018;10:816. [Crossref] 
  23. Asvini K Subasinghe, Simin Arabshahi, Doreen Busingye, Roger G Evans, Karen Z Walker, Michaela A Riddell, Amanda G Thrift. Association between salt and hypertension in rural and urban populations of low to middle income countries: a systematic review and meta-analysis of population based studies. Asia Pac J Clin Nutr. 2016;25:402-413.
  24. Johnson C, Santos JA, Sparks E, Raj TS, Mohan S, Garg V, Rogers K, Maulik PK, Prabhakaran D, Neal B, Webster J. Sources of Dietary Salt in North and South India Estimated from 24 Hour Dietary Recall. Nutrients. 2019;11:318. [Crossref]  [PubMed]  [PMC] 
  25. Rana R, Raghuvanshi RS. Effect of different cooking methods on iodine losses. J Food Sci Technol. 2013;50:1212-1216. [Crossref]  [PubMed]  [PMC] 
  26. National family health Survey (NFHS-4) 2015-16. f PP.328. Accessed July 30th, 2020. [Link]