Sammendrag
Background/Aim: Iodine is an essential component of thyroid hormones required for the normal growth, development and functioning of the body. Its deficiency causes intellectual impairment, reproductive risks such as overt hypothyroidism, infertility, gestational hypertension, increased first trimester abortions and still births. Paradoxically, iodine deficiency disorders (IDD) are among the easiest and cheapest preventable disorders. This study therefore evaluated dietary iodine status and some thyroid parameters in first trimester (10th–12th week) pregnant women
Methods: Forty-two healthy pregnant women, mean age and gestational age of 30±5.22 years and 11.43±0.83 weeks respectively were recruited in consecutive manner for this study after obtaining their informed consents. Urinary iodine levels were analysed in casual urine samples using the ammonium persulphate method as described by Dunn et al while thyroid stimulating hormone (TSH) and free thyroxine (fT4 ) were measured in serum using Enzyme Immunoassay technique.
Results: 40.5% of the participants had adequate dietary iodine, 47.6% had more than adequate, 9.5% had mild iodine deficiency, while 2.4% had excess dietary iodine. 92.9% of the participants had normal TSH values, 4.8% and 2.4% fell in the hypothyroid and hyperthyroid ranges respectively. 91.4% of the participants had normal values for fT4 , 8.6% had below normal while none had above. Qualitative salt analysis shows iodization of salt in all the salt samples tested.
Conclusion: This study reveals adequate iodine nutrition in the first trimester sub-population, however, screening for overt and subclinical hypothyroidism should still be strongly considered.
Keywords: Iodine, iodine deficiency disorders, thyroid hormones, first trimester pregnant women
Résumé
Contexte / But: L’iode est un composant essentiel des hormones thyroïdiennes nécessaires à la croissance, au développement et au fonctionnement normaux du corps. Sa carence entraîne une déficience intellectuelle, des risques de reproduction tels que l’hypothyroïdie manifeste, l’infertilité, l’hypertension gestationnelle, l’augmentation des avortements au premier trimestre et des d’enfants mort-nés. Paradoxalement, les troubles dus à la carence en iode (IDD) sont parmi les troubles évitables les plus faciles et moins chers. Cette étude a donc évalué l’état de l’iode alimentaire et certains paramètres thyroïdiens chez les femmes enceintes du premier trimestre (10eme - 12eme semaine).
Méthodes: Quarante-deux femmes enceintes en bonne santé, âge moyen et âge gestationnel de 30 ± 5,22 ans et 11,43 ± 0,83 semaines respectivement ont été recrutés de façon consécutive pour cette étude après avoir obtenu leur consentement informé. Les niveaux d’iode urinaire analysés dans des échantillons d’urine occasionnels en utilisant la méthode du persulfate d’ammonium décrite par Dunn et al tandis que la thyréostimuline (TSH) et la thyroxine libre (fT4 ) ont été mesurées dans le sérum en utilisant la technique d’essai d’immune enzymatique.
Résultats: 40,5% des participants avaient un apport alimentaire adéquat en iode, 47,6% avaient plus qu’adéquat, 9,5 % avaient une légère carence en iode et 2,4% avaient un excès d’iode alimentaire. 92,9% des participants avaient des valeurs de TSH normales, 4,8% et 2,4% étaient à portée avec l’hypothyroïdie et l’hyperthyroïdie respectivement. 91,4% des participants avaient des valeurs normales pour l’fT4 , 8,6% avaient un taux inférieur à la normale alors qu’aucun n’avait au-delà. L’analyse qualitative des sels a montrée l’iodation du sel dans tous les échantillons de sel testés.
Conclusion: Cette étude révèle une nutrition adéquate en iode dans la sous-population du premier trimestre; cependant, le dépistage de l’hypothyroïdie manifeste et sub-clinique devrait être fortement envisagé.
Mots clés: Iode, troubles de la carence en iode, hormones thyroïdiennes, femmes enceintes au premier trimester
Correspondence: Dr. Olubayo M. Akinosun, Department of Chemical Pathology, College of Medicine, University of Ibadan, Ibadan, Nigeria. E-mail: bayoakin2002@yahoo.com
Referanser
de Escobar GM, Obregon MJ and Escobar del Rey F. Role of thyroid hormone during early brain development. Eur J Endocrinol 2004; 151: U25–U37.
Santiago-Fernandez P, Torres-Barahona R, Muela-Martinez JA, et al.Intelligence quotient and iodine intake: a cross-sectional study in children. J Clin Endocrinol Metab 2004; 89: 3851–3857.
Qian M, Wang D, Watkins WE, et al. The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China. Asia Pacific J Clin Nutr 2005; 14: 32–42.
Sanchez-Vega J, del Rey FE, Farinas-Seijas H and de Escobar GM. Inadequate iodine nutrition of pregnant women from Extremadura (Spain). Eur J Endocrinol2008; 159: 439–445. (doi:10.1530/EJE-08-0309)
Das V, Kamra S, Mishra A, Agarwal A and Agarwal CG. Screening for gestational diabetes and maternal and fetal outcome. J Obstet Gynecol Ind 2004; 54(5): 449–451.
Glinoer D. Maternal and foetal impact of chronic iodine deficiency. Clin Obstet Gynecol 1997a; 40: 102–116.
Glinoer D. The regulation of thyroid function during normal pregnancy: importance of the iodine nutrition status. Best Pract Res Clin Endocrinol Metab2004; 18: 133–152.
Glinoer D. The thyroid in pregnancy: a European perspective. Thyroid Today 1995; 18: 1–11.
Glinoer D. The regulation of thyroid function in pregnancy: pathways of endocrine adaptation from physiology to pathology. Endocr Rev 1997b; 18: 404–433.
Glinoer D. The systematic screening and management of hypothyroidism and hyperthyroidism during pregnancy. Trends in Endocrinol Metab 1998; 9: 403–411.
Burrow GN, Fisher DA and Larsen PR. Maternal and foetal thyroid function. N Engl J Med 1994; 331(16): 1072–1078.
Zimmermann M and Delange F.Iodine supplementation of pregnant women in Europe: a review and recommendations. Eur J Clin Nutr 2004; 58: 979–984.
Stilwell G, Reynolds PJ, Parameswaran V, et al. The influence of gestational stage on urinary iodine excretion in pregnancy. J Clin Endocrinol Metab 2008; 93: 1737–1742. (doi:10.1210/jc.2007-1715).
Davison JM and Dunlop W. Renal hemodynamics and tubular function normal human pregnancy. Kidney Int1980; 18(2):152–161.
American Thyroid Association (ATA), Public Health Committee – Becker DV, Braverman LE, Delange F, Dunn JT, Franklyn JA, Hollowell JG, Lamm SH, Mitchell ML, Pearce E, Robbins J, Rovet JF. Iodine supplementation for pregnancy and lactation-United States and Canada: Recommendations of the American Thyroid Association. Thyroid 2006; 16: 949–951.
Hetzel B. The story of iodine deficiency. An international challenge in nutrition. Oxford: Oxford University Press1989.
Semiz S, Senol U, Bircan O, et al. Thyroid hormone profile in children with goitre in an endemic goitre area. J Paediatr Endocrinol 2001; 14(2): 171–176.
Springer D, Zima T and Limanova Z. Reference intervals in evaluation of maternal thyroid function during the first trimester of pregnancy. Eur J Endocrinol 2009; 160(5): 791–797.
Glinoer D, de Nayer P, Bourdoux P, et al. Regulation of maternal thyroid during pregnancy. J Clin Endocrinol Metab 1990; 71: 276–287.
Stricker R, Echenard M, Eberhart R, et al. Evaluation of maternal thyroid function during pregnancy: the importance of using gestational age-specific reference intervals. Eur J Endocrinol 2007; 157(4): 509–514.
Marwaha RK, Chopra S, Gopalakrishnan S, et al. Establishment of reference range for thyroid hormones in normal pregnant Indian women. BJOG 2008; 115(5): 602–606.
Lee RH, Spencer CA, Mestman JH, et al. Free T4 immunoassays are flawed during pregnancy. Am J Obstet Gynecol 2009; 200(3): 260–266.
Fister P, Gaberscek S, Zaletel K, et al. Thyroid function in the third trimester of pregnancy and after delivery in an area of adequate iodine intake. Int J Gynaecol Obstet 2010; 112(1): 52–55.
Berghout A and Wiersinga W.Thyroid size and thyroid function during pregnancy: an analysis. Eur J Endocrinol 1998; 138: 536–542.
Ojule AC and Osotimehin BO. The influence of iodine deficiency on the cognitive performance of school children in Saki, South-west Nigeria. Afr J Med Med Sci 1998a; 27(1-2): 95–99.
Ojule AC and Osotimehin BO. Maternal and neonatal thyroid status in Saki, Nigeria. Afr J Med Med Sci 1998b; 27(1-2): 57–61.
Akanji AO, Mainasara AS and Akinlade KS. Urinary iodine excretion in mothers and their breast-fed children in relation to other childhood nutritional parameters. Eur J Clin Nutr1996; 50:187–191.
Pop VJ, van Baar AL and Vulsma T. Should all pregnant women be screened for hypothyroidism? Lancet 1999; 354: 1224–1225.
Dunn TJ, Crutchfield HE, Gutekunst R and Dun AD. Methods for measuring iodine in urine, in International Council for Control of Iodine Deficiency Disorders (ICCIDD). Wageningen 1993; pp 1–71.
World Health Organization (WHO). Assessment of iodine deficiency disorders and monitoring their elimination. A guide for program managers 2001;pp 1–122.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, Eds. Burtis CA, Ashwood ER, Bruns DE. Fourth edition, Saunders, an imprint of Elsevier Inc. 11830 Westline Industrial Drive St. Louis, Missouri 63146. Printed in the Rakmo Press (P) Ltd C-59 Okhla Industrial Area Phase-1, New Delhi – 110020, India pp 2298.
Connolly R. An increase in thyrotoxicosis in southern Tasmania after an increase in dietary iodine. Med J Aust 1971; 1: 1268–1271.
Todd C, Allain T, Gomo Z, et al. Increase in thyrotoxicosis associated with iodine supplements in Zimbabwe. Lancet 1995; 346: 1563–1564.
Bourdoux P, Ermans AM, Mukalay WA, et al. Iodine-induced thyrotoxicosis in Kivu, Zaire. Lancet 1996; 347: 552–553.
Hollowell JG, Staehling NW, Hannon WH, et al. Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994). J Clin Endocrinol Metab 1998; 83(10): 3401–3408.
Caldwell KL, Miller GA, Wang RY, Jain RB and Jones RL. Iodine status of the U.S. population, National Health and Nutrition Examination Survey 2003–2004. Thyroid 2008; 18:1207–1214.
Caldwell KL, Makhmudov A, Ely E, Jones RL and Wang RY. Iodine status of the U.S. population, National Health and Nutrition Examination Survey, 2005–2006 and 2007–2008. Thyroid 2011; 21: 419–427.
Pekonen F, Alfthan H, Stenman UH and Ylikorkala O. Human chorionic gonadotropin (hCG) and thyroid function in early human pregnancy: circadian variation and evidence for intrinsic thyrotropic activity of hCG. J Clin Endocrinol Metab 1988; 66: 853–856.
Persani L. Hypothalamic thyrotropin-releasing hormone and thyrotropin biological activity. Thyroid 1998; 8: 941–946.
Chin WW, Carr FE, Burnside J and Darling DS. Thyroid hormone regulation of thyrotropin gene expression. Recent Prog Horm Res 1993; 48: 393–414.