Subclinical Hypothyroidism Prevalence in Pregnant Ladies in AL-Hilla city in Iraq Ban

Recent guidelines adapted unique pregnancy thyroid function screening tests because pregnancy subclinical hypothyroidism is associated with different adverse outcomes. There are no data from Iraq about the prevalence of thyroid hypo function in 1 trimester of pregnancy. This study aims to find the prevalence of thyroid dysfunction in 1 trimester. Patients and Methods: In this descriptive cross sectional study, thyroid stimulating hormone (TSH) was measured in 100 pregnant women from May 2017-December 2017 in Babylon teaching hospital for maternity and pediatric and in private clinic. If TSH was more than 2.5 mIU/L in the first trimester, free T4 was measured to diagnose then differentiate between subclinical & overt hypothyroidism. If free T4 was in the normal value (0.71.8 ng/dl) the diagnosis was subclinical hypothyroidism and if below the normal value, overt hypothyroidism was diagnosed. Results A total of 100 pregnant women were evaluated. Twenty-eight of them were diagnosed as hypothyroidism. Subclinical hypothyroidism and overt hypothyroidism were present in 24 (24%) and 4 (4%) women respectively. Most of the subclinical and overt hypothyroidism cases were diagnosed in the first trimester. 1Introduction There are different studies which show decreased intellectual and motor development of babies is associated with abnormalities of their mothers thyroid function [1, 2]. Thyroid gland disorders are one of the common endocrine problems in pregnant ladies. It is now well known that not only overt, but also subclinical hypothyroidism (SCH) has adverse side effects on maternal and fetal outcome [1]. Fetal thyroid gland is not working up to 12 weeks of gestation. Thyroid releasing hormone crosses the placenta to stimulate fetal thyroid gland. So maternal thyroid function is very important during the first trimester [4]. During the first trimester, human chorionic gonadotropin (hCG) level is elevated that act similar to thyroid stimulating hormone (TSH) (α subunit of hCG and TSH is similar). So the effect of TSH, under the influence of placental hCG, is low during pregnancy with the decreased TSH level in the first trimester beings poorly defined and an upper level of 2.5 mIU/L. At 10-12 weeks of gestation, plasma level of hCG begins to decline to act like TSH, so TSH is increased a little to an upper normal level of 3mIU/L in the second and third trimester[4]. However, a study in Iraq stated that TSH level did not show significant differences in different trimesters of pregnancy. There is no data from Iraq about the prevalence of SCH in pregnancy and there is debate about unique screening of thyroid function tests in pregnancy. We, therefore, studied the thyroid function of pregnant ladies to know the prevalence of subclinical cases of hypothyroidism. 2Patients and Methods: This descriptive cross-sectional study was done on 100 pregnant ladies in Babylon teaching hospital for maternity and pediatrics in Alilla city and in private clinic , Babylon university of Medical Sciences . For all pregnant ladies from May 2017-December 2017 during routine laboratory workup, screening of thyroid function tests was done by TSH level in the endocrine laboratory by the chemiluminescent immunoassay (Elecsys 2010, Hitachi, Diamond, Japan). If TSH level was >2.5 mIU/L in the first trimester or TSH >3 mIU/L in the second or Journal of University of Babylon for Pure and Applied Sciences (JUBAS) by University of Babylon is licened under a Creative Commons Attribution 4.0 International License. 2018.


1-Introduction
There are different studies which show decreased intellectual and motor development of babies is associated with abnormalities of their mothers thyroid function [1,2].Thyroid gland disorders are one of the common endocrine problems in pregnant ladies.It is now well known that not only overt, but also subclinical hypothyroidism (SCH) has adverse side effects on maternal and fetal outcome [1].Fetal thyroid gland is not working up to 12 weeks of gestation.Thyroid releasing hormone crosses the placenta to stimulate fetal thyroid gland.So maternal thyroid function is very important during the first trimester [4].During the first trimester, human chorionic gonadotropin (hCG) level is elevated that act similar to thyroid stimulating hormone (TSH) (α subunit of hCG and TSH is similar).So the effect of TSH, under the influence of placental hCG, is low during pregnancy with the decreased TSH level in the first trimester beings poorly defined and an upper level of 2.5 mIU/L.At 10-12 weeks of gestation, plasma level of hCG begins to decline to act like TSH, so TSH is increased a little to an upper normal level of 3mIU/L in the second and third trimester [4].However, a study in Iraq stated that TSH level did not show significant differences in different trimesters of pregnancy.There is no data from Iraq about the prevalence of SCH in pregnancy and there is debate about unique screening of thyroid function tests in pregnancy.We, therefore, studied the thyroid function of pregnant ladies to know the prevalence of subclinical cases of hypothyroidism.

2-Patients and Methods:
This descriptive cross-sectional study was done on 100 pregnant ladies in Babylon teaching hospital for maternity and pediatrics in Alilla city and in private clinic , Babylon university of Medical Sciences .For all pregnant ladies from May 2017-December 2017 during routine laboratory workup, screening of thyroid function tests was done by TSH level in the endocrine laboratory by the chemiluminescent immunoassay (Elecsys 2010, Hitachi, Diamond, Japan).If TSH level was >2.5 mIU/L in the first trimester or TSH >3 mIU/L in the second or third trimester, free T4 measurement was done by chemiluminescent immunoassay to know whether it is subclinical or overt hypothyroidism.If serum FT4 was in the normal range (0.8-1.7 ng/dl) SCH was diagnosed and if below the normal range, overt hypothyroidism was the diagnosis.Their demographic (maternal age, gestational age, parity ,BMI, residence) and clinical details were collected as part of routine antenatal care and were recorded.We asked the women about personal and family history of thyroid disease.Duration of gestation was calculated from last menstrual period and verified by ultrasonography.Informed consent was taken from all participants.SPSS software version 20 was used for data analysis.

3-Results
Table1shows that the mean age of pregnant women who participated in the study is 26.32±6.04years.Regarding body mass index and weeks of gestation, the mean is 29.12±3.46kg/m2and 8.0±2.06weeksrespectively.Over half of pregnant women (60.0%) reside in urban areas while (40.0%) reside in rural areas .Up to 64.0% 0f pregnant women are multigravida.Figure 1 shows that subclinical hypothyroidism represents 24.0% of the total pregnant mothers in the first trimester who participated in the study while 4.0% have overt hypothyroidism.Table 3 shows that fisher exact test was conducted to show the association between parity, residence with the diagnosis of hypothyroidism.There is a significant association between residence and diagnosis (p-value <0.001)

4-Discussion
We found the prevalence of subclinical hypothyroidism to be 6.15%.According to the study by Casey et al. the prevalence of subclinical hypothyroidism during early pregnancy is common, affecting about 5.5% pregnant women [7,8].A similar result was reported by Allan et al. [9], Vaidya et al. [10] and Mannisto et al. [11].These studies are in contrast with the report by Gillett who stated that routine screening of pregnant women is not necessary for thyroid function, unless they were at increased risk of thyroid disease [12].This suggests that subclinical hypothyroidism is more common in pregnant women especially in Iraqi pregnant ladies.Subclinical hypothyroidism during early pregnancy has been shown to be associated with the impaired neuropsychological development of children and several other adverse outcomes, including preterm delivery, preeclampsia and increased fetal mortality [1,4,8,10,11,[13][14][15][16].But the study by Cleary Goldman et al. showed that subclinical hypothyroidism is detectable in 2.2% in the first and second trimesters with no adverse outcome in pregnant women with thyroid hypofunction [15].Pregnancy has much influence on the thyroid gland and thyroid function.Physiological changes of pregnancy cause the thyroid gland to increase production of thyroid hormones to meet maternal and fetal needs.TSH and human chorionic gonadotropin (hCG) have identical α subunits whereas the β subunits differ in their amino acid sequence [4].There is also an uncertainty regarding the most appropriate initial screening test for thyroid dysfunction in pregnancy.The consensus guidelines recommend using TSH level as the initial test [10,14,16].The American College of Obstetricians and Gynecologists (2007) concluded that although observational data were consistent with the possibility that subclinical hypothyroidism was associated with adverse neuropsychological development, there have been no interventional trials to demonstrate improvement in decision to do routine thyroid screening of pregnant women.There are reports that testing the high-risk group only for thyroid function would miss about one third of pregnant women with overt/subclinical hypothyroidism [7,9,[17][18][19][20][21][22].Most of our patients with overt hypothyroidism were diagnosed in the first trimester.This is in agreement with a previous study by Sahu et al. in India in which the rate of overt hypothyroidism was reported as 4.6% [3].We know that patients with overt hypothyroidism usually are infertile and if they become pregnant, complications of pregnancy such as abortion may occur.So universal screening for thyroid function appears logical.Also, diagnosis of subclinical hypothyroidism during the third trimester is necessary to treat them and prevent postpartum depression.

5-Conclusion
There is a high percentage of pregnant women that reach second and third trimester of pregnancy with undiagnosed thyroid disease.It is , therefore, necessary to screen women with a serum TSH, if they are pregnant or deciding to become pregnant to overcome the complications that may occur due to maternal hypothyroidism.

CONFLICT OF INTERESTS
There are no conflicts of interest.

Figure 1 :
Figure 1: Distribution of pregnant mothers according to the diagnosis of hypothyroidism.

Figure
Figure3depicts that there was a significant mean difference of TSH according to age,(p-value =0.006).Regarding FT4 also there was a significant mean difference according to age ,(p value =0.03)

Figure 3 :
Figure 3: Distribution of TSH and FT4 according to the age of the pregnant mothers.

Figure 4
Figure 4 depicts the higher percentage of subclinical cases of hypothyroidism was present in women aged 20-35 years (83.3%),whilethose aged younger than 20 years ,the percentage was 16.7%

Figure 4 :
Figure 4: Association between age of the pregnant women and diagnosis.

Table 4 : Mean difference of age , BMI and GA according to diagnosis of hypothyroidism in pregnant women.
*P-value≤ 0.05 was significant.