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Table of Contents
BRIEF COMMUNICATION
Year : 2013  |  Volume : 17  |  Issue : 7  |  Page : 160-161

Subclinical hypothyroidism in the first trimester of pregnancy in North India


Center for Diabetes and Endocrinology, David Anderson Building, Aberdeen Royal Infirmary, Aberdeen, Scotland, United Kingdom

Date of Web Publication11-Oct-2013

Correspondence Address:
Jubbin Jagan Jacob
Clinical Fellow, Center for Diabetes and Endocrinology, David Anderson Building, Aberdeen Royal Infirmary, Aberdeen, AB25 2ZN - Scotland
United Kingdom
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2230-8210.119557

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   Abstract 

Subclinical hypothyroidism based on population and trimester specific cut-offs is reported to complicate 1-2% of all pregnancies. Using the recent Endocrine Society guidelines of 2.5 mIU/L of Thyroid Stimulating Hormone as the upper level of normal in the first trimester the reported prevalence of subclinical hypothyroidism is much higher. Recent publications have also emphasized that there is considerable racial variation in the prevalence of thyroid disorders in pregnancy. Among published literature North Indian women appear to have the highest rates of subclinical hypothyroidism in the first trimester of pregnancy. More widespread use of universal screening and trimester specific ranges in pregnancy for thyroid hormonal assays will lead to a large number of North Indian women requiring treatment for thyroid disorders in pregnancy.

Keywords: First trimester, North India, pregnancy, subclinical hypothyroidism


How to cite this article:
Jacob JJ. Subclinical hypothyroidism in the first trimester of pregnancy in North India. Indian J Endocr Metab 2013;17, Suppl S1:160-1

How to cite this URL:
Jacob JJ. Subclinical hypothyroidism in the first trimester of pregnancy in North India. Indian J Endocr Metab [serial online] 2013 [cited 2019 Jun 17];17, Suppl S1:160-1. Available from: http://www.ijem.in/text.asp?2013/17/7/160/119557

Subclinical hypothyroidism (SCH) is reported to have a prevalence of 1-2% of all pregnancies. [1] However, these older estimates of prevalence have been based on region, assay, and trimester-specific TSH cut-offs for the diagnosis of SCH. Recent Endocrine Society guidelines suggested 0.1 to 2.5 mIU/L as the 'normal' range for TSH values in first trimester. [1] Using the above cut-off for the diagnosis, there have been several studies showing a much larger prevalence of SCH and marked variation between different ethnic groups. The prevalence of any degree of hypothyroidism in pregnancy has varied from 12.3% (Finnish), 15.5% (American) to 35.3% (South American) in these recent studies. [2],[3],[4] In the American study with samples from over half a million pregnant women, there were significant differences in the prevalence of hypothyroid disorders among Asian American women (19.3%) compared to African Americans (6.7%) and Caucasians (16.4%). [3] This was similar to the findings of a small study (unpublished) conducted by us, in which we measured thyroid function tests in the first trimester among 200 pregnant women and found that 16.5% of women had TSH levels > 4 mIU/L and 53.5% had TSH levels ≥ 2 mIU/L. [5] Another small study from Delhi involving 172 normal pregnant women in first trimester (thyroid normalcy suggested by negative thyroid antibodies, clinical assessment, iodine sufficiency, and normal thyroid ultrasound) revealed that the first trimester range of TSH in Indian women to be between 0.6-5.0 mIU/L. [6]

That is why I read with interest the study by Dhanwal and colleagues from Delhi published in the March issue of the journal. [7] Using a TSH cut-off of 4.5 mIU/L, they demonstrated a prevalence of hypothyroidism of 14.3% in the first trimester of pregnancy. The mean first trimester TSH value among the 1000 pregnant women was 3.68 mIU/L and was similar to the previously mentioned study by Marwaha and colleagues from Delhi. [6] In the study by Dhanwal et al., using the Endocrine Society first trimester cut-off for the diagnosis of SCH (>2.5 mIU/L) would have led to over 50% of pregnant women in Delhi being diagnosed with SCH. The Society guidelines suggest that all those diagnosed with SCH in pregnancy should be offered treatment regardless thyroid antibody status, despite no current evidence of benefits because the risks would be negligible. [1]

Preliminary data from the unpublished TULIP study (Thyroid dysfunction in Urban Ludhiana Pregnancies) presented last year at the Endocrine Society Annual meeting also suggests that the prevalence of thyroid dysfunction in North India is very high. The impact on obstetrical and neonatal outcomes in these pregnancies when untreated for SCH is similar to studies from other parts of the world. [8]

Considering these findings, I can make the following observations.

  1. SCH in the first trimester of pregnancy (diagnosed using the Endocrine Society range for TSH) would have a prevalence of over 50% among pregnant women in North India (Delhi and Punjab) if universal screening in pregnancy was the norm. The recent Indian Thyroid Society guidelines have suggested that universal screening should be the norm [9]
  2. The adverse pregnancy and neonatal outcomes among women who have TSH values of > 2.5 mIU/L in the first trimester is similar among North Indian women as in other populations studied despite its 15-fold higher prevalence [8]
  3. In the absence of any data as of yet that treating antibody-negative SCH in pregnancy leads to lesser adverse outcomes, treatment choices would be individual. However, the benefits of offering treatment are likely to outweigh the benefits. The Indian guidelines are unclear about treating women with TSH between 2.5 to the upper normal non-pregnant limits
  4. Once hard outcome data become available that treatment of SCH in pregnancy leads to better outcomes (one large NIH funded clinical trial ongoing, [10] likely results in 2016) and universal screening of pregnant women becomes the standard, there is likely to be tsunami of pregnant women requiring levothyroxine treatment
  5. Another interesting aspect of the whole issue is the question if women in Delhi were being exposed to much higher intakes of dietary iodine compared to women elsewhere (like Kashmir) and this, in turn, was responsible for the high prevalence of SCH in pregnancy. Two papers also published in the same issue of the journal suggest this possibility. The paper by Grewal et al., from the All India Institute in Delhi demonstrates that 72% of pregnant women in the first trimester have more than the required intake of dietary iodine. [11] This is in contrast to the paper by Charoo et al. from Kashmir, in which most pregnant women had normal dietary iodine intake. [12]


In conclusion, preliminary data from studies including the two studies published in the March issue of the journal have highlighted that North Indian women have a high prevalence of thyroid dysfunction in the first trimester of pregnancy. Impact of thyroid dysfunction on pregnancy outcomes appear to manifest with a TSH threshold of > 2.5 mIU/L in the first trimester rather than with a TSH range based on percentiles cut-off derived from apparently 'normal' pregnant women. The large burden of SCH in pregnancy may prove to be a major public health burden in North India once it becomes clear that adverse outcomes can be corrected with screening and early replacement of levothyroxine.

 
   References Top

1.De Groot L, Abalovich M, Alexander EK, Amino N, Barbour L, Cobin RH, et al. Management of thyroid dysfunction during pregnancy and postpartum: An endocrine society clinical practice Guideline. J Clin Endocrinol Metab 2012;97:2543-65.  Back to cited text no. 1
    
2.Altomare M, LA Vignera S, Asero P, Recupero D, Condorelli RA, Scollo P, et al. High prevalence of thyroid dysfunction in pregnant women. J Endocrinol Invest 2013;36:407-11.  Back to cited text no. 2
    
3.Blatt AJ, Nakamoto JM, Kaufman HW. National status of testing for hypothyroidism during pregnancy and postpartum. J Clin Endocrinol Metab 2012;97:777-84.  Back to cited text no. 3
    
4.Mosso ML, Martínez GA, Rojas MP, Margozzini P, Solari S, Lyng T, et al. Frequency of subclinical thyroid problems among women during the first trimester of pregnancy. Rev Med Chil 2012;140:1401-8.  Back to cited text no. 4
    
5.Achit S, Dhar T, Awasthi K, Uppal B, Jacob JJ. Obstetrical and neonatal outcomes in pregnant women with serum thyroid-stimulating hormone (TSH) levels > 2.0 mU/L vs. Those with TSH < 2.0 in the first trimester of pregnancy. Endocr Rev 2011;32:15-24.  Back to cited text no. 5
    
6.Marwaha RK, Chopra S, Gopalakrishnan S, Sharma B, Kanwar RS, Sastry A, et al. Establishment of reference range for thyroid hormones in normal pregnant Indian women. Br J Obstet Gynecol 2008;115:602-6.  Back to cited text no. 6
    
7.Dhanwal DK, Prasad S, Agarwal AK, Dixit V, Banerjee AK. High prevalence of subclinical hypothyroidism during first trimester of pregnancy in North India. Indian J Endocrinol Metab 2013;17:281-4.  Back to cited text no. 7
    
8.Jacob JJ, Aditya K, Achint S, Dhar T, Avasti K. Increased pregnancy losses and poor neonatal outcomes in women with first-trimester TSH levels between 2.5 and 4 mIU/L compared to Euthyroid women with TSH less than or equal to 2.5. Endocr Rev 2012;33:4-1.  Back to cited text no. 8
    
9.Indian Thyroid Society guidelines for management of thyroid dysfunction during pregnancy. Clinical Practice Guidelines, ed. 1. New Delhi: Elsevier; 2012.   Back to cited text no. 9
    
10.Spong CY. Thyroid therapy for mild thyroid deficiency in pregnancy. ClinicalTrials.gov Available from: http://clinicaltrials.gov/. [Last accessed on 2013 Jul 26].  Back to cited text no. 10
    
11.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;17:289-93.  Back to cited text no. 11
    
12.Charoo BA, Sofi RA, Nisar S, Shah PA, Taing S, Jeelani H, et al. Universal salt iodization is successful in Kashmiri population as iodine deficiency no longer exists in pregnant mothers and their neonates: Data from a tertiary care hospital in North India. Indian J Endocrinol Metab 2013;17:310-7.  Back to cited text no. 12
    



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