Nutritional iodine status & thyroid homeostasis in pregnant women from iodine-deficient environments in india

Asha Chandola; Jayanti Semwal; Snehlata Tendi; Atul Kathait; Graham R. Ball; Nikku Yadav; Srishti Agarwal; Akanksha Uniyal

doi:10.1530/endoabs.92.PS1-10-04

PS1-10-04

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Endocrine Abstracts (2023) 92 PS1-10-04 | DOI: 10.1530/endoabs.92.PS1-10-04

ETA2023 Poster Presentations Basic Thyroid Gland, Iodine & Autoimmunity Basic (9 abstracts)

Nutritional iodine status & thyroid homeostasis in pregnant women from iodine-deficient environments in india

Asha Chandola ¹ , Jayanti Semwal ² , Snehlata Tendi ³ , Atul Kathait ³ , Graham R. Ball ⁴ , Nikku Yadav ⁵ , Srishti Agarwal ² & Akanksha Uniyal ⁵

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Author affiliations

¹Department of Community Medicine, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Uttarakhand, Dehradun, India; ²Department of Community Medicine, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun 248016, India; ³School of Biosciences, Apeejay Stya University, Sohna-Gurgaon, Haryana 122102, India; ⁴Medical Technology Research Centre, Anglia Ruskin University, Chemsford, UK Cm1 1sq, United Kingdom; ⁵Department of Community Medicine, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun 248016, India

Ample literature exists on thyroid functioning and adjustments in Iodine-sufficient pregnant women. But information from endemic-iodine zones is meagre. In this study we attempt to understand how the thyroid copes with the dual challenge of iodine deficiency posed by physiological status of pregnancy and that by Iodine-deficient environment.

Objective: To compare TSH and FT4 profiles and their mutual correlation in iodine-deficient and iodine-sufficient subjects during progressive trimesters of pregnancy.

Methods: Study design: Epidemiological observational survey. Study populations were derived from rural Himalayan foothills in two States Uttarakhand UK, Bihar. BR. Blood & urine samples collected from women 18-45years. UK n =125, longitudinal study. BR n=425 cross sectional. Information on socioeconomic status, maternal thyroid history, dietary-iodine intake, smoking habits and BMI were generated. IEC approval & informed consent were taken. On the first visit, using UIC as biomarker (WHO) pregnant women were categorised into iodine-sufficient (ISS,>150 ug/l) and Iodine-deficient subjects (IDS,<150 ug/l). Table 1 summarises results.

Results: UIC significantly declined in UK longitudinal study despite 77% iodised-salt use. FT4 declined and TSH increased (P < 0.001) in both IDS and ISS, in UK & BR. TSH and FT4 levels were near-normal. ‘r’ was higher in IDS from UK (r=0.51, 0.66, 0.61) as well as BR (0,72, 0,65, 0.636) as compared to that in ISS (UK r=0.17,0.24,0.27 and BR r= 0.07,0.12,0.04) in Trimester I, II, III.

Table 1. Measures of thyroid function and iodine nutrition in Iodine-deficient & iodine-sufficient pregnant women from 8 & 10 villages drawn from Himalayan foothills in States of Uttarakhand & Bihar respectively.
	Tri I (n) Mean +se	Tri II (n) Mean +se	Tri III (n) Mean +se	Tri I Median	Tri II Median	Tri III Median
UK IDS TSH mIU/l	2.34+0.12 (78)	3.11+0.12 (78)	3.90+0.13 (78)	2.18	2.93	3.46
FT4 pm/l	14.69+0.30 (78)	12.74+0.29 (78)	11.09+0.27 (78)	14.41	12.5	10.54
UIC ug/l	(78)	(78)	(78)	138	128	108
UK ISS TSH mIU/l	2.25+0.17 (47)	2.76+0.14 (47)	3.41+0.14 (47)	2.25	2.85	3.44
FT4 pm/l	15.09+0.36 (47)	13.26+0.33 (47)	11.70+0.26 (47)	14.85	13.1	11.85
UIC ug/l	(47)	(47)	(47)	161	133	118
BR IDS TSH mIU/l	2.62+0.12 (68)	3.64+0.10 (147)	4.21+0.09 (160)	2.17	3.32	4.0
FT4 pm/l	14.25+0.3 (68)	12.37+0.2 (147)	11.4+0.2 (160)	14.47	12.4	11.2
UIC ug/l	(68)	(147)	(160)	80	80	84
BIHAR ISS TSH mIU/l	2.99+0.21 (31)	3.83+019 (16)	3.96+0.25 (17)	3.05	3.80	3.70
FT4 pm/l	13.94+0.4 (31)	11.87+0.7 (16)	11.48+0.6 (17)	13.67	11.6	11.0
UIC ug/l	(31)	(16)	(17)	168.5	172	170
NOTE: UK=Uttarakhand longitudinal study, BR= Bihar, cross-sectional study IDS=Iodine-deficient pregnant subjects, ISS=Iodine-sufficient pregnant subjects.

Conclusion: The pituitary-thyroid axis appears to become more sensitive in iodine deficiency resulting in near normal levels of free thyroxine despite consistent UIC decline. Also UIC may not be an ideal biomarker of iodine-deficiency. Intramural grant from SRHU o JS, ACS & AK and UGC JRF to SLT are acknowledged.