Median Urinary Iodine Concentrations Are Indicative of Adequate Iodine Status among Women of Reproductive Age in Prey Veng, Cambodia

The SELFI Study: Iodine Excess and Thyroid Dysfunction in Women Undergoing Oil-Soluble Contrast Hysterosalpingography

CONTEXT

Hysterosalpingography (HSG) with oil-soluble contrast medium (OSCM) improves pregnancy rates. However, OSCM has high iodine content and long half-life, leading to potential iodine excess.

OBJECTIVE

This work aimed to determine the pattern of iodine excess after OSCM HSG and the effect on thyroid function.

METHODS

A prospective cohort study was conducted of 196 consecutive consenting eligible women without overt hypothyroidism or hyperthyroidism. All completed the study with compliance greater than 95%. Participants underwent OSCM HSG (Auckland, 2019-2021) with serial monitoring of thyrotropin (TSH), free thyroxine (FT4), and urine iodine concentration (UIC) for 24 weeks. The main outcome measure was the development of subclinical hypothyroidism (SCH), defined as a nonpregnant TSH greater than 4 mIU/L with normal FT4 (11-22 pmol/L) in those with normal baseline thyroid function.

RESULTS

Iodine excess (UIC ≥ 300 μg/L) was almost universal (98%) with UIC peaking usually by 4 weeks. There was marked iodine excess, with 90% and 17% of participants having UIC greater than or equal to 1000 μg/L and greater than 10 000 μg/L, respectively. Iodine excess was prolonged with 67% having a UIC greater than or equal to 1000 μg/L for at least 3 months. SCH developed in 38%; the majority (96%) were mild (TSH 4-10 mIU/L) and most developed SCH by week 4 (75%). Three participants met the current treatment guidelines (TSH > 10 mIU/L). Thyroxine treatment of mild SCH tended to improve pregnancy success (P = .063). Hyperthyroidism (TSH < 0.3 mIU/L) occurred in 9 participants (5%).

CONCLUSION

OSCM HSG resulted in marked and prolonged iodine excess. SCH occurred frequently with late-onset hyperthyroidism occasionally. Regular thyroid function tests are required for 6 months following this procedure.

Prevalence of insufficient iodine intake in pregnancy worldwide: a systematic review and meta-analysis

BACKGROUND/OBJECTIVES

Iodine deficiency in pregnant women is related to impaired foetal growth and development. The objective of this study was to estimate the prevalence of insufficient iodine intake in pregnant women from different regions of the world.

SUBJECTS/METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, five electronic databases and Google Scholar grey literature were searched until 10 April 2021. Two reviewers independently conducted article selection, data extraction, and assessment of the risk of bias. Meta-analyses with random effects, subgroup analyses, and meta-regressions were performed.

RESULTS

In total, 4639 observational articles were found, with 61 eligible for inclusion. The population consisted of 163,021 pregnant women adults and adolescents, and the overall prevalence of insufficient iodine intake was 53% (95% confidence interval [CI]: 47-60; I² = 99.8%). Pregnant women who live in insufficient iodine status country had a higher prevalence (86%; 95% CI: 78-93; I² =97.0%) of inadequate iodine nutritional status than to those living in country considered sufficient (51%; 95% IC: 45-57; I² = 99.8%).

CONCLUSION

Despite the progress in iodine fortification policies and periodic monitoring of the iodine nutritional status of the population worldwide, salt iodination alone may not be sufficient to provide adequate iodine status to pregnant women. Thus, other actions may be necessary to improve the nutritional clinical care of pregnant group.

Maternal and neonatal iodine status in Dakshina Kannada district of Karnataka, India

This study was designed to assess iodine status of mother-fetus dyad by estimation of spot urine iodine concentration (UIC) in the study district. It is a cross-sectional study of 250 pregnant women with euthyroid status and their term neonates residing in Dakshina Kannada district. Neonates with foetal growth restriction or requiring intensive care were excluded. Median UIC was quantified using modified Sandell-Kolthoff reaction by microplate method. World Health Organization (WHO) classification was used to categorise the iodine status of pregnant women. Among 250 pregnant women, the majority were primigravida (38%). Median maternal thyroid stimulating hormone (TSH) was 1.54 mIU/l, and median UIC was 352 mcg/l. Urine iodine levels were insufficient (<150 mcg/l) in 1.2% (n = 3), adequate (150-249 mcg/l) in 9.2% (n = 23) and above requirement (250-499 mcg/l) in 89.6% (n = 224); none had excess (> 500 mcg/l). Median birth weight was 3,000 g and head circumference was 34 cm. Median cord blood TSH was 8.1 mIU/l, and median UIC 344.5 mcg/l. All the newborns had adequate (> 100 mcg/l) iodine status, including those born to mothers with insufficient values. Maternal and newborn median UIC showed positive correlation (r = 0.139; p = 0.028). Iodine statuses were above requirement or adequate in pregnant women from the study district and their neonates, respectively, indicating successful salt iodisation.