This cohort study investigated the potential associations between thyroid function, iodine nutrition and timing of iodine supplement initiation in mildly-to-moderately iodine-deficient pregnant and postpartum women. 137 pregnant women were enrolled and followed up at gestational weeks (GWs) 18 and 36, 3- and 6-month postpartum. In brief,
- The median urinary iodine concentration (UIC) was below the recommended WHO concentrations throughout pregnancy and until 6-month postpartum, indicating mild-to-moderate deficiency
- Urinary iodine concentration: creatinine ratio (UIC: Cr) was negatively associated with concentrations of free triiodothyronine (fT3) and free thyroxine (fT4)
- Thyroid-stimulating hormone (TSH) was positively associated with iodine intake, while fT3 and fT4 were negatively associated with iodine intake.
- Neither beneficial nor harmful effect on thyroid hormone function was found if the iodine-containing supplement had been initiated after conception
- Initiating an iodine-containing supplement prior to conception and continuing through pregnancy was associated with lower TSH concentrations but higher concentrations of fT4 and fT3, which may suggest improved thyroid function.
- To conclude, optimization of iodine intake should start before pregnancy
Link to the full report:
Næss S et al. Iodine nutrition and iodine supplement initiation in association with thyroid function in mildly-to-moderately iodine-deficient pregnant and postpartum women. J Nutr. 2021;151(10):3187-3196.
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