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Randomised trial of iodine intake and thyroid status in preterm infants


BACKGROUND Low levels of circulating thyroid hormones have been associated with poorer general and neurodevelopmental outcome in preterm babies and it has been speculated that the association is causal. Low levels of circulating thyroid hormone have been reported after inadequate intake of iodine in preterm infants being fed milk formula.

AIM To investigate whether increased iodine intake from supplemented preterm formula would improve thyroid hormone levels in preterm babies (this study) and hence improve neurodevelopmental status (planned subsequent study).

METHOD A total of 121 preterm infants were entered into a randomised controlled trial of standard (68 μg/l) versus increased (272 μg/l) iodine in preterm formula.

RESULTS The two groups were comparable at recruitment. No evidence of an effect of the intervention on thyroid hormone levels was seen up to 41 weeks after conception.

CONCLUSION Calls for increased iodine content of preterm infant formulas are not justified by this study.

Key message

Key message

  • Increasing milk iodine content in line with the latest recommendations for preterm babies had no effect on thyroid hormone levels in the perinatal period

  • premature
  • randomised controlled trial
  • iodine
  • thyroid function
  • milk formula

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