Iodine in breastfeeding

I refer to the breastfeeding article¹ by Neil Hotham and Elizabeth Hotham to express my concern about the inclusion of iodine as a drug contraindicated in breastfeeding. In the Table titled ‘Examples of drugs contraindicated in breastfeeding’ it mentions iodine with the comment ‘High doses (>150 micrograms daily) lead to risk of infant hypothyroidism’. I could not find anything in the text or the references of the article that supports this view.

First, iodine is not a drug but an essential element required for normal thyroid function. Therefore including it in a table as an example of drugs contraindicated in breastfeeding is totally unacceptable.

Second, the maternal recommended daily intake for iodine during pregnancy and lactation is 250 micrograms. Given that mild iodine deficiency has been widely prevalent in Australia and continues in women of reproductive age, the National Health and Medical Research Council recommends a daily supplement of 150 micrograms for pregnant and lactating women.² The World Health Organization states that a maternal intake over 500 micrograms per day is excessive but not necessarily harmful.³ It is possible to cause infant hypothyroidism by massive doses of iodine directly to the infant or via mother’s milk over a prolonged period of time.

Finally, I think this article is more likely to cause harm than do good by deterring iodine supplementation during pregnancy and lactation. I would ask that a correction be published.

CJ Eastman
Consultant physician/endocrinologist
Sydney

Neil Hotham and Elizabeth Hotham, the authors of the article, comment:

We agree with Professor Eastman that the main issue of concern is the dose of iodine supplementation. It would have been preferable had the term ‘cautionary use’ been adopted in relation to iodine rather than suggesting an absolute contraindication for doses over 150 micrograms.*

As Professor Eastman notes, the National Health and Medical Research Council recommends that all Australian women who are pregnant or breastfeeding take a daily supplement containing 150 micrograms,⁴ to help achieve the recommended daily intake of 270 micrograms. Hale and Rowe advise limiting doses to not exceed the recommended daily intake,⁵ given the risk of hypothyroidism (even if transient) in the infant.

Lactating women with thyroid disorders should be counselled to seek specialist advice.

* Australian Prescriber has corrected the article by deleting iodine from the list of contraindicated drugs