Is Liothyronine safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Liothyronine. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
Relevant published information was not found as of the revision date. However, the thyroid hormone content of human milk from the mothers of very preterm infants appears not to be sufficient to affect the infant s thyroid status.[ 10 ]
Effects on milk supply
Adequate thyroid hormone serum levels are required for normal lactation. Replacing deficient thyroid levels should improve milk production caused by hypothyroidism. Supraphysiologic doses of liothyronine would not be expected to further improve lactation.
Levels in milk
Milk levels of liothyronine have not been measured after exogenous administration of T3 in humans. Although somewhat controversial, liothyronine, unlike levothyroxine (T4), might pass into milk in amounts that affect infant thyroid status.[ 3 - 7 ] In a study of a new analytic technique, concentrations of several thyroid hormones were measured in 30 milk samples. The mean levothyroxine (T4) concentration was 94 mcg/L (range 48 to 194 mcg/L) and the mean dextrothyroxine concentration was 135 mcg/L (range 115 to 158 mcg/L). The mean liothyronine (T3) concentration was 52 mcg/L (range 32 to 109 mcg/L) and the mean reverse T3 concentration was 65 mcg/L (range 21 to 180 mcg/L). Among the 30 samples, the dextrothyroxine concentration was always higher than the levothyroxine concentration, and the reverse T3 concentration was always higher than the liothyronine concentration. The levels of levothyroxine were also higher than liothyronine levels. Several other thyroid hormones such as thyroxine; monoiodothyronine; 3,3 and 3,5-diiodothyronine were also measured.[ 8 ] Maternal Levels. In a study of 56 mothers with thyroid disorders, 50 had hypothyroidism and were being treated with levothyroxine; 5 mothers had controlled hyperthyroidism with no medications and 1 had hyperthyroidism treated with a medication. Milk levels of thyroid hormones were free T4 4.5 ng/L, total T4 29.6 mcg/L, free T3 2.3 ng/L and total T3 0.35 mcg/L. The average milk to serum level ratios over the period were free T4 0.32, total T4 0.3, free T3 0.78 and total T3 0.26. Levels of free and total T3 and total T4 in milk were positively correlated with their respective plasma levels.[ 9 ] Infant Levels. Relevant published information was not found as of the revision date.
Alternatives LactMed lists
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.