Breastfeeding 1.5 month old infant (with hyPOthyroidism) on 50mg PTU daily

[Wanderinger]

Hi, I have hyperthyroidism (FT4 normal range, TSH lowered indicating relapse of hyperthyroidism) and am on slight dose of 50mg PTU daily. My baby's last thyroid test came back with slight HYPOthyroidism (free T4 normal range, TSH slightly above range).

I've seen the other posts on this forum but most of the babies are normal while their mothers are on either side of the thyroid problem. In my case if I take PTU will I be aggravating my baby's HYPOthyroidism? He was HYPER at birth with free T4 above range and TSH in normal but 3 weeks after the results reversed (Free T4 in normal and TSH slightly abov erange).

My PD says that his thyroid is transient but I am transferred some of my antibodies to him and its taking time to clear.

Should I be holding off the medication until he is in the ALL clear? Or should I go on to take the medication? My thyroid doctor advises me not to hold off as the hyperthyroid could become full blown.

[admin]

Wanderinger:

This is a problem for your pediatrician and you need to have it taken care of immediately to make sure your infant has sufficient Thyroxine during this critical time of neurodevelopment.

It is unlikely, but possible, that the PTU you are taking is producing this problem. PTU barely passes into milk (about 1.8% of your dose).

So, you have two choices, one is to supplement your infant with small doses of thyroxine and continue to breastfeed, OR, supplement half of your feedings with formula, or stop breastfeeding.

But whatever you do, your infant must have normal thyroid levels at this time in development.



Tom Hale PhD.
InfantRisk Center





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From Medications and Mothers Milk, 2016.

Propylthiouracil (PTU) reduces the production and secretion of thyroxine by the thyroid gland. Only small amounts are secreted into breastmilk. Reports thus far suggest that levels absorbed by infant are too low to produce side effects.[1] In one study of nine patients given 400 mg doses, mean serum and milk levels were 7.7 mg/L and 0.7 mg/L respectively.[2] No changes in infant thyroid have been reported. PTU is the best of antithyroid medications for use in lactating mothers. Monitor infant thyroid function (T4, TSH) carefully during therapy.