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Hyperthyroidism hormones transferring through breast milk?

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  • Hyperthyroidism hormones transferring through breast milk?

    I was treated for my hyperthyroidism (Grave's disease) with radioactive iodine last year and a few months later I was pregnant. My levels were monitored throughout pregnancy and only had to take meds (50 mg PTU) the last week of my pregnancy. I stopped the meds after giving birth per my OB. My levels have been checked and are still high. My daughters pediatrician wanted to check her as well and her results came back elevated. She is 4.5 weeks old. He didnt say anything as far as a diagnosis or treatment for her nor did he tell me what the exact numbers were on her labs so I dont know much right now. All he said was that her levels weren't high enough to want to start treating her and that he doesnt think she is specifically hyperthryoid, just that she is being exposed to high hormones from me. I have been exclusively breastfeeding and he wants me to stop breastfeeding altogether but there is a problem... my daughter won't take a bottle. He thinks I may be passing on hormones to her through my breast milk and he wants to also check her levels again in a month. I'm so worried. He said he does not think its neonatal hyperthyroidism because normally after being born the baby will become hypo and she hasn't. He just thinks the exposure to my breast milk is elevating her levels. Anyone know anything about this or have any input? Should I stop breast feeding? What could be causing her elevated levels?

  • #2
    HomieOMI:

    The transfer of levothyroxine into human milk is all but nil. This is well known. Further, it has a long 7 day half-life in an adult, and maybe longer in an infant. Thus the elevated levels may be from maternal exposure during pregnancy.

    I do not think your infants "theoretical hyperthyroidism" is due to thyroid in your milk.

    Tom Hale Ph.d.


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    Levothyroxine is also called T4. Most studies indicate that minimal levels of maternal thyroid are transferred into human milk, and further, that the amount secreted is extremely low and insufficient to protect a hypothyroid infant even while nursing.[1,2,3] The amount secreted after supplementing a breastfeeding mother is highly controversial and numerous reports conflict.

    Anderson[4] indicates that levothyroxine is not detectable in breast milk although others using sophisticated assay methods have shown extremely low levels (4 ng/mL). It is generally recognized that some thyroxine will transfer but the amount will be extremely low. It is important to remember that supplementation with levothyroxine is designed to bring the mother to a euthyroid state, which is equivalent to the normal breastfeeding female. Hence, the risk of using exogenous thyroxine is no different than in a normal euthyroid mother. Liothyronine (T3) appears to transfer into milk in higher concentrations than levothyroxine (T4), but liothyronine is seldom used in clinical medicine due to its short half-life (<1 day).[4]

    1.Mizuta H, Amino N, Ichihara K, Harada T, Nose O, Tanizawa O, Miyai K. Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies. Pediatr Res 1983; 17(6):468-471.
    2.Oberkotter LV. Thyroid function and human breast milk. Am J Dis Child 1983; 137(11):1131.
    3.Sack J, Amado O, Lunenfeld B. Thyroxine concentration in human milk. J Clin Endocrinol Metab 1977; 45(1):171-173.
    4.Anderson PO. Drugs and breast feeding. Semin Perinatol 1979; 3(3):271-278.

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    • #3
      Thank you so much for your reply Dr. Hale. I was hoping it would be you to respond to me so I have a reliable source and info to relay to my daughters pediatrician. So you say her levels may be elevated from when I was still pregnant. Is it possible for these levels to still be elevated this long after giving birth? She will be 5 weeks old tomorrow. Her doctor wants to recheck her labs in a month. What should her labwork look like by then? Should her levels be lower/normal by then?

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      • #4
        HomieOMI:

        Thyroxine in adults has a 7 day half-life. It is probably much longer in an infant.

        I'm betting here levels will drop this time to normal.

        Tom Hale Ph.d.

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        • #5
          I'm really hoping so! I don't want her to have any thyroid problems like I do. I will share this information you have given me with her pediatrician and I hope he will acknowledge it and have no objections to me breast feeding her. At this point I will continue to breast feed her and be hopeful of normal lab results next time. I appreciate your time and will reply with updates or concerns should I have any with her upcoming visits and labwork. One more question, when I do start taking PTU again for treatment, what is a safe level/dosage to stay under in order to safely breast feed?

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          • #6
            Dear HomieOMI:

            The usual adult dose of PTU is 100 mg three times daily. Your dose will be adjusted depending on your blood levels. Only small amounts of PTU are secreted into breastmilk, and side effects to the infant are minimal. To be safe, have your pediatrician monitor your infant's thyroid function (T4, TSH). No changes in infant thyroid have been reported.

            Sincerely,
            Cindy Pride, MSN, CPNP
            TTUHSC InfantRisk Center

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            • #7
              How often should they check my daughters levels?

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              • #8
                Dear HomieOMI,

                That is up to your pediatrician. Further studies would be done according to the results of the first level, and the physical exam evaluation of your infant.

                Sincerely,
                Cindy Pride, MSN, CPNP
                TTUHSC InfantRisk Center

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                • #9
                  nice discussions good.*-*-*-*-*

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                  • #10
                    My daughter had her labs drawn again at 2 months old. Her free T4 is in normal range but her TSH came back low at 0.01. I am worried that she does have hyperthyroidism. Please help!

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                    • #11
                      The range they used for TSH is 0.72-8.0. I read somewhere that babies born early can have a low TSH. She was 3 weeks early but I figured everything would've caught up by now. Also, at her 2 month check up at 9 weeks old, she measured in the 40th percentile for weight and 60th for length. She is still exclusively breastfed.

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                      • #12
                        To add, our pediatrician didnt call this time like how he did after her first draw. I didn't get a copy of her first labs yet so maybe this draw was better than the last and she has made progress so that's why he didnt call? Also, if I remember correctly, TSH takes longer to catch up sometimes right? I vaguely remember my doctor telling me this when I was being drawn regularly to check my function on meds. My T3 & T4 were okay and my TSH was still low. If you need to know her free T4, it was 1.1 on a range of 0.6-1.5.

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                        • #13
                          HomieOMI:

                          If her free T4 is normal, I don't think you have anything to worry about. Talk with your pediatrician.

                          Tom Hale Ph.d.

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