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Full term newborn male with a hx of IUGR in utero born to a mother who smoked during pregnancy but who has no hx of thyroid problems, who at birth has some respiratory distress and is noted to have a large neck mass. TSH is 775mcIU/ml and free T4 is 0.39 ng/dl so he was started on 37.5 mcg/day of synthroid then was transferred to another hosp. lat neck film shows ant displacement of the trachea and retropharyngeal fullness. CT of the neck mass showed "large heterogeneous soft tissue mass with septated and lobulated components, likely representing a goiter. enlarged thyroid lobes measure approximately 2.2 x 2 cm in cross-section, and the isthmus in the anterior neck measures 1.4 cm in width.the thyroid gland appears to extend behind the laryngopharyx at the level of the hyoid, displacing the airway anteriorly, and the carotid arteries and the jugular veins are displaced posterolaterally bilaterally. There is distortion of the tracheal cross-section, with a possible reduction in its transverse dimension." T he baby is stable on RA, has no audible stridor, but desats to 60's occasionally with feeds or agitation.
The diagnosis seems most likely to be thyroid dyshormonogenesis questions:
- By treating the hypothyroidism, in what percentage of cases does the goiter shrink in size? and if it does shrink, on what kind of time period would you see shrinkage(weeks, months?)?
- The TSH in 2 days came down to 335. most kids don't get a pertechnetate scan once started on treatment, but to prove that this truly is all thyroid tissue could we still do the scan since the TSH hasn't totally corrected?
- Does anyone else have experience with management of a pt like this?
There is reluctance on part of ent to remove the goiter because the baby is small (2.2 kg) and risk of damage to the recurrent laryngeal nerves would be high. the child's is relatively stable but if the mass doesn't shrink, he may not go home anytime soon given his occasional desats
Thank you.
Dr Joyce Lee, Fellow in endocrinology
University of Michigan
Response
Your infant presents a most interesting and unusual problem as we rarely see goiters of this magnitude in infants these days. In general, the most common etiology would be maternal antithyroid medicine for treatment of maternal Graves', but that does not appear to be the case in your patient. Although the mother smokes and cigarettes contain thiocyanate, I doubt that this is a factor in the absence of iodine deficiency. Nonetheless it would probably be worthwhile to ascertain the mother's dietary habits.I certainly agree that the most likely cause, therefore, is an abnormality of thyroid hormonogenesis. It would be most helpful to do a 123-I uptake and scan (rather than pertechnetate), if that were possible since by following the kinetics of the iodine release (i.e., check uptake early, then at 6 hrs and 24 hrs) you could not only verify that the swelling is thyroid, but determine whether an organification defect is present as well. Also, there is an animal model of congenital hypothyroidism in goats, I believe, that is associated with a large goiter and in which there is an abnormality of thyroglobulin synthesis. Therefore, I would certainly want to check a serum thyroglobulin level in your infant and obtain a urine sample not only for urinary iodine and creatinine but to be used for assessment of an abnormal thyroglobulin molecule as necessary as well. If the neck swelling is thyroid, as it almost certainly is, then I would think that it should shrink relatively rapidly- days and weeks, not months, and surgery is not indicated. However, for the moment if you are concerned about the possibility of respiratory compromise because of its size, then I would push the L-T4 dose by giving an amount that brings the T4 (and free T4) to the high normal range (say 50 mcg. qd) ASAP, and then cut back to 37.5 mcg once this is achieved. I have seen TSH values normalize surprisingly quickly in infants- in a matter of 1 or 2 weeks. I hope that these comments are helpful to you. Please feel free to contact me should you have any further questions or concerns. I would be most interested in learning about the outcome of your patient.
Rosalind Brown MD