Follow-up of newborns of mothers with Graves' disease.

BACKGROUND

Overt neonatal Graves' disease is rare, but may be severe, even life threatening, with deleterious effects on neural development. The main objective of this study was to describe the course of thyrotropin (TSH) and free thyroxin (fT4) levels, as well as postnatal weight gain in relation to fT4 levels, in neonates born to women with Graves' disease without overt neonatal thyrotoxicosis. Such information is important to deduce the optimal schedule for evaluation.

METHODS

We conducted a retrospective chart review of neonates born to mothers with Graves' disease between January 2007 and December 2012. The records were reviewed for sex, gestational age, birth weight, maternal treatment during pregnancy, and maternal thyroid stimulating immunoglobulin (TSI) level. For each visit in the clinic, the data included growth parameters, presence of symptoms suspected for hyperthyroidism, blood test results (levels of TSH, fT4, and TSI), and treatment.

RESULTS

Ninety-six neonates were included in the study (49 males), with a total of 320 measurements of thyroid function tests (TSH and fT4). Four neonates (4%) had overt neonatal Graves' disease; one of them along with nine others were born preterm. In 77 (92.9%) of the remaining 83 neonates (the subclinical group), fT4 levels were above the 95th percentile on day 5. All had normal fT4 on day 15. A negative association was found between fT4 and weight gain during the first two weeks.

CONCLUSIONS

In this cohort, most neonates born to mothers with Graves' disease had a subclinical course with abnormal fT4 levels that peaked at day 5. After day 14, all measurements of fT4 returned to the normal range, although measurements of TSH remained suppressed for up to three months. Elevated fT4 was associated with poor weight gain.