Introduction: Fetal goiter is an infrequent and potentially life-threating condition derived from either fetal hypothyroidism or hyperthyroidism. TSH-receptor stimulating antibodies (TSH-R-ABs) can cross the placenta and induce fetal hyperthyroidism and goiter. We describe a rare case of TSH-R-ABs-induced hyperthyroidism in a woman with autoimmune hypothyroidism (AH) without previous hyperthyroidism.
Case Report: A 28 years old pregnant woman under treatment with Levothyroxine (LT4) for 6 years because of AH was referred during pregnancy. She had history of 2 miscarriages: fetal death at 28th gestational week (GW) two years before and fetal loss in 2015 because of corioamnionitis. Blood tests at 12th GW showed undertreated AH (TSH 31.4 μU/mL, fT4L 0.97 ng/dL) and Levothyroxine dose was increased. At 24th GW, blood tests showed a mild hyperthyroidism (TSH 0.05 μU/mL, fT4 1.53 ng/dL) and LT4 dose was reduced. Fetal ultrasound (US) at 25th GW showed a male fetus with bilateral cerebral ventriculomegaly without other alterations. TORCH serologies were negative, amniocentesis revealed a normal karyotype and fetal MRI showed bilateral cerebral ventriculomegaly and fetal goiter.
To study the fetal thyroid function a blood sample by cordocentesis was obtained and a maternal blood test to examine TSH-R-ABs levels was performed. Meanwhile, fetal US at 26th GW showed tachycardia, mild pericardial effusion, hydrothorax, cardiomegaly, hepatomegaly and splenomegaly. Fetal blood sample showed fetal hyperthyroidism (TSH<0.008, fT4 4.03, fT3 9.92) while maternal TSH-R-ABs were elevated (>40 mUI/mL). Unfortunately, fetal death occurred before knowing the results and antithyroid drugs could not be started. As far as we know, this is the second reported case of TSH-R-ABs-induced fetal thyrotoxicosis in an AH woman.
Conclusion: TSH-R-ABs plasma determination should be mandatory in pregnant women with any previous autoimmune thyroid disease and fetal goiter or thyrotoxicosis. Antithyroid drugs should be started as soon as fetal hyperthyroidism is suspected.
20 - 23 May 2017
European Society of Endocrinology