Introduction: Gestational transient thyrotoxicosis (GTT) affects 23% or pregnancies of European women and 11% of pregnancies of Asian women and typically resolves within the 2nd trimester. GTT rarely manifests with the typical symptoms of thyrotoxicosis and instead is associated with hyperemesis gravidarum. GTT can be confused with thyrotoxicosis occurring in pregnancy which requires prompt treatment with antithyroid drugs (ATDs) to minimise maternal and foetal risk. Injudicious use of ATDs when not required is associated with unnecessary risk to the developing foetus.
Methods: Retrospective cohort study of women attending the antenatal endocrine clinic at Birmingham Heartlands Hospital, UK between 2013 and 2018. Biochemical data and treatment were recorded and clinical outcomes determined by subsequent patient interview post-delivery. Management was compared against British Thyroid Foundation guideline recommendation 3.2 advocating that most women with GTT do not require treatment with ATDs.
Results: Of the 45 patients identified with GTT only 1 was treated with β-blockers and 1 with ATDs. Only 25 patients had normalised TSH (≥0.4 mU/l) by the end of the second trimester. 8 patients did not have a detectable TSH till after delivery. There were no incidences of maternal heart failure, foetal loss or low birth weight. 1 patient developed pre-eclampsia requiring C-section and 1 patient had a premature labour.
Conclusions: The majority of our patients did not require ATDs or β-blockers in accordance with published guidance. Maternal and foetal complications did not occur at rates higher than anticipated in pregnancies not complicated by GTT. A low/ suppressed TSH persisted later than previously reported though time for resolution was not associated with increased risk. Informed discussion and careful observation remain the central management strategy in GTT.