Hyperthyroidism associated with hyperemesis gravidarum

Hyperemesis gravidarum is an uncommon presentation of hyperthyroidism in pregnancy which is usually attributable to autoimmune (Graves') disease. While this condition necessitates treatment with antithyroid drugs, a syndrome of transient hyperthyroidism associated with hyperemesis gravidarum that resolves spontaneously is also recognised. Differentiation between these two conditions may prove problematic in practice. We report two cases of hyperthyroidism associated with severe hyperemesis gravidarum. Intractable hyperemesis continued in one patient despite normalisation of circulating free thyroid hormone concentrations with carbimazole. Neither patient exhibited clinical or immunological features of autoimmune thyroid disease, suggesting in retrospect that they had the syndrome of transient hyperthyroxinaemia associated with hyperemesis gravidarum rather than Graves' disease. The role of antithyroid drugs in the treatment of self-limiting transient hyperthyroidism associated with hyperemesis gravidarum requires clarification.