Gestational transient thyrotoxicosis refers to non-autoimmune hyperthyroidism in pregnant women and it is associated with hyperemesis gravidarum. During pregnancy, there are some alterations in thyroid gland, such as elevation of thyroxine binding globulin, increased iodium clearance in kidneys, and stimulation of thyroid gland by human chorionic gonadotropin. Hitherto, the pathophysiology underlying the development of gestational transient thyrotoxicosis has not been fully recognized. Studies showed that human chorionic gonadotropin, an agonist of thyroid stimulating hormone, may stimulate thyroid stimulating hormone receptor, leading to increased thyroid hormone. Diagnosis of gestational transient thyrotoxicosis is established based on inexistence history of previous hyperthyroidism, elevation of thyroid hormone, absence of hyperthyroid abnormalities signs on physical examination (such as: enlargement of thyroid gland, exophthalmia), and the absent of positive thyroid autoantibody. Generally, gestational transient thyrotoxicosis does not require medication, unless if hyperemesis gravidarum is present, thus the patient has to be hospitalized to receive intravenous rehydration, electrolyte correction and antiemetic medication. On cases with worsened or prolonged symptoms, anti-thyroid agents such as short term propiltiourasil is needed.