SLC12A3 and Hypomagnesemia: GS has been described in association with thyroid disorders and should be considered in patients with hyperthyroidism and persistent hypokalemia, especially in those with associated hypomagnesemia and hypocalciuria.<h4>Case summary</h4>In this report, we describe an 18-year-old female who presented with hyperemesis gravidarum and thyrotoxicosis, and was incidentally found to have GS, confirmed by the sequence analysis of <i>SLC12A3.</i> Conclusions.