Does anyone know if lithium suppresses or destroys thyroxine hormone production? I am curious about this interaction, because reducing lithium (medical advice) for short periods of times, with Synthroid remaining at same dose, hyperactivity, insomnia, and tingling seem to increase. How can we distinguish between hypomania, or mania AND hyperthyroidism? This can happen after very short periods of time (e.g. a month to three) and is similar to manic or hypomanic episodes. Upon restarting regular dose, these symptoms disappear, though discontinuation and restarting requires gradual monitoring.