Levothyroxine Improves Subjective Sleepiness in a Euthyroid Patient with Narcolepsy without Cataplexy

Objective: We discuss the use of levothyroxine for excessive daytime sleepiness (EDS) and prolonged nocturnal sleep time in a euthyroid patient with narcolepsy. Methods: After failure of first-line narcolepsy treatments, a 48-year-old female began levothyroxine (25 mcg/day). After 12 weeks of treatment, the patient was evaluated for improvement in total sleep time and subjective daytime sleepiness assessed by Epworth Sleepiness Scale (ESS). Results: At baseline, ESS score was 16 and total sleep time averaged 16 h/day. After 12 weeks, ESS was 13 and reported total sleep time was 13 h/day. Conclusions: Levothyroxine improved EDS and total sleep time in a euthyroid patient with narcolepsy without cataplexy after 12 weeks without side effects.