Abstract

Studies justify prescribing levothyroxine (LT4) as the first-line treatment for patients with hypothyroidism. However, the strict administration requirements, since LT4 optimally absorbed during fasting state which mandates delaying of any food for at least 30 minutes. Consequently, the compliance with these instructions may be problematic for the patient's adherence. Therefore, we aimed to systematically assess the effects of bedtime LT4 administration on the degree of hypothyroidism clinical parameters. Several databases were systematically searched for relevant papers on alternative Levothyroxine administrating time. The papers published in the English language from the first available article up to March 2020 were approached. The terms hypothyroidism, LT4, and bed-time were used. Out of 316 papers retrieved, only seven fulfilled the inclusion and exclusion criteria. In the current review, seven full texts fulfilled the inclusion and exclusion criteria, of the two, showed a reduction in thyroid stimulating hormone (TSH) when thyroxine was administered at bedtime. Three studies showed that the bed-time administration is as effective as standard morning time administration. The last two studies examine the possibility of LT4 co-administration with meals and both show statistically significant higher TSH seen with non-fasting regimens. The review concluded that the medication adherence will be affected by the patient's preference. Therefore, if Levothyroxine administrating (30-60 minutes) before breakfast is not convenient, alternative regiment, such as bed-time or co-administration with the meal, may also be an option.

Key words: Bedtime, hypothyroidism, levothyroxine, review.