en Endocrinology Endocrinology Original Article Original Article <p><font face="Times New Roman" size="3"> </font><font face="Times New Roman"><b><i><span style="color: blue font-size: 10pt">Background: </span></i></b><span style="font-size: 10pt">Levothyroxine is commonly used in the treatment of patients with hypothyroidism. Levothyroxine is often administered in the morning, on an empty stomach, to increase its absorption. However, many patients have trouble for taking levothyroxine in the morning. The aim of this study was to evaluate the effect of changing administration time of levothyroxine from before breakfast to before dinner on serum levels of TSH and T4.</span></font><font face="Times New Roman" size="3"> </font></p><p><font face="Times New Roman" size="3"> </font><font face="Times New Roman"><b><i><span style="color: blue font-size: 10pt">Methods:</span></i></b><span style="font-size: 10pt"> Fifty hypothyroidism patients aged 18-75 years old were included in the study and randomly divided into two groups. Each group received two tablets per day blindly (<span style="color: black"><font size="2">one levothyroxine tablet </font></span>and one placebo tablet) before breakfast and before dinner. After two months, the administration time for the tablets was changed for each group, and the new schedule was continued for a further two-month period. The serum TSH and T4 levels were measured before and after treatment in each group.</span></font><font face="Times New Roman" size="3"> </font></p><p><font face="Times New Roman" size="3"> </font><font face="Times New Roman"><b><i><span style="color: blue font-size: 10pt">Results:</span></i></b><span style="font-size: 10pt"> Changing the levothyroxine administration time, resulted in 1.47±0.51 µIU/mL increase in TSH level (P=0.001) and 0.35±1.05µg/dL decrease in T4 level (P=0.3).</span></font></p><p><font face="Times New Roman" size="3"> </font><font face="Times New Roman"><b><i><span style="color: blue font-size: 10pt">Conclusion:</span></i></b><span style="font-size: 10pt"> Changing the levothyroxine administration time from before breakfast to before dinner minimally reduced the therapeutic efficacy of levothyroxine.</span><font size="2"><b><i><span style="color: blue"> </span></i></b></font></font><font face="Times New Roman" size="3"> </font></p> Levothyroxine, T4, TSH, administration 134 140 http://caspjim.com/browse.php?a_code=A-10-253-1&slc_lang=en&sid=1 Shahram Ala sh204ala@yahoo.com 10031947532846003520 10031947532846003520 No Department of clinical pharmacy, Faculty of pharmacy, Mazandaran University of Medical Sciences, Sari, Mazandaran province, Iran Ozra Akha zr_akha@yahoo.com 10031947532846003521 10031947532846003521 Yes Diabetes research Center, Mazandaran University of Medical Sciences, Sari, Iran Zahra Kashi kashi_zahra@yahoo.com 10031947532846003522 10031947532846003522 No Diabetes research Center, Mazandaran University of Medical Sciences, Sari, Iran Hosein Asgarirad dr_asgarirad@yahoo.com 10031947532846003523 10031947532846003523 No Department of pharmaceutics, Faculty of pharmacy, Mazandaran University of Medical Sciences, Sari, Mazandaran province, Iran. Adeleh Bahar doctor_bahar2000@yahoo.com 10031947532846003524 10031947532846003524 No Diabetes research Center, Mazandaran University of Medical Sciences, Sari, Iran. Neda Sasanpoor sasanpoornsda@gmail.com 10031947532846003525 10031947532846003525 No Student research committee, Mazandaran University of Medical Sciences, Sari, Mazandaran province, Iran.