ABSTRACT
Objective To compare the effect of L-T4 taken in the morning vs bedtime on serum thyroid hormone in patients with hypothyroidism.Methods Seventeen patients with primary hypothyroidism were prospectively included.They took L-T4 in the morning for 2 months followed by L-T4 taken during the bedtime for 2 months.Thyroid hormone levels and cholesterol,triglyceride,albumin,creatinine and heart rate were measured.Wilcoxon test and paired t test were used to compare the data.The correlation between the changes of TSH and FT3,FT4 was analyzed respectively by Pearson correlation analysis.Results TSH,FT3,FT4 were:(12.10±7.19) vs (3.90±3.47) mU/L,(4.14±0.86) vs (5.24±1.11) pmol/L,(12.72± 4.40) vs (18.48±2.87) pmoL/L for L-T4 taken in the morning and during the bedtime respectively (t value:6.371,-3.166,-5.435,all P＜0.01).There was no correlation between the changes of TSH and FT3,FT4(r=O.12,0.22,both P＞0.05),respectively.The averaged changes were (8.20±5.31) mU/L,(1.09± 1.42) pmol/L and (5.76±4.37) pmol/L.Triglyceride,cholesterol,albumin,creatinine levels and heart rate were not significantly different with L-T4 taken in the morning and during bedtime (t=0.240,0.017;z=0;t=-0.610,1.588,all P＞0.05).Conclusions L-T4 taken during the bedtime by patients with hypothyroidism would reduce TSH and increase FT3,FT4 levels.This method can maintain the stability of TSH level with no need to increase the dose.