Introduction: Oral levothyroxine (LT4) is the standard treatment for hypothyroidism and serum TSH represents the best marker for assessing the proper LT4 dose. The absorption and bioequivalence of different commercial LT4 preparations might be variable. The aim of this study is to compare the efficacy of levothyroxine oral solution vs tablets.
Methods: Fifty-eight patients (six males, 52 females; average age, 46.9±12.0 years) with primary hypothyroidism receiving LT4 therapy were recruited at our center between September 2009 and April 2011. The inclusion criteria were as follows: i) age range between 23 and 75 years; ii) patients with subclinical hypothyroidism (TSH level between 2.5 and 4.5 mU), treated with LT4 oral solution (group O) or tablets (group T), for at least 6 months. The exclusion criteria were as follows: i) pregnancy or lactation; ii) patients with chronic diseases, such as cardiac (coronary disease or arrhythmias), pulmonary, gastrointestinal (malabsorption disorders) and renal disorders or malignancy; iii) use of medications that could potentially interfere with with LT4 absorption.
Results: TSH significantly decreased in both groups (P=0.003), but repeated-measures ANOVA showed no difference between the two groups (P=0.807). A non significant greater decrease was observed at 3 and 6 month in group O vs group T. Average plasma TSH level was negatively correlated with age (P=0.013) and with BMI (P=0.029). TSH decrease was negatively related to basal BMI, while resulted increased in males vs females.
Discussion: Our preliminary observation seems to show a possible greater efficacy of oral solution, as suggested by the non-significant greater decrease of TSH levels. This finding could be related to the slower absorption rate of tablets vs oral solution, as the latter doesnt need dissolution, before absorption starts. However, prolongation of follow-up is needed to confirm our data.