The effects of atorvastatin on the serum concentrations of thyroid stimulating hormone and free thyroxine in hypothyroid patients treated with levothyroxine

Mohammad Abbasinazari. Shahid Beheshti University of Medical sciences, Clinical pharmacy, Iran

Introduction: Because of efficacy and tolerability, statins are well known pharmacological class for the treatment of hypercholesterolemia in human1,. Atorvastatin prescribe extensively for the treatment of hyperlipidemia2. Hyperlipidemia is a common problem of hypothyroid patients. There are few clinical case reports regarding drug interaction between levothyroxine and lovastatin3 and simvastatin4, indicating decreased levothyroxine effects. This study aimed at determining possible interaction between atorvastatin and levothyroxine in hypothyroid patients by assessing serum levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4), the 2 significant paraclinical indices for levothyroxine therapy5.

Methods: In a cross sectional study, 30 eligible hypothyroid patients receiving levothyroxine (50-150 μg/d) were selected. All patients signed their informed written consent. Blood samples were obtained before and after 3 months of simultaneous treatment with atorvastatin (20 mg/d) and levothyroxine to evaluate the serum concentration of TSH and FT4.

Results: There was no significant difference between the serum concentration of TSH (P=0.65) or FT4 (P=0.45) before and after 3 months of simultaneous treatment. Also, there was no aggravation or initiation of any sign or symptom of hypothyroidism in the patients during the study period.

Discussion: Findings of the present study suggest that there may not be any important drug interaction between atorvastatin and levothyroxine.

Conclusion: The findings of the present study indicate that there was no significant change in the evaluated laboratory parameters. Therefore, they suggest that most likely there is no interaction between atorvastatin and levothyroxine. We believe that the findings provide an additional benchmark for further studies involving more patients.

1. Weng TC, Yang YH, Lin SJ, Tai SH. A systematic review and meta-analysis on the therapeutic equivalence of statins. J Clin Pharm Ther 2010; 35: 139-51.

2. Chatzizisis YS, Koskinas KC, Misirly G et al. .Risk Factors and Drug Interactions Predisposing to Statin-Induced Myopathy. Drug Saf 2010;33:171-187

3. Demke DM, Gormley GJ, Tobert JA. Drug interaction between thyroxine and lovastatin. N Eng J Med 1989; 321: 1341-2.

4. Kisch E, Segall HS. Interaction between simvastatin and L-thyroxine. Ann Intern Med 2005; 143: 547.

5. Koda-kimble MA, Young Lloyd lee. Thyroid disorders. In: Dong BJ.Applied therapeutics: the clinical use of drugs. 9th ed. Baltimore: Williams and Wilkins, 2009.p. 6-7.