Determinants of Levothyroxine Treatment in Patients with Hypothyroidism

BACKGROUND/AIMS: Hypothyroidism is a common disorder. Thyroid dysfunction and treatment failure can cause major health problems. Levothyroxine is the only treatment available for hypothyroidism. Its effectiveness depends on several factors. In this article, we aimed to determine which factors can cause hypothyroidism and how they affect its treatment.MATERIALS AND METHODS: One hundred and eighty subjects with hypothyroidism who were referred to an endocrinology outpatient clinic were enrolled in this study. The patients were grouped according to treatment effectiveness. These groups were compared in terms of age, gender, medication adherence, thyroid autoantibodies [anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (TG)], and thyroid heterogeneity. Co -ingested medications were investigated, and treatment effectiveness was compared.RESULTS: The mean age was 46.8 +/- 12.8 years. One hundred and nine out of 162 patients were female (67.2%). Treatment failure was 55.6% (90/162). Patients with inadequate adherence to their levothyroxine treatment had higher anti-TPO and anti-TG levels (p=0.01). Ninety-three out of 162 patients (57.4%) had a medium/high adherence to levothyroxine therapy. Patients with low adherence (42.6%) experienced a higher treatment failure rate (p=0.01). Treatment failure rates did not vary according to gender or thyroid sonographic heterogeneity (p=0.49; p=0.66). Thirty-four out of 162 patients (21%) used medications which altered thyroid function. Additional medication use had an insignificant effect on thyroid-stimulating hormone levels (p=0.32).CONCLUSION: These findings demonstrate high treatment failure rates, and that levothyroxine treatment adherence is an important subjective factor to determine treatment efficacy. Clinicians and patients should focus on underlying factors in order to increase treatment success.