The drug being tested in this study is a new sodium formulation of levothyroxine. Levothyroxine (L-Thyroxine Christiaens®) is used in the treatment of hypothyroidism. This study will investigate the effect of switching subjects taking levothyroxine to a new levothyroxine sodium formulation.~The results of this study will be used to provide instructions to general practitioners and endocrinologists assisting patients on levothyroxine hormone substitution in performing the switch to the new formulation.~The study will enroll approximately 90 patients. Patients receiving the same daily dose of L-Thyroxine Christiaens® during the past 6 weeks and with serum thyroid stimulating hormone (TSH) levels between 0.4-2.5 mU/L will be switched to the equivalent daily dose of the new formulation of levothyroxine. After the switch, patients will be followed up after 2 (± 2 weeks) and 4 months (± 4 weeks).~All participants will be asked to take a daily dose at the same time each day throughout the study.~This study will be conducted in Belgium. Participants will make 3 to 4 visits to the clinic.
The purpose of this study is to investigate the effect of switching participants taking levothyroxine to a new sodium formulation.