Figure 1.

Individual serum levels of serum free thyroxine (FT4), with indicated normal reference range and (dotted line) midnormal range value. Except for two patients, serum FT4 had been measured in different laboratories for the other five patients. However, each patient used always the same laboratory, which used the same kit throughout follow-up. Empty circles (○) refer to the pretreatment period. Black circles (●) refer to the treatment period with stable doses of tablet l-T4. Black squares (■) and black triangles (▲) refer to the postswitch period, when patients were under the same daily dose of l-thyroxine but using a novel formulation (liquid or softgel capsule, respectively).