A single bolus of high dose levothyroxine (L-T(4)) as a test in cases of suspected poor compliance to L-T4 therapy

BACKGROUND: Though compliance (or adherence) problems, as well as inappropriate levothyroxine (L-T(4)) intake (e.g. with meal, other drugs or certain foods that can significantly affect absorption) are very common, the issue is often either not mentioned or even frankly denied by patients. CASE PRESENTATION: We describe three cases of patients who presented with high TSH (ranging from about 30 to 200 mIU/l), with concomitantly either high, normal or low free thyroxine (FT(4)), despite treatment with high doses of L-T(4). The above mentioned problems with adjustment of L-T(4) dose persisted for several months or even years. Coeliac disease screen was negative in all cases. In all these patients administration of a single bolus of L-T(4) (1000 μg) or two doses of 1000 μg of L-T(4) within 48 h resulted in a quick increase in FT(4) (thus confirming proper absorption) and in normalization of TSH within a week. No adverse effects of administration of these high doses of L-T(4) were observed. CONCLUSIONS: Our data support the efficacy, as well as safety of administration of single bolus of high dose L-T(4) as a test for possible compliance/adherence problems.