Endocrine Abstracts

Background: Levothyroxine (LT4) is one of the most prescribed drugs worldwide. Once started, about 90% of patients continue LT4 treatment long-term.

Aim of the study: To evaluate the necessity of long-term thyroxine supplementation and to determine the prognostic factors that could identify which patients may discontinue LT4 treatment.

Design and methods: LT4 replacement therapy was paused for at least six weeks in all patients consecutively visiting our department, excluding those who have a definite need for L-thyroxine use (replacement after total thyroidectomy), those on thyroid-altering medication, women wishing to conceive and those who gave birth last year. 231 individuals were assessed (84% females), aged 48 years (SD=16.5), who were categorized into the following categories: a) unknown reason for thyroxine supplementation (n=62), b) presence of thyroid nodules (n=90), normal TSH before thyroxine administration (n=44), over 10 years’ use (n=10), therapy initiated post-pregnancy (n=20). Thyroid function was evaluated before and after the thyroxine pause. A value of TSH ≥4.5 IU/ml post treatment discontinuation was considered as ‘relapse’ and LT4 was reinstituted in those individuals. The potential prognostic factors analyzed were family history of thyroid dysfunction, sex, age, dose per BMI and dose per kg, thyroid volume, thyroid ultrasound characteristics, positivity of thyroid autoantibodies, basal TSH values and reason for the initial treatment indication.

Results: 25.54% (83% females) of the studied subjects relapsed. Of the above-described factors, only diffuse inhomogeneous echogenicity was tentatively identified as the only predictive factor for relapse (71% vs 57%, P:001). The age (47.27±15.45 vs 48.17±16.98 years, P:0.72), the positivity of TPOAb (69%% vs 54%, P:0.064) and basal TSH values (1.51±0.96 ΩΣ. 1.57±0.84, P:0,81) did not differ significantly among the two groups.

Conclusions: One out of four individuals evaluated required thyroxine treatment. The need for a patient-centered approach regarding L-thyroxine supplementation and for a thorough review of patient history was evident.