Endocrine Abstracts

Introduction: Despite adequate treatment with LT₄ monotherapy, many patients with primary hypothyroidism still report complaints, as this treatment can not exactly imitate the endogenous homeostasis. We examined whether the different domains of HR-QOL were affected by the existence of a thyroid disorder and use of LT₄ substitution, and whether a lower ratio of free triiodothyronine (fT₃⁾–free thyroxine (fT₄⁾ could predict lower HR-QOL.

Methods: A total of 16 631 participants from the population-based LifeLines Cohort Study, of Western European descent and with normal TSH values (0.4–4.5 mU/l), were evaluated; 368 of them used LT₄ monotherapy. TSH, fT₄ and fT₃) were measured with electrochemiluminescent immunoassay on the Roche Modular E170 Analyzer. HR-QOL was assessed using the Short Form-36 questionnaire.

Results: Mean (±S.D.) age was 51±13 years and BMI 26.9±4.7 kg/m² in the LT₄ users, vs 43±13 years and 25.5±3.8 kg/m² in the non-users; 90% of LT₄ users were females. We observed considerably higher fT₄ and lower fT₃ levels in LT₄ users, with the fT₃/fT₄-ratio being 25% lower in LT₄ users, despite similar TSH levels in both groups. 50% of LT₄ users had a fT₃/fT₄-ratio which was below the 2.5th percentile of euthyroid individuals. LT₄ users reported poorer HR-QOL, the largest reduction was observed in physical functioning, bodily pain, general health and vitality. In the non-users, those in the lowest tertile of the fT₃/fT₄-ratio reported a significantly lower HR-QOL in the domains physical functioning, bodily pain, and general health compared to participants in the middle and highest tertile.

Conclusion: Patients treated with LT₄ monotherapy for primary hypothyroidism report low HR-QOL. In subjects not using LT₄, a lower fT₃/fT₄-ratio was associated with more impairments in HR-QOL.

Disclosure: This work was supported by NCHA, Netherlands Consortium for Healthy Ageing, Bio-SHaRE-EU, Biobank Standardisation and Harmonisation for research excellence in the European Union. Bioresource research impact factor BRIF4568.