Endocrine Abstracts

Introduction: Hypothyroidism can present in a variety of ways, from unexpected abnormal blood results in seemingly asymptomatic patients to those with a multitude of debilitating symptoms. Levothyroxine dose titration is a challenge often faced by physicians. We identified 8 difficult cases which following MDT discussion underwent the Thyroxine Absorption Test (TAT) to gain further clarification (Walker et al. 2013).

Aim: To identify if the issue is absorption, patient compliance with medication or true thyroid hormone resistance.

Method: Notes and results of 8 patients with various underlying aetiologies of hypothyroidism (table 1) were retrospectively reviewed over 20 months. All patients were female, age ranging from 27-63 years (mean and median 41.6 and 55.5 years respectively). BMI range of 33-41 kg/m2 (mean 36.8 kg/m2). At the first consultation, 6 patients were on levothyroxine and 2 were on combination levothyroxine and triliothyronine. Triliothyronine was stopped 2 weeks prior to the TAT. As per TAT protocol, thyroxine dose was calculated at 1.6 mg/kg/day x 7 which equated to a range of 1000-1200 mg weekly (mean of 1075 mg). Blood tests were subsequently carried out over 6 hours and 4, 6 and 24 weeks with levothyroxine dose adjusted accordingly.

Conclusion: Patient compliance, rather than absorption, was identified as the main challenge. Thyroid hormone resistance was not identified in this cohort. All patients had a reference range FT4 at some point, either during the TAT or following a period of supervised weekly dosing. General improvements in wellbeing was reported but sample size was insufficient for statistical analysis. Psychological support could potentially benefit this group of patients to improve insight into their condition and thus further impact their wellbeing.

References: Walker et al. (2013) ‘A thyroxine absorption test followed by weekly thyroxine administration: a method to assess non-adherence to treatment’, European Journal of Endocrinology, 168 pp.913-917.