Endocrine Abstracts

Background: Combination treatment with Levothyroxine (LT4) and Liothyronine (LT3) in primary hypothyroidism has been debated recently due to restrictions placed by local health boards. National guidance suggests that a short-term trial of combination LT4/LT3 treatment may be considered for individuals who report persistent symptoms despite adequate LT4 replacement.

Method: We created a prescribing protocol for combined LT4/LT3 in clinic using a structured, non-blinded approach, based on national guidance. Prescribing was evaluated in 11 female patients (median age 55y (IQR 48-62); SIMD 4/5 (n=8)) switched from LT4 to combination treatment over a six-months trial. Doses of LT4 and LT3 were adjusted during the treatment period according to TFT, patient-reported symptoms and ThyPro-39 questionnaire.

Results: At baseline median serum TSH was 0.11 (0.04-0.88) mU/l decreasing to 0.06 (0.02-0.49) after 6 months. Proportions of patients with a TSH <0.01mU/l increased from 36.4% to 81.8%, with LT4 doses declining by a mean of 52.3 micrograms, and mean LT3 doses being 16.1 micrograms. At baseline, 54.5% of reported adverse overall quality of life (QOL) declined to 9% of patients after 6 months. Median (IQR) hypothyroid symptoms score at baseline and 6 months were 62.5 (43.8-81.3) and 18.8 (12.5-43.8) respectively. The composite scores which reflected the psychological and social aspect of QOL also improved from a median of 54.5 (IQR 44.3-77.3) to 22.7 (IQR 13.6-40.9).

Conclusion: The local management pathway facilitated combination LT4/LT3 prescription in a systematic manner and improved patient reported outcomes in most patients, but only at doses that put them at risk of potential harm. Achieving a safe level of LT3 replacement was challenging without suppression of TSH below 0.1 mU/l. The local protocol should be supplemented with advice on cardiac and bone health monitoring for patients with persistently low TSH levels (target ideally 0.3-2 mU/l).