Endocrine Abstracts

Introduction: Low adherence to levothyroxine replacement therapy can be up to 27% in some population. Suboptimal levothyroxine replacement in the community is primarily due to medication non-adherence. The Levothyroxine Absorption Test (LAT) is a well-described intervention at confirming medication non-adherence or malabsorption. We audited the short-term and long-term clinical outcomes of patients undergoing LAT at our Centre since 2016.

Methods: LAT: Patients receive a weekly observed oral levothyroxine dose calculated at 1.6 mg x weight x 7 or adjusted based on clinician’s clinical judgment for a total of 4 weeks. Thyroid function tests (TFTs) are measured hourly for 6 hours after the first dose and then weekly thereafter.

Results: 16 patients underwent LAT: 12 patients with persistently raised TSH on levothyroxine replacement (Suboptimal Replacement Group) and four patients who were agreeable to transition off Liothyronine therapy (Transition Group). Suboptimal Replacement Group: Mean referral TSH was 58 mIU/l (range 20.6 to >100). Weekly Levothyroxine dose varied from 700 to 3500 mg. No patient had evidence of malabsorption on day 1 serial TFTs measurements. All patients demonstrated a decrement in TSH levels on weekly TSH monitoring. 9/12 (75%) were discharged back to GP care after LAT. For 10 patients with available follow-up TSH results, euthyroidism (TSH <10 mIU/l) was maintained in 80%, after a mean duration of 2.8 years (range 1-6) since LAT. Transition Group: Three patients were transitioned off Liothyronine therapy and one patient was established on a significantly reduced dose of Liothyronine in combination with Levothyroxine therapy.

Conclusion: The Levothyroxine Absorption Test offers a successful non-confrontational long-term therapeutic option for the majority of patients with persistently low adherence to daily Levothyroxine replacement therapy for Primary Hypothyroidism. For patients agreeable to transitioning off Liothyronine therapy, LAT offers a useful adjunct at achieving an individualised patient-centred clinical outcome.