Endocrine Abstracts

Background: Monocarboxyate transporter 8 (MCT8) deficiency is a rare neurodevelopmental and metabolic disorder caused by mutations in the thyroid hormone transporter MCT8. The Triac Trial I and subsequent real-world data showed that T3 analogue Triac safely normalizes serum T3 concentrations and ameliorates symptoms of peripheral thyrotoxicosis in paediatric and adult patients.

Objective: To study the effect of Triac on patient-centered outcome measures in the Triac Trial I.

Methods: We performed post-hoc analyses on caregiver-reported patient-centered outcome measures from the multicentre, phase 2, single-arm, open-label Triac Trial I. In this trial, 40 patients with MCT8 deficiency completed 1 year of Triac treatment. At baseline, during clinical visits and at the end of the study, semi-structured interviews were held with caregivers on complex needs and daily care challenges, including motor skills, sleep problems, seizure frequency and most prominent changes. Moreover, parents were asked to report perceived changes in (thyrotoxic) symptoms such as increased perspiration and hyposialia.

Findings: The most prominent changes upon Triac treatment reported by caregivers were improved interaction (22/39), greater alertness (19/39), improved motor skills (12/39), improved head control (7/39), and improved sleep (8/39). For one patient, also negative changes were reported, specifically increased constipation and higher unsettledness. Compared to the baseline visit, excessive perspiration was much less reported (48,6% vs. 8,1%) and less hyposialia (30,6% vs 22,2%) was observed by the caregivers at the end study visit. Seizures and continence were reportedly unchanged. All parents (40/40) preferred to continue Triac treatment.

Interpretation: Treatment with Triac exerts beneficial effects on several patient-centered outcome measures in MCT8 deficiency, corroborating earlier studies that showed positive effects of Triac on clinical and biochemical outcomes in patients with MCT8 deficiency.

Acknowledgements: On behalf of the Triac Trial I study group (names will appear in presentation or poster).