Endocrine Abstracts

Ropeginterferon alfa-2b is a mono-pegylated type I interferon (P-I) used in myeloproliferative neoplasm (MPN). Thyroid dysfunction (TD) is a well recognised side-effect of P-I (1). We conducted a review determining TD prevalence and current practice on thyroid function (TF)/antibody (TAB) monitoring during P-I treatment. Retrospective data was collected, from electronic and physical medical records from July 2019-March 2024, on 37 adult MPN patients in the South-West of Ireland. Exclusion criteria; TD, thyroid hormone replacement, radioactive-iodine or thyroid surgery prior to P-I therapy. TAB were detected using an Alllinaseed assay (Abbott Laboratories). Normal thyroid-stimulating-hormone (TSH) defined as 0.35-4.0 mIU/l, normal T4 9-19 pmol/l. Negative results defined as: thyroglobulin antibody < 115 IU/mL; thyroid peroxidase antibody < 34 IU/mL; and thyrotropin receptor antibody  < 1.75 IU/mL. The average pre-treatment TSH was 1.81mIU/l and T4 was 12.98mIU/l, although 21 patients (59%) did not have a baseline T4 analysed. Baseline TAB were checked in only 2 patients (5%). The average 2 year TSH was 6.9mIU/l and T4 was 11.11mIU/l, only 12 patients (33%) had T4 checked at regular intervals. 5 patients (14%) developed overt hypothyroidism. 3 of which (8%) were anti-TPO positive, TAB not analysed in remainder. Time to positivity was assumed to be 4 years. The average TF monitoring frequency was once per 5.53 months. 12 patients (32%) were monitored 3 monthly in accordance with guidelines. All hypothyroid patients were managed with Eltroxin 50 mg adequately and remain hypothyroid on P-I. The findings are consistent with the current body of literature surrounding P-I—induced TD. TF monitoring is not in accordance with standard guidelines for P-I treated patients. Local guidelines have been curated to guide the monitoring and management of TD in these patients. i.e. TSH, free T3 and TAB prior to treatment and 3 monthly TSH and free T4.