The hormone replacement drug levothyroxine is the most common therapy for people with reduced function of the thyroid gland. The optimal dosage varies considerably between individuals, and reaching the correct dosage is often a time-consuming task. To reduce the time needed for dose adjustments, we have developed a model for calculating each patient’s optimal dosage and an associated decision support tool (DST). We present the study protocol for a randomised controlled trial using the DST in initiation and adjustment of levothyroxine therapy for thyroidectomised patients. The aim of the study is to assess the tool’s efficacy on therapeutic target achievement and to investigate whether faster dose adjustments lead to better patient-reported outcomes on symptoms and health-related quality of life (HRQoL).

We will conduct a randomised, controlled, multicentre, non-blinded, parallel arm trial with three intervention groups and one control group. We will include 240 patients undergoing total or completion thyroidectomy in three Norwegian hospitals. Patients allocated to the three intervention groups will have the option to use the DST in dose adjustments after the operation. Each intervention group will test a different version of the DST. The control group will follow standard care practice. The randomisation ratio will be 1:1:1:1. Our primary outcome is proportion of patients within biochemical target at 8 weeks postoperatively. Secondary outcomes are distance from biochemical target at 8 weeks, mean time to achieve biochemical target, change in HRQoL, adverse events and number of days absence from work.

The study has been approved by the Norwegian Medical Products Agency (CIV-23-02-042436), The Norwegian Ethics Committee for Clinical Trials on Medicinal Products and Medical Devices (547311), and the patient protection officer at the University Hospital of North Norway. All participants will give written informed consent prior to inclusion. Results will be published open access in international peer-reviewed journals and communicated to the public through appropriate channels.

NCT06455371.