Investigation of the Effect of Glycine in Patients with Hyperthyroidism Treated with Methimazole: A Two-Arm, Placebo-Controlled, Randomized Clinical Trial

To evaluate the effects of glycine supplementation alongside methimazole on anxiety, sleep quality, fatigue severity, cortisol levels, thyroid hormones, cardiovascular parameters, liver function, and hematological indices in patients with hyperthyroidism.

This is a randomized, double-blind, placebo-controlled, parallel-group clinical trial involving 60 patients allocated in a 1:1 ratio using variable block randomization. Participants and outcome assessors will be blinded. Assessments will be conducted at baseline and after the four-week intervention.

The study will be conducted at the private endocrinology clinic of a faculty member of Dezful University of Medical Sciences. Patients will be recruited through consecutive sampling.

Participants will include patients aged 18–60 years with clinically and laboratory-confirmed hyperthyroidism who have received methimazole (10–20 mg daily) for at least four weeks and provided informed consent. Proposed exclusion criteria include pregnancy and severe hepatic, renal, or cardiac disease at screening.

Intervention group (n=30): Oral glycine 1 g daily plus methimazole (10–20 mg daily). Control group (n=30): Matching placebo plus methimazole. Glycine or placebo will be administered once daily, 1–2 hours before bedtime, for four weeks.

The primary outcome is the change in anxiety score measured using the seven-item Generalized Anxiety Disorder questionnaire at baseline and after four weeks of intervention, with changes compared between the two groups.

In this study, 60 eligible patients will be randomly allocated in a 1:1 ratio to the intervention and control groups after obtaining informed consent and completing the methimazole stabilization period. The unit of randomization will be the individual patient. Randomization will be performed using variable block sizes. An independent individual, not involved in trial implementation, will generate the random allocation sequence using computer-generated random numbers. The allocation list will remain confidential, and allocation concealment will be maintained to prevent the person enrolling participants from knowing upcoming assignments.

In this study, participants, outcome assessors, and the statistical analyst will be blinded to treatment allocation. Glycine and placebo capsules will be identical in appearance, color, size, and packaging and will be coded. Allocation codes will remain confidential until completion of the final data analysis.

There is no further information.