Effects of Probiotics on Thyroid Function and Fatigue in Hypothyroid Patients: A Randomized Placebo Controlled Trial

Objective: Several studies have reported a correlation between gut dysbiosis and primary hypothy roidism. Additionally, probiotics supplementation has been found to alleviate symptoms of hypothyroidism and its associated side effects. This study aimed to investigate the effect of probiotics supplementation on thyroid function and fatigue severity score (FSS) in hypothyroid patients.

Methods: This trial enrolled 80 patients with hypothyroidism. Participants were randomly allocated into intervention and control groups receiving 500 mg/day probiotic (n= 40) or placebo capsules (n=40) for 12 weeks. Besides FSS and thyroid function factors as primary outcomes, anthropometric indices, levels of c-reactive protein (CRP), liver function markers, and lipid profile were also assessed during follow-up.

Results: At baseline, the 2 groups were homogeneous regarding demographic, anthropometric, and clinical parameters except for age, which differed significantly (P=.026). After a 12-week intervention, both groups showed a significant decrease in FSS (P < .001), but the reduction was more effective in the intervention group (P=.002). A significant between-group difference was observed for Body Mass Index (BMI) (P=.007) and Free-T3 (P=.014), with the intervention group showing greater reduction in BMI and more Free-T3 changes at the end of the intervention compared to the controls. A significant decrease in CRP levels occurred only in the intervention group (P=.005). Furthermore, significant improvements occurred in waist circumference (P=.015), free-T4 (P=.012), triglyceride (P=.004), and low-density lipoprotein (P= .001) in the intervention group from pre- to post-treatment.

Conclusion: Probiotic supplementation had beneficial effects on fatigue and thyroid function in hypothyroid patients. Further trials with larger sample sizes and prolonged durations are needed for validation.

Cite this article as: AkbariRad M, Mazloum Khorasani Z, Hemmatpur A, et al. Effects of probiotics on thyroid function and fatigue in hypothyroid patients: A randomized placebo controlled trial. Endocrinol Res Pract. Published online June 3, 2025. doi 10.5152/ erp.2025.24604.