Difference in Circulating Irisin Levels before and after Treatment of Overt Hypothyroidism in Newly Diagnosed Autoimmune Hashimoto’s Thyroiditis

Background: Thyroid hormones have critical roles in regulating metabolism, muscle function, and thermogenesis. Autoimmune Hashimoto’s thyroiditis is the leading etiology of overt hypothyroidism and is often associated with metabolic alterations.
Objective: This study aimed to assess differences in circulating irisin concentrations prior to and following management of overt hypothyroidism in newly identified patients with Hashimoto’s thyroiditis and to explore associations between irisin concentrations and thyroid function indicators.
Methods: This case-control research, performed at the Internal Medicine Clinic in both Benha and Zagazig Universities. It included 12 healthy participants and 12 cases with overt hypothyroidism from Hashimoto thyroiditis. Serum levels of irisin, free thyroxine (fT4), anti-thyroid peroxidase (anti-TPO), TSH, free triiodothyronine (fT3), anti-thyroglobulin (anti-TG) and creatine kinase (CK) have been determined. Measurements were repeated after achieving euthyroid status following individualized levothyroxine therapy.
Results: At baseline, hypothyroid patients showed significantly greater anti-TPO, anti-TG, TSH, and CK concentrations and lower fT4, fT3, and irisin levels in comparison with controls (all p-values were below 0.001). After treatment, irisin concentrations significantly increased in the patients. Irisin was negatively related to anti-TPO, TSH, CK and anti-TG, and positively related to free thyroxine.
Conclusion: Cases with overt hypothyroidism from Hashimoto’s thyroiditis had reduced circulating irisin levels, which significantly increased after restoring euthyroidism. The findings suggest that irisin level reflects thyroid hormone status and may serve as a metabolic biomarker in hypothyroid patients. Larger investigations are warranted to validate these results and clarify underlying mechanisms.