Background: Subclinical hypothyroidism is associated with metabolic disturbances and reduced quality of life. However, the combined effects of exercise and herbal supplements have been less investigated. The aim of this study was to examine the combined effects of HIIT and Nasturtium officinale supplementation on the hepcidin–ferritin axis, thyroid and renal indices, and quality of life in patients with subclinical hypothyroidism.

Methods: In this single blind randomized clinical trial, 40 overweight patients with subclinical hypothyroidism with a mean age of 41.6 ± 5.30 years were randomly assigned to four equal groups: exercise, exercise + supplementation, supplementation, and control. The exercise groups performed HIIT three sessions per week, and the supplementation groups consumed 500 mg of Nasturtium officinale extract daily for eight weeks. Before and after the intervention, serum levels of hepcidin, ferritin, hemoglobin, TSH, T3, T4, urea, and creatinine were measured, and quality of life was assessed using the SF‑36 questionnaire. Data were analyzed using ANCOVA and the LSD post hoc test in SPSS (P < 0.05).

Findings: After the intervention, decreases in hepcidin, urea, creatinine, and TSH and increases in iron, hemoglobin, ferritin, T3, T4, and quality of life were observed in all intervention groups (P < 0.05). However, these changes were greater in the exercise + supplementation group compared with other groups (P < 0.05).

Discussion: HIIT combined with Nasturtium officinale supplementation may improve iron homeostasis, thyroid and renal function, and quality of life in patients with subclinical hypothyroidism and could be recommended as a complementary intervention.