What the key clinical trials found
The most cited research comes from the Höfling et al. series out of the University of São Paulo:
The most significant clinical trial was conducted by Höfling et al. (2013) in a randomized, placebo-controlled study involving 43 patients with Hashimoto's thyroiditis. Patients receiving low-level laser therapy showed a significant reduction in levothyroxine dosage requirements, with 47% of treated patients able to discontinue thyroid medication entirely during the 9-month follow-up period, compared to none in the placebo group.
A follow-up study by the same group (Höfling et al., 2020) extended the observation period to 6 years. The benefits persisted — patients who had received the therapy maintained improved thyroid function and many continued to require lower medication doses compared to baseline.
A 2020 study also concluded that photobiomodulation with near-infrared light led to a 50% reduction in levothyroxine usage, a 53% increase in T3 levels, and a 73% reduction in TPOAb levels three months post-treatment.