The Effect of Levothyroxine on Serum Levels of Interleukin 10 and Interferon‑gamma in Rat Model of Multiple Sclerosis

There is an increase in inflammatory and a reduction in anti‑inflammatory cytokines in multiple sclerosis (MS). Considering the role of thyroid hormones in the development and regulation of both neural and immune systems, the aim of this study was to evaluate the effects of levothyroxine on serum concentrations of interleukin‑10 (IL‑10) and interferon gamma (IFN‑γ) in animal models of MS.

To induce demyelination in male Wistar rats, lysolecithin was injected into the optic chiasm. Then levothyroxine was injected intraperitoneally (20, 50, and 100 µg/kg) for 21 days. Serum levels of cytokines were measured by enzyme‑linked immunosorbent assay at 7, 14, and 21 days after that.

The results showed that injection of lysolecithin to the optic chiasm only increased serum concentrations of IL‑10 compared to the sham group (P < 0.05) at 7th day, but this increase was prevented by all doses of levothyroxine. IFN‑γ was decreased significantly (P < 0.001) 21 days after. Comparing to the sham group at all sampling time and with respect to the MS group at the days 7 and 21, levothyroxine decreased serum concentrations of IFN‑γ significantly.

The results showed that thyroid hormones probably could produce protective effects against induced demyelination through affecting immune responses.