The Effect of Levothyroxine on Lysolecithin-Induced Local Demyelination in Optic Chiasm of Male Rats

One of the significant problems in multiple sclerosis (MS) is damage to the visual system, which is the result of demyelination. Studies have suggested a link between central nervous system demyelinating diseases and thyroid disorders, and probably the treatments that increase the level of thyroid hormones are beneficial in multiple sclerosis. Therefore, in this study, the effects of levothyroxine on lysolecithin-induced demyelination/remyelination in rat's optic chiasm were evaluated.
Local demyelination was induced by injection of 2 µl lysolecithin 1% into the rat's optic chiasm. Experimental groups were control, sham, lesion (multiple sclerosis), and lesion-levothyroxine 20, 50 and 100 µg/kg (n = 9). Demyelination/remyelination was evaluated 7, 14 and 21 days after the initiation of treatment. Histomorphological changes were assessed using hematoxylin and eosin staining.
Findings: Following the injection of lysolecithin into the optic chiasm, a large demyelination was occurred, which decreased over time, indicating remyelination in this area. Following the treatment with levothyroxine, there was a significant reduction in the amount of demyelination in the treated groups compared to the multiple sclerosis group. This decrease was particularly pronounced at the dose of 100 µg/kg.
The results of this study show that injection of lysolecithin in the optic chiasm causes a reversible demyelination. Levothyroxine could produce protective effects against induced demyelination and accelerate remyelination. Therefore, thyroid hormones probably have healing effects in multiple sclerosis, although further studies are needed.