Thyroid hormone deficiency disrupts rat eye neurodevelopment

Clinical and experimental studies have highlighted the role played by thyroid hormones (TH) in neural and neuro-sensorial development. However, knowledge on TH mechanisms on the developing visual system is still incomplete. To uncover TH actions on the eyes and vision we carried out a microscopical study on the role of TH in the developing retina and optic nerve, in a rat model of controlled TH deficiency (THD). Morphometric and stereological analyses of the retina and optic nerve showed a reduction in the volume of the eye (p < 0.001) and optic nerve cross-sectional area (p < 0.001), and thinning of the retinal layers (p < 0.001). Glial development and myelination was significantly delayed in the THD optic nerves (p < 0.001), as compared to controls. The data indicate that TH play an essential role in neuro-retinogenesis. Substitutive TH therapy in critical periods, should be considered in hypothyroidism-related eye disorders as well as neurodegenerative retinal processes.

Research highlights
► Thyroid hormones (TH) are essential for nervous system development.
► TH deficiency can be induced by chemical/surgical approaches in dams and its offspring.
► Photoreceptors, ganglion cells and macroglia displayed striking developmental changes.
► Retinal mitochondria density and cristae integrity depends on TH availability.
► TH by itself or by the TH-dependent signals orchestrate the neuro-retinogenesis.