Previous studies have shown that degenerating retinas in mouse models of retinal degeneration show increased expression of TH receptor/Thrb2 (Ma et al., 2017) and iodothyronine deiodinases/Dio2 (Yang et al., 2016), suggesting that TH signaling activity is likely locally elevated in degenerating retinas. Here, DIO2 is linked to retinal degeneration.