The KEGG “organismal systems” category showed involvement of various neurotransmitter and hormone signaling systems in the RP pathophysiology, such as estrogen, insulin, thyroid hormone, prolactin, oxytocin, growth hormone, neurotrophins, cholinergic, glutamate, GABA, adrenergic, and dopamine pathways. Here, PRL is linked to retinitis pigmentosa 1.