SQOR and ulcerative colitis: We synthesize cross-system disease evidence—brain (hypoxia/ischemia, neuroinflammation), heart (divergent roles in acute ischemia–reperfusion versus chronic failure), kidney (mitochondrial dysfunction and cGAS–STING(cyclic GMP–AMP synthase–stimulator of interferon genes)–driven fibrosis), gastrointestinal tract (stage-specific effects in colorectal cancer and impaired detoxification in ulcerative colitis), bone/metabolic disorders, and the male reproductive system—highlighting SQOR’s bidirectional pathology when hydrogen sulfide is excessive or depleted.