The K+-lowering effects of insulin were first shown in humans around one century ago, where insulin injection lowered serum [K+]v from 4.5 to 3.2 mM in diabetic patients (Harrop 1924), to 1.8 mM in an untreated diabetic patient (Kerr 1928) and consequently used as “insulin shock therapy” to lower [K+]v in patients with schizophrenia (Keys 1938a). The gene discussed is INS; the disease is schizophrenia.