Interestingly, while OXT excretion remained stable in normonatremic patients, patients later diagnosed with SIADH presented a significant increase of urinary excretion of OXT on D4 compared to D1, suggesting the concomitant existence of a syndrome of inappropriate secretion of OXT (SIOXT) in these patients (D4 vs D1: 95% CI −4.413 to −0.08275, p = 0.0428) (Fig. 1c). This evidence concerns the gene OXT and inappropriate ADH syndrome.