The DIPNET team (UMR1251 AMU-INSERM) reports in a transatlantic collaborative study* the first splice-disruptive variants of POU1F1, the gene that encodes the pituitary-specific transcription factor Pit-1, associated with congenital hypopituitarism. Four missense variants were found, that shift splicing to favor the repressor POU1F1 beta isoform. Using a high throughput assay, a total of 132 variants were identified that cause exon skipping, isoform switching, or cryptic isoform use. With this splicing effect catalog, additional families with hypopituitarism were evaluated and two unrelated patients carrying synonymous POU1F1 variants that affect its splicing without changing the amino acid sequence were identified. This study underscores the importance of evaluating splicing defects as a disease mechanism