Pathogenic variants within the gene encoding the pituitary-specific transcription factor, POU class 1 homeobox 1 (POU1F1), are associated with combined pituitary hormone deficiency (CPHD), including growth hormone, prolactin, and thyrotropin stimulating hormone deficiencies. Here, POU1F1 is linked to hyperinsulinemic hypoglycemia, familial, 4.