Although IGSF1 loss has been noted in human hypothyroidism, this is the first reported phenotype in a family with copy number duplication in the region.
Based on a patient with a full deletion of IGSF1 clinically followed from neonate to adulthood, we investigated a common pituitary origin for hypothyroidism and macroorchidism, and the role of IGSF1 as regulator of pituitary hormone secretion.