X-linked central congenital hypothyroidism with late-onset testicular enlargement (Monarch Disease Ontology identifier MONDO_0010475) is an X-linked recessive syndrome caused by loss-of-function mutation(s) in IGSF1, encoding immunoglobulin superfamily member 1. This condition can result in central hypothyroidism, macroorchidism, delayed puberty, and variable prolactin deficiency. Also known as: CHTE, IGSF1 deficiency syndrome, Immunoglobulin superfamily member 1 deficiency syndrome, X-linked central congenital hypothyroidism with late-onset macroorchidism, central hypothyroidism and testicular enlargement, hypothyroidism Central and testicular enlargement, hypothyroidism, central, and testicular enlargement, X-linked recessive.