IGSF1 and cyclic hematopoiesis: In addition to central CH, IGSF1 deficiency in males leads to a heterogeneous phenotype, including macroorchidism, delayed pubertal testosterone rise (but a normal timing of testicular growth) and in some cases other pituitary hormone deficiencies, namely low serum prolactin and growth hormone (GH) deficiency (in childhood) (Table 2) (37, 38).