Iron deficiency and secondary anaemia were demonstrated in Macaques with naturally occurring endometriosis (Atkins et al., 2018), where duodenal, bone marrow, and liver sampling supported a systemic deficiency and correction was attempted through increased gastrointestinal absorption, as evidenced by ferroportin-1 upregulation despite high dietary iron. The gene discussed is SLC40A1; the disease is endometriosis.