The immunoreactivity of RBP4 in the glandular cell was significantly higher in the ovarian endometrioma than in the eutopic endometrium from controls as well as patients with endometriosis during whole menstrual phases put together (p < 0.001; p < 0.001, respectively), the proliferative phase (p = 0.018; p = 0.005, respectively), and the secretory phase (p < 0.001; p < 0.001, respectively) (Figure 2B, left). The gene discussed is RBP4; the disease is endometriosis.