Also, MMP-26 (endometase) seems to co-variate with the estrogen receptor α (ER-α), as studies have demonstrated high mRNA MMP-26 levels at mid-cycle and patients with endometrial hyperplasia, while sharply declining levels were demonstrated in the second phase of the cycle and in patients with endometrial carcinoma [21,34,35,36]. The gene discussed is ESR1; the disease is endometrial carcinoma.