PGR and meningioma: More importantly, we further found significant interaction between expression of PR and NF2, in which females who had low both expression of PR and NF2 had significantly increased risk of meningioma when compared to those who had higher expression of PR and NF2. These findings suggest that long exposure to exogenous progesterone may increase the risk of developing meningioma through lowering the expression of PR and NF2.