While two separate issues, there is an association between endometriosis and polycystic ovarian syndrome (PCOS) (Holoch et al., 2014; Hager et al., 2019). There isn’t much data on the incidence of endometriosis and PCOS together. One study noted it to occur in about 19.7% (Holoch et al., 2014).
Below you will find a few links and studies on PCOS.
Links:
Studies:
References
Holoch, K. J., Savaris, R. F., Forstein, D. A., Miller, P. B., Higdon III, H. L., Likes, C. E., & Lessey, B. A. (2014). Coexistence of polycystic ovary syndrome and endometriosis in women with infertility. Journal of Endometriosis and Pelvic Pain Disorders, 6(2), 79-83. Retrieved from https://www.researchgate.net/publication/269038400_Coexistence_of_polycystic_ovary_syndrome_and_endometriosis_in_women_with_infertility
Hager, M., Wenzl, R., Riesenhuber, S., Marschalek, J., Kuessel, L., Mayrhofer, D., … & Ott, J. (2019). The prevalence of incidental endometriosis in women undergoing laparoscopic ovarian drilling for clomiphene-resistant polycystic ovary syndrome: a retrospective cohort study and meta-analysis. Journal of clinical medicine, 8(8), 1210. doi: 10.3390/jcm8081210