Progesterone resistance in endometriosis is a known fact. The progestin derivatives used in endometriosis cause decidualization and atrophy of ectopic foci. Moreover, they inhibit neo-angiogenesis, provide suppress expansile/destructive growth facilitated by matrix metalloproteinases, and implantation of ectopic foci. The effect of drugs containing the estrogen-progesterone combination is mainly based on the inhibition of ovulation, decidualization and atrophy of ectopic foci. In estrogen-progesterone mechanism, it is known that estrogen has a progesterone receptor-enhancing effect, which may make progesterone more potent. Based on this, the investigators hypothesized that estrogen added to progesterone could lead to a further reduction in endometrioma size by various mechanisms which probably include the increased progesterone sensitivity in endometriosis. In addition, the investigators hypothesized that this therapy can alleviate the destructive effect of endometriomas on the ovarian reserve.

Inclusion Criteria:

1. Study Group: At least one endometrioma greater than 3 cm, between 18-40 years of age, without surgical indication at the time of diagnosis, occasionally and intermittently controlled pain with NSAIDs or no pain symptom
2. Control Group: Patients with reproductive age without any ovarian cysts

Exclusion Criteria:

• suspicion of malignancy, irregular mentrual period, endocrine diseases, drug intake that may affect ovarian reserve in the last 6 months (i.e GnRH agonists), previous ovarian surgery, AMH levels under 2 ng/ml.