due to the hormonal fluctuations during pregnancy and postpartum [4]. One indication for this is the hypothesis of ovarian-steroid-withdrawal as the cause of postpartum depression [22, 44]. Estrogen levels increase by over 1000-fold shortly before parturition compared to their normal values and then drop dramatically after parturition [45]. This sudden drop in estradiol and progesterone is believed to be an important factor in the postpartum blues, a phenomenon which is observed in 80% of women shortly after birth and which can convert to PPD [5, 46]. This is consistent with a report that women suffering from polycystic ovary syndrome, which is associated with low estrogen levels, have an increased risk for mood disorders [47]. These findings suggest that low levels or sudden declines in estradiol and/or progesterone levels may predispose vulnerable women to depression. Besides the fluctuations in gonadal hormones during pregnancy and postpartum, it is important to note that the hypothalamic–pituitary–adrenal axis (HPA) also undergoes significant changes in the postpartum period. For example, pregnancy-related steroid hormones and peptides, such as oxytocin, dampen the reactivity of the HPA axis during pregnancy. Furthermore, there is evidence that cortisol, adreno-cortico-tropic-hormone, corticotropin releasing hormone, and corticosterone binding globulin (CBG) levels are altered significantly
