Abstract Background: It has long been known that chemotherapy can result in premature menopause, causing follicular senescence and estrogen depletion with associated hot flashes and mood alterations. What is less well appreciated is whether the stroma of the ovary is equally impacted after chemotherapy, resulting in androgen deprivation. The aim of this pilot study was to evaluate whether androgen levels are adversely affected after chemotherapy and whether this is associated with unwanted symptoms. Methods: Women who were premenopausal, newly diagnosed with breast cancer, and about to undergo adjuvant chemotherapy were followed longitudinally. Women with adrenal insufficiencies, taking steroids, oral contraceptives, or had had previous chemotherapy were excluded. Self report questionnaires regarding sexual function, fatigue, mood, menstrual symptoms; menstrual diaries; and blood were collected at 4 points: before treatment, mid chemotherapy, post chemotherapy and 6 months later. Serum concentrations of dehydroepiandrosterone sulfate (DHEA-S) (adrenal hormone), bioavailable testosterone (bioT), androstenedione (Adione) (stromal hormone), estrone (E1), estradiol (E2) (follicular hormone), sex hormone binding globulin (SHBG), and follicle stimulating hormone (FSH) were evaluated. Descriptive statistics, comparisons of means by two sided t-tests and Pearson correlation coefficients were computed. Six month post treatment data are reported. Results: 24 women were accrued and 21 provided serum and questionnaires through 6 months. All sex steroid hormones decreased during chemotherapy and did not return to baseline by 6 months for the group as a whole. At 6 months, 14 women were postmenopausal per FSH, E2 and menstrual diaries and 7 had resumed menses. There were no significant differences in hormone concentrations at baseline between women who ended up menopausal from those who resumed menses. However, at 6 months, postmenopausal women had significantly lower concentrations than premenopausal women of E2 (289 pg/ml pre- 9 pg/ml post), E1 (132 pg/ml pre- 22 pg/ml post), and Adione (102 ng/dL pre- 56 ng/dL post), but not DHEA-S or bioT (all p < .01). E2 was significantly correlated with Adione (R = .47 p = .03), and E1 (R = .57, p = .007). Low to moderate correlations were found between hormone concentrations and symptoms. The use of tamoxifen was significantly, and negatively correlated with the total score on the Female Sexual Function Index (r = −.572, p = .005), indicating worse sexual function for women on tamoxifen. Conclusion: These data support the hypothesis that the post chemotherapy ovary suffers both follicular and stromal dysfunction, as noted by lower Adione, which is specific to the ovarian stroma. Adione concentrations in the postmenopausal group women are similar to published reports of women post oophorectomy. This is the first longitudinal study we are aware of to evaluate ovarian stromal function in women undergoing chemotherapy. This total hormone depletion may be why women experiencing chemotherapy induced menopause report severe and distressing menopausal symptoms such as hot flashes. Estrogen is often implicated, but androgen deprivation in this population should be taken into consideration when planning interventions to improve health related quality of life. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-11-01.