PGR and breast cancer: However, testosterone in plasma collected during the luteal phase of the menstrual cycle was significantly associated with invasive and estrogen/progesterone-receptor positive breast cancer; ORs for women in the highest versus lowest quartiles of total testosterone were 2.0 (95% CI, 1.1 to 3.6) and 2.9 (95% CI, 1.4 to 6.0), respectively, and associations were similar for free testosterone.