SHBG and breast cancer: Women in the highest glucose quartile had a substantially higher risk of BC (RR = 1.63; P = 0.003) than those in the lowest glucose quartile. The correlation was substantial in premenopausal and postmenopausal women, and women diagnosed beyond 55 years. Women in the highest quartile of the HOMA-IR had a greater risk of BC than those in the lowest quartile (RR = 1.44). In women diagnosed after 55 years, there was a substantial increase in BC risk in the highest HOMA-IR quartile; in the same group, lower BC risk was significantly related to high SHBG.