Relationship between serum testosterone and sex hormone binding globulin in menstruating and postmenopausal women

The relationship between total testosterone (T), sex hormone binding globulin (SHBG) and calculated non-SHBG-bound testosterone (NST) was studied in randomly collected blood samples from healthy menstruating (n = 61) and postmenopausal (n = 65) women. In 12 of the menstruating women, blood samples were also collected more frequently during the menstrual cycle. Total T and SHBG were positively correlated in menstruating women in random samples as well as during different phases of the menstrual cycle, but not in postmenopausal women. Upper and lower limits of NST were independent of SHBG in menstruating but not in postmenopausal women. The data are at variance with the common concept about SHBG regulation and suggest a kind of compensatory mechanism in order to maintain a constant androgen homeostasis in menstruating but not in postmenopausal women. Consequently, supranormal total T or subnormal SHBG values do not necessarily indicate hyperandrogenicity in normally menstruating women.