Polycystic ovary syndrome (PCOS) is a common reproductive disease with high heterogeneity. The role of excess
androgen in PCOS etiology remains disputed, since around 20%-50% of PCOS women do not display hyperandrogenemia. The microenvironment of the ovary critically influences follicular development. In the present study, we assessed the role of
androgen in PCOS by investigating whether excessive follicular fluid
androgen was present in PCOS patients with normal serum
androgen levels and influenced by follicular fluid
insulin resistance (IR). Follicular fluid samples of 105 women with PCOS and 105 controls were collected. Levels of
steroid hormones,
glucose and
insulin in the follicular fluid were examined and compared with data from serum biochemistry tests. We found that 64.9% (63/97) of PCOS patients with normal serum
androgen levels displayed abnormally high follicular fluid
androgen level. The follicular fluid
androgen level was positively correlated with follicular fluid IR within a certain range and follicular fluid
estrogen-to-
testosterone (E2/T) ratio was significantly reduced in these patients. These results indicated that there existed a subgroup of PCOS patients who displayed excessive follicular fluid
androgen and IR despite their normal circulating
testosterone (T) levels. Our study highlights the importance of ovary
hyperandrogenism and IR in the etiology of PCOS.