Direct Thiazolidinedione Action in the Human Ovary: Insulin-Independent and Insulin-Sensitizing Effects on Steroidogenesis and Insulin-Like Growth Factor Binding Protein-1 Production

PPAR-gamma agonists directly stimulate progesterone and IGFBP-1 production, inhibit estradiol and testosterone production, abolish insulin-induced stimulation of testosterone production and insulin-dependent stimulation of estradiol production in the presence of FSH, and enhance insulin-induced inhibition of IGFBP-1 production in human ovarian cells. PPAR-gamma represents a novel system of ovarian regulation.