Metformin has direct effects on human ovarian steroidogenesis Rebecca Mansfield, M.B., B.S., Ray Galea, M.B., B.S., Mark Brincat, Ph.D., David Hole, B.Sc., Helen Mason, Ph.D.  Fertility and Sterility  Volume 79, Issue 4, Pages 956-962 (April 2003) DOI: 10.1016/S0015-0282(02)04925-7

FIGURE 1 Effect of a range of doses of metformin (10−6 to 10−12 M) on (A) E2, and (B) P production by granulosa cells in the presence of T (+t), FSH, or insulin. Note dose-dependent inhibition of stimulated steroid production by metformin (P < .002, ANOVA in each case). Each point represents the mean (SEM) percentage change from basal (100%) in three to six wells in three separate experiments. Absolute mean values for controls were 3.75 and 65 nmol/1,000 cells for E2 and P, respectively. C = control. Mansfield. Direct effects of metformin on the ovary. Fertil Steril 2003. Fertility and Sterility 2003 79, 956-962DOI: (10.1016/S0015-0282(02)04925-7)

FIGURE 2 Dose–reponse to metformin in luteinized granulosa cells. Each point is mean (SEM) percentage change from basal (100%) in five or six wells in (A) five and (B) six experiments. Absolute mean values for controls were 250 and 82 nmol/1,000 cells for E2 and P, respectively. Note clear dose-dependent inhibition by metformin in each case. C = control. Mansfield. Direct effects of metformin on the ovary. Fertil Steril 2003. Fertility and Sterility 2003 79, 956-962DOI: (10.1016/S0015-0282(02)04925-7)

FIGURE 3 Dose-response to metformin in dispersed theca cells incubated with (I) or without (c) insulin (10 ng/mL) with or without a range of doses of metformin (10−7 to 10−10 M). Note inhibition of basal and rostenedione at 10−7 M with no effect on P. Insulin-stimulated and rostenedione production was inhibited dose dependently by metformin with an opposite effect of equal magnitude on progesterone. Results are mean (SE) of six wells in each case. Mansfield. Direct effects of metformin on the ovary. Fertil Steril 2003. Fertility and Sterility 2003 79, 956-962DOI: (10.1016/S0015-0282(02)04925-7)

FIGURE 4 Data combined from three or four experiments in dispersed theca cells showing inhibition of basal androstenedione and P production. Absolute mean values for controls were 0.4 and 3.05 nmol/1,000 cells for androstenedione and P, respectively. Insulin (10 ng/mL) -stimulated and rostenedione was inhibited by metformin and mean P was doubled, although this change was not significant. P values: a vs. b, .038; c vs. d, .08; a vs. c, .06; e vs. f, .018; e vs. g, .03; g vs. h, .09. C = control: met = metformin. Mansfield. Direct effects of metformin on the ovary. Fertil Steril 2003. Fertility and Sterility 2003 79, 956-962DOI: (10.1016/S0015-0282(02)04925-7)