Sex differences due to gonadal hormone effects in adult hypothalamic astrocytes. In four core genotype (FCG) mice, control astrocytes from XYM mice synthesized significantly less progesterone (P < 0.05) than control astrocytes from XXF, XYF and XXM mice. XXF and XYF astrocytes responded to estradiol (1 nmol/l) with increased progesterone synthesis (P < 0.05 versus their control), but XXM and XYM astrocytes did not (P > 0.05 versus their control). *Significantly different compared with all other controls (P < 0.05, ANOVA with Tukey-Fisher least significant difference post hoc test). †Significantly greater progesterone synthesis with 1 nmol/l estradiol compared with the control (P < 0.05, ANOVA with Tukey-Fisher least significant difference post hoc test).