Progesterone is a hormone that plays a big part in reproduction. It's made mostly in the ovaries, and the level fluctuates with your menstrual period. There is less progesterone after menopause.

Progesterone is part of hormone replacement therapy (HRT) for people who have been through menopause and still have a uterus. Possible side effects include spotting, headaches, and breast tenderness.

Estrogen and progesterone are complementary reproductive hormones. Estrogen shapes everything from puberty to menstrual cycles to bone health, and progesterone is key to the second half of the ...