Progesterone is a female sex hormone which is produced by the ovaries during the luteal phase (15th-28th day) of the menstrual cycle. It is a crucial hormone required for maintaining normal function of the female reproductive system. Progesterone is also produced in placenta during pregnancy. In normal menstruating women, low level of progesterone is associated with irregular or heavy bleeding and is also responsible for miscarriage. The level of progesterone declines with the onset of menopause and gives rise to various health complications associated with it. This is why progesterone is used as a key hormone used in hormone replacement therapy.