Agnus castus is known to influence the increased production of the pituitary hormone luteinising hormone, whilst reducing prolactin levels, and has therefore been studied for its affect on the menstrual cycle. Research suggests a role for agnus castus in the normalisation of the reproductive cycle, particularly where progesterone levels are low. Agnus castus may be helpful in amenorrhea (lack of menstrual periods) where the herb’s influence on luteinising hormone and prolactin may help by triggering ovulation, and therefore the subsequent build up and loss of the endometrium.