[Dynsei]

Spearmint increases the hormones (LH, FSH) that may start the follicular phase. Those two hormones are used to increase egg release and preparation. It might be used for its estrogen effect, but it will lessen the times when prolactin and progesterone work during the luteal phase. It could have potential use for a different effect.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693613/table/tbl2680/?report=objectonly effect of herbs on hormones