n.
Pronunciation: pr ō - ' jes-t ə - ˌ r ō n
Function: noun
Etymology: proge stin + -sterone
Date: 1935
: a female steroid sex hormone C 21 H 30 O 2 that is secreted by the corpus luteum to prepare the endometrium for implantation and later by the placenta during pregnancy to prevent rejection of the developing embryo or fetus also : a synthetic steroid resembling progesterone in action