Main Entry:

pro·ges·ter·one

Pronunciation:

\prō-ˈjes-tə-ˌrōn\

Function:

noun

Etymology:

progestin + -sterone

Date:

1935

: a female steroid sex hormone C₂₁H₃₀O₂ 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