Editing Progestogen (section)

===Biosynthesis===
{{Main|Progesterone#Biosynthesis}}
[[File:Steroidogenesis.svg|thumb|450px|class=skin-invert-image|[[Steroidogenesis]], with progestogens and their precursors inside the yellow box.<ref name="HäggströmRichfield2014">{{cite journal|last2=Richfield|first2=David|year=2014|title=Diagram of the pathways of human steroidogenesis|journal=WikiJournal of Medicine|volume=1|issue=1|doi=10.15347/wjm/2014.005|issn=2002-4436|last1=Häggström|first1=Mikael|doi-access=free}}</ref>]]

Progesterone is produced from [[cholesterol]] with [[pregnenolone]] as a [[metabolic intermediate]]. In the first step in the [[steroidogenic pathway]], cholesterol is converted into pregnenolone, which serves as the [[precursor (chemistry)|precursor]] to the progestogens progesterone and 17α-hydroxyprogesterone. These progestogens, along with another steroid, [[17α-hydroxypregnenolone]], are the precursors of all other endogenous steroids, including the androgens, estrogens, glucocorticoids, mineralocorticoids, and neurosteroids. Thus, many tissues producing steroids, including the [[adrenal gland]]s, [[testicle|testes]], and [[ovary|ovaries]], produce progestogens.

In some tissues, the [[enzyme]]s required for the final product are not all located in a single cell. For example, in [[ovarian follicle]]s, cholesterol is converted to [[androstenedione]], an androgen, in the [[theca cell]]s, which is then further converted into estrogen in the [[granulosa cell]]s. Fetal adrenal glands also produce pregnenolone in some species, which is converted into progesterone and estrogens by the placenta (see below). In the human, the fetal adrenals produce [[dehydroepiandrosterone]] (DHEA) via the pregnenolone pathway.

{{Production rates, secretion rates, clearance rates, and blood levels of major sex hormones}}

====Ovarian production====
Progesterone is the major progestogen produced by the [[corpus luteum]] of the [[ovary]] in all mammalian species. [[Luteal cell]]s possess the necessary enzymes to convert cholesterol to pregnenolone, which is subsequently converted into progesterone. Progesterone is highest in the diestrus phase of the estrous cycle.

====Placental production====
The role of the placenta in progestogen production varies by species. In the sheep, horse, and human, the [[placenta]] takes over the majority of progestogen production, whereas in other species the corpus luteum remains the primary source of progestogens. In the sheep and human, progesterone is the major placental progestogen.

The equine placenta produces a variety of progestogens, primarily [[5α-dihydroprogesterone]] and [[5α,20α-tetrahydroprogesterone]], beginning on day 60. A complete luteo-placental shift occurs by day 120–150.