Editing Progesterone (section)

===Reproductive system===
[[File:Endometrium ocp use3.jpg|thumb|right|[[Micrograph]] showing changes to the [[endometrium]] due to progesterone ([[decidualization]]) [[H&E stain]].]]
Progesterone has key effects via non-genomic signalling on human sperm as they migrate through the female reproductive tract before [[fertilization]] occurs, though the receptor(s) as yet remain unidentified.<ref name="pmid17447210">{{cite journal | vauthors = Correia JN, Conner SJ, Kirkman-Brown JC | title = Non-genomic steroid actions in human spermatozoa. "Persistent tickling from a laden environment" | journal = Seminars in Reproductive Medicine | volume = 25 | issue = 3 | pages = 208–219 | date = May 2007 | pmid = 17447210 | doi = 10.1055/s-2007-973433 | s2cid = 260318879 }}</ref> Detailed characterisation of the events occurring in sperm in response to progesterone has elucidated certain events including intracellular calcium transients and maintained changes,<ref name="pmid10837122">{{cite journal | vauthors = Kirkman-Brown JC, Bray C, Stewart PM, Barratt CL, Publicover SJ | title = Biphasic elevation of [Ca(2+)](i) in individual human spermatozoa exposed to progesterone | journal = Developmental Biology | volume = 222 | issue = 2 | pages = 326–335 | date = June 2000 | pmid = 10837122 | doi = 10.1006/dbio.2000.9729 | doi-access = free }}</ref> slow calcium oscillations,<ref name="pmid14606954">{{cite journal | vauthors = Kirkman-Brown JC, Barratt CL, Publicover SJ | title = Slow calcium oscillations in human spermatozoa | journal = The Biochemical Journal | volume = 378 | issue = Pt 3 | pages = 827–832 | date = March 2004 | pmid = 14606954 | pmc = 1223996 | doi = 10.1042/BJ20031368 }}</ref> now thought to possibly regulate motility.<ref name="pmid15322137">{{cite journal | vauthors = Harper CV, Barratt CL, Publicover SJ | title = Stimulation of human spermatozoa with progesterone gradients to simulate approach to the oocyte. Induction of [Ca(2+)](i) oscillations and cyclical transitions in flagellar beating | journal = The Journal of Biological Chemistry | volume = 279 | issue = 44 | pages = 46315–46325 | date = October 2004 | pmid = 15322137 | doi = 10.1074/jbc.M401194200 | doi-access = free }}</ref> It is produced by the ovaries.<ref name=Marieb>{{cite book | vauthors = Marieb E | title = Anatomy & physiology | publisher = Benjamin-Cummings | page= 903 | year = 2013 | isbn = 9780321887603 }}</ref> Progesterone has also been shown to demonstrate effects on octopus spermatozoa.<ref name="pmid11335951">{{cite journal | vauthors = Tosti E, Di Cosmo A, Cuomo A, Di Cristo C, Gragnaniello G | title = Progesterone induces activation in Octopus vulgaris spermatozoa | journal = Molecular Reproduction and Development | volume = 59 | issue = 1 | pages = 97–105 | date = May 2001 | pmid = 11335951 | doi = 10.1002/mrd.1011 | s2cid = 28390608 }}</ref>

Progesterone is sometimes called the "[[Pregnancy hormones|hormone of pregnancy]]",<ref name="colostate">{{cite web | url = http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/endocrine.html | title = Placental Hormones | access-date = 12 March 2008 | last = Bowen | first = R. | date = 6 August 2000 | archive-date = 17 May 2007 | archive-url = https://web.archive.org/web/20070517165244/http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/endocrine.html | url-status = dead }}</ref> and it has many roles relating to the development of the fetus:
* Progesterone converts the [[endometrium]] to its secretory stage to prepare the uterus for implantation. At the same time progesterone affects the [[vaginal epithelium]] and [[Cervix#Cervical mucus|cervical mucus]], making it thick and impenetrable to [[sperm]]. Progesterone is anti-[[mitosis|mitogenic]] in endometrial epithelial cells, and as such, mitigates the tropic effects of [[estrogen]].<ref name="pmid25406186">{{cite journal | vauthors = Patel B, Elguero S, Thakore S, Dahoud W, Bedaiwy M, Mesiano S | title = Role of nuclear progesterone receptor isoforms in uterine pathophysiology | journal = Human Reproduction Update | volume = 21 | issue = 2 | pages = 155–173 | year = 2014 | pmid = 25406186 | pmc = 4366574 | doi = 10.1093/humupd/dmu056 }}</ref> If [[Pregnancy|pregnancy]] does not occur, progesterone levels will decrease, leading to [[menstruate|menstruation]]. Normal menstrual bleeding is progesterone-withdrawal bleeding. If ovulation does not occur and the [[corpus luteum]] does not develop, levels of progesterone may be low, leading to [[Dysfunctional uterine bleeding#Anovulatory DUB|anovulatory dysfunctional uterine bleeding.]]
* During implantation and [[gestation]], progesterone appears to decrease the maternal [[immune system|immune]] response to allow for the acceptance of the pregnancy.<ref name="pmid27662646">{{cite journal | vauthors = Di Renzo GC, Giardina I, Clerici G, Brillo E, Gerli S | title = Progesterone in normal and pathological pregnancy | journal = Hormone Molecular Biology and Clinical Investigation | volume = 27 | issue = 1 | pages = 35–48 | date = July 2016 | pmid = 27662646 | doi = 10.1515/hmbci-2016-0038 | s2cid = 32239449 }}</ref>
* Progesterone decreases contractility of the uterine [[smooth muscle]].<ref name="colostate"/> This effect contributes to prevention of [[preterm labor]].<ref name="pmid27662646" /> Studies have shown that in individuals who are pregnant with a single fetus, asymptomatic in the prenatal stage, and at a high risk of giving pre-term birth spontaneously, vaginal progesterone medication has been found to be effective in preventing spontaneous pre-term birth. Individuals who are at a high risk of giving pre-term birth spontaneously are those who have a short cervix of less than 25&nbsp;mm or have previously given pre-term birth spontaneously. Although pre-term births are generally considered to be less than 37 weeks, these studies found that vaginal progesterone is associated with fewer pre-term births of less than 34 weeks.<ref name="pmid35168930">{{cite journal | vauthors = Care A, Nevitt SJ, Medley N, Donegan S, Good L, Hampson L, Tudur Smith C, Alfirevic Z | display-authors = 6 | title = Interventions to prevent spontaneous preterm birth in women with singleton pregnancy who are at high risk: systematic review and network meta-analysis | journal = BMJ | volume = 376 | pages = e064547 | date = February 2022 | pmid = 35168930 | pmc = 8845039 | doi = 10.1136/bmj-2021-064547 }}</ref>
* A drop in progesterone levels is possibly one step that facilitates the onset of [[labor (childbirth)|labor]].{{cn|date=February 2025}}
* In addition, progesterone inhibits [[lactation]] during pregnancy. The fall in progesterone levels following delivery is one of the triggers for milk production.{{cn|date=February 2025}}

The [[fetus]] [[metabolize]]s placental progesterone in the production of [[adrenal]] steroids.<ref name="pmid30763313"/>