|Jmol-3D images||Image 1|
|Molar mass||352.465 g/mol|
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Prostaglandin D2 (or PGD2) is a prostaglandin that binds to the receptor PTGDR, as well as CRTH2. It is a major prostaglandin produced by mast cells – recruits Th2 cells, eosinophils, and basophils. In mammalian organs, large amounts of PGD2 are found only in the brain and in mast cells. It is critical to development of allergic diseases such as asthma.
A 2012 research paper indicates a causal link between elevated levels of localized prostaglandin D2 and hair growth inhibition. Applied topically, the research found PGD2 prevents hair growth, and mice that were genetically inclined to produce higher levels of PGD2 had inhibited hair growth. The research also found PGD2 levels were much higher in balding scalp tissue than nonbalding scalp tissue. The paper suggested one of the receptors involved in production of PGD2, GPR44, would therefore be a therapeutic target for androgenic alopecia in both men and women with hair loss and thinning.
Because PGD2's relation to asthma has been known for several years, several drugs that seek to reduce PGD2 levels through blocking the GPR44 level are already in clinical trials.
- Cellular synthesis occurs through the arachidonic acid cascade with the final conversion from prostaglandin H2 (PGH2) done by Prostaglandin D2 synthase (PTGDS).
- In the brain, production occurs via an alternative pathway through the soluble, secreted enzyme β-trace 
- PGD2 causes a contraction of the bronchial airways. Its concentration in asthma patients is 10 times higher than in control patients, especially after it is brought into contact with allergens.
- It is involved in the regulation of reducing body temperature in sleep, and acts opposite to prostaglandin E2.
- It causes vasodilation.
- Elevated levels of PGD2 and prostaglandin D2 synthase in scalp hair follicles may be partially responsible for male pattern baldness (androgenic alopecia).
- PGD2 also plays a part in male sexual development. It forms a feedforward loop with Sox9, which is activated by the SRY of the Y chromosome. PGD2, in a different feedforward loop than FGF9, helps keep the level of SOX9 high enough to activate other genes, such as Fgf9 and Sf1, which are necessary for the development of the male reproductive system 
In August 2012, Scientists at the University of Pennsylvania announced that they had discovered Prostaglandin D2 (PGD2) was found to be present on the scalp of balding men at far higher levels than normal, preventing hair follicles from maturing and therefore stopping them from working and growing hair. Dr George Cotsarelis and his dermatological team at the University say that they are in talks with several pharmaceutical companies about developing treatments which could be available in two years.
- Saito S, Tsuda H, Michimata T (May 2002). "Prostaglandin D2 and reproduction". American Journal of Reproductive Immunology (New York, N.Y. : 1989) 47 (5): 295–302. doi:10.1034/j.1600-0897.2002.01113.x. PMID 12148545. Retrieved 2011-04-09.
- Pettipher R, Hansel TT (2008). "Antagonists of the prostaglandin D2 receptor CRTH2". Drug News & Perspectives 21 (6): 317–22. doi:10.1358/dnp.2008.21.6.1246831. PMID 18836589. Retrieved 2011-04-09.
- Morrow, JD; Parsons Wg, 3rd; Roberts Lj, 2nd (August 1989). "Release of markedly increased quantities of prostaglandin D2 in vivo in humans following the administration of nicotinic acid". Prostaglandins 38 (2): 263–74. PMID 2475889.
- Garza, Luis A. et al.,; Liu, Y.; Yang, Z.; Alagesan, B.; Lawson, J. A.; Norberg, S. M.; Loy, D. E.; Zhao, T. et al. (2012-03-21). "Prostaglandin D2 Inhibits Hair Growth and Is Elevated in Bald Scalp of Men with Androgenetic Alopecia". Science Translational Medicine 4 (126): 126ra34–126ra34. doi:10.1126/scitranslmed.3003122. ISSN 1946-6234. PMC 3319975. PMID 22440736. Retrieved 2012-03-22.
- "Clues to the cause of male pattern baldness". Nature magazine (News and Comments).
- Onoe, H. et al.,; Ueno, R; Fujita, I; Nishino, H; Oomura, Y; Hayaishi, O (2012-05-21). "Prostaglandin D2, a cerebral sleep-inducing substance in monkeys". Proceedings of the National Academy of Sciences of the United States of America 85 (11): 4082–4086. doi:10.1073/pnas.85.11.4082. PMC 280366. PMID 3163802. Retrieved 2012-05-21.
- Moniot, Brigitte; Declosmenil, Faustine; Barrionuevo, Francisco; Scherer, Gerd; Aritake, Kosuke; Malki, Safia; Marzi, Laetitia; Cohen-Solal, Ann; Georg, Ina; Klattig, Jürgen; Englert, Christoph; Kim, Yuna; Capel, Blanche; Eguchi, Naomi; Urade, Yoshihiro; Boizet-Bonhoure, Brigitte; Poulat, Francis (2009). "The PGD2 pathway, independently of FGF9, amplifies SOX9 activity in Sertoli cells during male sexual differentiation". Development 136 (11): 1813–1821. doi:10.1242/dev.032631. PMID 19429785.
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