5/27/2018 Kronenberg Williams Textbook of Endocrinology, 11th Ed

Kronenberg: Williams Textbook of Endocrinology, 11th ed.

SECTI! "I # Endocrinology and the $ife S%anC&'(TE) *+ # E!C)I!E C&'!-ES I! ()E-!'!C-lenn . /ra0nstein

Placental Development, 741Maternal Adaptations to Pregnancy, 742Placental Hormone Production, 745(lacental eelo%mentNormal placentation requires a coordinated series o events, !eginning "it# ertili$ation%e ertili$ation rateollo"ing unprotected regular intercourse during a single menstrual cycle is 25' to ()'%Ho"ever, inappro*imately one t#ird o conceptions, t#ere is eit#er ailure o implantation or clinical orsu!clinicalspontaneous a!ortion%+1-or t#e irst 5 days, preimplantation development ta.es place "it#in t#e allopian tu!e%

During t#is period,t#e $ygote undergoes cleavage division and, at least t#roug# t#e eig#t/cell stage, t#e!lastomeres remaintotipotential% 0n t#e 1/cell stage, dierentiation o t#e innermost cells into t#einner cellmass and t#esurrounding cells into t#e trophectoderm occurs% e inner cell mass develops into t#eetus, and t#etrop#ectoderm gives rise to t#e placenta and mem!ranes% n appro*imately day 5 or ater ertili$ation, t#e!lastocyst enters t#e uterus, !ut implantation does not occur or anot#er 1 to 2 days%0mplantation occursater t#e $ona pellucida disappears rom around t#e em!ryo%+2

0mplantation is a comple* process t#at involves apposition o t#e microvilli present ont#e trop#ectodermcells "it# pinocytes 3used microvilli on t#e endometrial cells, ollo"ed !y removal oluid !et"een t#e cellst#roug# pinocytosis !y t#e endometrial cells, a process stimulated !y progesterone%+(Progesteronesynt#esis !y t#e corpus luteum is stimulated and sustained during t#is time and or t#eirst to 7 "ee.s opregnancy !y secretion o #uman c#orionic gonadotropin 3#6 !y t#e trop#o!last cells%e #6 is irstdetected in t#e maternal serum to days ater conception%+4 Attac#ment o t#e em!ryois en#anced

t#roug# t#e e*pression o a variety o ad#esion molecules, including mucins, integrins,and trop#inin, atrop#o!last/speciic cell mem!rane ad#esion protein, as "ell as cyto.ines, gro"t#actors, and a variety otranscription actors encoded !y Homeo!o* genes%+( +5Ater t#e trop#o!last attac#es to t#e endometrium during t#e 8"indo" o implantation9 to 1) days aterovulation, t#e em!ryo invades t#e endometrium t#roug# a comple* process involvingmatri*

5/27/2018 Kronenberg Williams Textbook of Endocrinology, 11th Ed

metalloproteinases and dierentiation o t#e trop#ectoderm intocytotrophoblasts orsyncytiotrophoblasts%e syncytiotrop#o!lasts are multinucleated cells ormed !y t#e usion ocytotrop#o!lasts% ecytotrop#o!lasts orm a column o cells t#at invade t#e endometrium, orm anc#oringvilli, and enter t#e

maternal vasculature, eventually replacing t#e endot#elial layer o t#e endometrial andmyometrial spiralarterioles "it# a layer o cytotrop#o!lasts 3vascular trop#o!lasts%+ is processconverts t#e #ig#resistance,lo"/capacity uterine vessels into lo"/resistance, #ig#/volume vessels, essential orgro"t# o t#eplacenta and etus%+7 At t#e site o implantation, t#e endometrial cells undergodeciduali$ation, enlargingand increasing t#eir meta!olic activity "it# en#anced production o tissue in#i!itors ormetalloproteinase,e*tracellular matri* proteins, cyto.ines, and gro"t# actors t#at modulate t#e e*tent otrop#o!last invasion

and inluence trop#o!last unction% +( +4 +:e trop#o!last cells secrete several angiogenic proteins, including vascular endot#elialgro"t# actor,platelet/derived gro"t# actor 3PD6-, and !asic i!ro!last gro"t# actor 3!-6-, "#ic#stimulate !loodvessel development "it#in t#e villi%+ e syncytiotrop#o!lasts orm an outer layer ocells in t#e c#orionicvilli, !et"een t#e cytotrop#o!last cells and t#e maternal !lood space on t#e e*teriorsurace% nly t#reetissues separate t#e etal !lood rom maternal !lood; 31 t#e endot#elium o t#e etalvessels in t#e villi, 32connective tissue, and 3( t#e trop#o!lasts< t#is orm o placentation is reerred to as

hemochorial% us, inaddition to #6 secretion, "#ic# is responsi!le or maintaining early pregnancy,progesterone secretion,required or continuation o pregnancy ater t#e luteal/placental s#it, and t#e synt#esisand secretion oot#er #ormones and gro"t# actors 3 &a!le 2)/1 , t#e syncytiotrop#o!lasts provide t#ema=or site ortransportation o o*ygen and nutrients to and removal o "aste rom t#e etus%

T'/$E *+21 22 &)3!ES, (E(TIES, '! -)WT& 4'CT)S ()5CE /T&E ($'CE!T'&y%othalamic analog0es

6onadotropin/releasing #ormoneorticotropin/releasing #ormone>rocortin?omatostatin6ro"t# #ormone/releasing #ormone6#relinyrotropin/releasing #ormoneDopamineNeuropeptide @

5/27/2018 Kronenberg Williams Textbook of Endocrinology, 11th Ed

n.ep#alin(it0itary analog0es#orionic gonadotropinPlacental lactogen#orionic corticotropinB/ndorp#in

a/Melanocyte/stimulating #ormonePlacental variant gro"t# #ormone*ytocinSteroid hormonesstrogensProgesteronetherActivins0n#i!ins-ollistatinCela*inalcitonin

eptinParat#yroid #ormone/related proteinryt#ropoietinCenin0nterleu.insNitric o*ide&ransorming gro"t# actor/B&umor necrosis actor/apidermic gro"t# actor0nsulin/li.e gro"t# actor 00nsulin/li.e gro"t# actor 000nsulin/li.e gro"t# actor !inding protein/1

olony/stimulating actor/1Easic i!ro!last gro"t# actororticotropin/releasing #ormone !indingproteinPlatelet derived gro"t# actorFascular endot#elial gro"t# actorndot#elin/1Anadamide 3endocanna!inoidHepatocyte gro"t# actorncomodulin