Topic 14-Sexual Differentiation-S_2011

Topic 14-Sexual Differentiation-S_2011 - 14. Sexual...

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Click to edit Master subtitle style 14. Sexual Differentiation A. The Gonadotrophins B. Synthesis & Regulation of sex steroids C. Sexual development during gestation D. Disorders of differentiation
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22 The endocrine system dominates reproduction n Required for fetus to differentiate into a normal male or female ¨ Reproductive organs ¨ Maintenance of & development of gametes ¨ Timing of reproduction n Monthly cycles n Puberty n Required to initiate & maintain pregnancy n Determine development throughout life cycle
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33 Male & female endocrine systems have many aspects in n Hypothalamic control: gonadotropin releasing hormone (GnRH) n Anterior pituitary hormones: ¨ Follicle stimulating hormone (FSH) ¨ Luteinizing hormone (LH) n Both make most of the same steroids ¨ Vastly different amounts
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Hypothalamic & pituitary control n Hypothalamic : gonadotrophin releasing hormone (GnRH) ¨ 10 amino acid peptide ¨ Gαq-coupled receptor ¨ Released in pulses n Males: 1 pulse every 1½-3 hrs n Females: 1 pulse/hr n From the gonadotrophs: LH & FSH n Both use Gαs-coupled receptors n Glycoproteins ¨ α subunits n 90 amino acids n LH=FSH=TRH ¨ β subunits n 115 amino acids n Unique n Glycosylation required for activity 44 β β β α α α FSH L H TSH
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55 GnRH from the hypothalamus stimulates L H F S H L H GnR H Anterior  Pituitary Hypothalamus FS H Ca P K C q H L H F S H Ca 2+ P K C Males & females: Same mechanism PL C P L C Ca 2 +
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66 FSH & LH control sex steroid n These pathways occur in both men & women to different extents n We’ll cover males now, females later n Features of steroid synthesis should be familiar by now (I hope) ¨ Key regulatory points n StAR n P450SCC n Unique enzymes n Steroidogenesis occurs in two cell types in the seminiferous tubules
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Sex steroid synthesis n Regulatory points ¨ StAR ¨ P450SCC ¨ 17 α-hydroxylase ¨ 17,20-desmolase ¨ Aromatase (unique) n Stimulated by LH 77 H O AB C D SCC StA R 3 β -hydroxysteroid dehydrogenase 17 α - hydroxylase O O R Pregnenolon e Progesteron e Aromatas e Estradi ol (E2) Estron e (E1) 17,20 desmolase 17 β-ηψδροξψστ εροιδ δεηψδρογ ενασε Dihydroepiando- sterone (DHEA) Androstenedi ol Testoster one Androstenedi one Synthesis of estrogens occurs in both sexes Estrogens are plural, estrone & estradiol (E2) most important in adults
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This note was uploaded on 02/22/2011 for the course PGY 452 taught by Professor Dr.baizer during the Spring '11 term at SUNY Buffalo.

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Topic 14-Sexual Differentiation-S_2011 - 14. Sexual...

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