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Reproductive Endocrinology

Reproductive Endocrinology. Males Females Fertilization Pregnancy & Placenta Childbirth Lactation. 1. Males. 2. Female. Feedback. At low circulating levels , estrogens exert negative feedback on LH and FSH secretion;

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Reproductive Endocrinology

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  1. Reproductive Endocrinology • Males • Females • Fertilization • Pregnancy & Placenta • Childbirth • Lactation

  2. 1. Males

  3. 2. Female

  4. Feedback • At low circulating levels, estrogens exert negative feedback on LH and FSH secretion; • At very high levels estrogens exert positive feedback on LH and FSH secretion. From this positive feedback comes the ovulatory surge.

  5. 3. Fertilization

  6. Acrosome Fertilization In the Fallopian tubes Many sperm necessary for fertilization to occur

  7. PREGNANCY

  8. Placenta  by end of first trimester c.l. degenerates and placenta takes over as endocrine organ of pregnancy Implantation

  9. C.l.  produces high levels of progesterone and estrogen Steroids feedback on pituitary, & suppress LH & FSH Secretion: no FSH  no new cycle, OK no LH  no c.l.!!! OOPS Blactocyst/trophoblast take over  produce LH like gonadotrophin to support the c.l. hCG Corpus luteum supported by hCG continues to produce steroids for the first trimester.

  10. Placenta • Transport of molecules between mother & fetus • Endocrine organ Placental hormones 1. Steroids: Progestins & Estrogens 2. Protein hormones: chorionic gonadotropin placental lactogens relaxin

  11. Protein hormones Chorionic gonadotropins prevent luteal regression provide maternal recognition of fetus Placental lactogens similar to PRL and GH  functions not well known (metabolism, c.l…) Relaxin  synergistic with progesterone in maintaining pregnancy. Prevents uterine contractions during pregnancy Relaxes pelvic ligaments at parturition

  12. Parturition Trigger baby stimulates production of prostaglandins by endometrium (PG-F2a) • Increase contractions in myometrium • “Ripen” the cervix: break down collagen and • make cervix softer

  13. CHILDBIRTH

  14. 24 weeks 6 wks 9 wks

  15. Baby moving down birth canal stretches vagina reflex that induces oxytocin release Oxytocin causes powerful contractions Birth!

  16. Lactation Estrogen  breast development during pregnancy PRL  development of milk secreting glands  milk production PRL increases during pregnancy but is blocked by E2 At birth  E2 levels drop and PRL induces milk production

  17. Suckling Baby suckling Reflex release of OXYTOCIN & PRL Oxytocin causes contraction of the walls of milk ducts PRL induces milk production PRL inhibits gonadotropin production (no ovulation/cycle during lactation)

  18. …one last thought…

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