Topic 92 - Hormonal effects in the ovary; hormones of the ovary

Question 1

Words to include in hormonal effects in the ovary

Answer 1

• FSH
• LH
• PGF_2α

​FSH

• Follicle Stimulating Hormone
• Peptide hormone
• Secretion regulated by:
  
  • GnRH
  • Sexual steroids
    
    • E2
    • P4
  • Inhibin
• Role:
  
  • ​Follicle maturation
  • Stimulates E2 synthesis in ovaries

LH

• Leutinizing Hormone
• Peptide hormone
• Secretion regulatated by:
  
  • GnRH
  • Sexual steroids
    
    • Positive: E2
    • Negative: P4
• Role:
  
  • Surge center → GnRH ↑ → LH peak → Ovulation, luteinization
  • Induced ovulators: copulation → neuroendocrine reflex arch → LH peak → Ovulation, luteinization

PGF_2α

• Non-pregnant:
  
  • Production in non-pregnant uterus → lysis of corpus luteum → plasma P4 ↓
  • Endometrium release PGF_2α
    
    • Oxytocin increases PGF_2α production
    • Apotosis of luteal cells
• Endometrium → ovary
  
  • Ru: endometrial vein → a. ovarica
  • Eq: Through systemic circulation

Question 2

Words to include in hormones produced by the ovary

Answer 2

• Estrogen (E2)
• Progesterone (P4)
• Inhibin
• Relaxin
• Sexual steroids
  
  • Estrogen
  • Progesterone

Estrogen

• Estradiol - E2
• Location of production: follicle
• Stimulator of production: FSH
• Role:
  
  • Secondary sexual characeristics
  • Ovulation
    
    • Hormonal feedback mechanisms
  • Endometrium
  • Cervical and vaginal mucosa changes
  • Sexual behavior
  • Metabolism
  • Food intake
  • Water homeostasis
  • Protein sysnthesis
• Estrogen effects on the ovaries
  
  • LH-inhibiting hormone
    
    • Factor: LIF
• Stimulates follicular maturation
• Inhibin and follistatin synthesis ↑
• FSH receptor numbers on the dominant follicle ↑
• LH receptor number on the granulosa cells ↑
  
  • LIF mechanism
• Indirect effect on the ovaries
  
  • High level of E2 increases LH peak
    
    • Negative-positive feedback shift

Progesterone

• Location of production: corpus luteum
• Stimulator of production: LH
• Role:
  
  • ​Implantation and pregnancy
  • Affects vaginal epithelium and cervical mucus
    
    • Thick and impenetrable to sperm
  • Inhibits lactation during pregnancy

Tow cells-two hormones theory

• Hormones: E2 & P4
• Cells: Granulosa cells & theca cells
• Late secondary/early tertiary follicles
  
  • Sensitive to FSH/LH → maturation of follice → E2 synthesis
• Tertiary follicle
  
  • Theca cells & granulosa cells ↑
• Basal membrane
  
  • Between theca cells & granulosa cells
    
    • They have no direct contact
• LDL molcules
  
  • Main transporter of cholesterol
  • Reach granulosa cells (ø)
• Theca interna
  
  • LH-receptor
• Granulosa cells
  
  • FSH-receptor
• GnRH receptors
  
  • On granulosa cells and theca cells
  • In corpus luteum: only granulosa cells
• Early follicular phase
  
  • LH → cAMP in theca interna ↑
  • Mitochondrial cholesterol uptake ↑
  • Mitochindrion
    
    • Pregnenolon is synthesized
  • Pregenenolon
    
    • Trasported to endoplasmic reticulum (ER)
  • Pregnenolon → progesteron transformation
  • Progesteron → androstendion conversion
  • Androstendion
    
    • Diffuse to granulosa cells through basal membrane
  • Aromatase enzyme transforms androstendion/testosterone → estrone (E1) / estradiol (E2)
  • Androstenedione conversion
    
    • PRL ibhibit P4 around ovulation
• Late follicular phase
  
  • E2 production ↑
    
    • E2 stimulation: follicular maturation = dominant follicle
  • P4 apperance in circulation
  • P4 6 E2 requite LH and LH receptors for normal synthesis

Inhibin

• Location of production: dominant tertiary follicle of ovary
• Role:
  
  • ​Inhibition of FSH secretion
  • Inhibition of other developing follicles

Relaxin

• Location of production: corpus luteum
  
  • Additional production during pregnancy:
    
    • Breast
    • Placenta
    • Chorion
• Role:
  
  • ​Widens pubic bone and facilitates labor
  • Softens cervix
  • Relaxes uterine musculature

Question 3

Which hormones should be mentioned?

Answer 3

• Hormones modulating the ovarian functions:
  
  • Follicle Stimulating Hormone (FSH)
  • Luteinizing hormone
  • PGF_2α
• Hormones producted by the ovary:
  
  • Estrogens
  • Progesterone
  • Inhibin
  • Relaxin

Question 4

Hormonal effects in the ovary

Follicle stimulating hormone (FSH)

Answer 4

• Peptide hormone​
• Secretion is regulated by:
  
  • GnRH
  • Sexual steroids
    
    • ​Estrogen
    • Progesterone
  • Inhibin
• Role:
  
  • Follicle maturation
  • Stimulates estogen synthesis in the ovaries

Question 5

Hormonal effects in the ovary

Luteinizing hormone (LH)

Answer 5

• Peptide hormone
• Secretion is regulated by:
  
  • GnRH
  • Sexual steroids
    
    • ​Positive: E2
    • Negative: P4
• Role:
  
  • Surge center → GnRH ↑ → LH peak → Ovulation, luteinization
  • Induced ovulators: copulation → neuroendocrine

reflex arch → LH peak → Ovulation, luteinization

Question 6

Hormonal effects in the ovary

PGF_2α

Answer 6

• In non-pregnant uterus:
  
  • Production leads to lysis of corpus luteum → plasma P4 drop
  • Endometrium release PGF_2α on day 16-17 after ovulation
    
    • ​Oxytocin increases PGF_2α production
    • Apoptosis of the luteal cells within hours
• Ru: From endometrium directly to ovary
  
  • ​Endometrial vein → a. ovarica
• Eq: Through systemic circulation

Question 7

Hormones of the ovary

Estrogen

Answer 7

• Mostly estradiol - E2
• Sexual steroid
• Location of production: follicle
• Stimulator of production: FSH
• Role in female sexual cycle:
  
  • Secondary sexual characteristics
  • Ovulation
    
    • ​Hormonal feedback mechanism
  • Endometrial cervical and vaginal mucosa changes​
  • Sexual behavior
• Role in non-reproductive functions:
  
  • Metabolism
  • Food intake
  • Water homeostasis
  • Protein synthesis

Question 8

Hormones of the ovary

Progesterone (P4)

Answer 8

• Location of production: corpus luteum
• Stimulator of production: LH
• Role in female sexual cycle:
  
  • Implantation and pregnancy
  • Endometrium’s blood supply ↑
  • Affects vaginal epithelium and cervical mucus, making it thick and impenetrable to sperm
  • Inhibits lactation during pregnancy

Question 9

Hormones of the ovary

Inhibin

Answer 9

• Location of production: dominant tertiary follicle of the ovary
• Role:
  
  • Inhibition of FSH secretion
  • Inhbition of other developing follicles

Question 10

Hormones of the ovary

Relaxin

Answer 10

• Location of production: by corpus luteum
  
  • ​Additional production during pregnancy:
    
    • Breast
    • Placenta
    • Chorion
• Role:
  
  • Widens os pubis and facilitates labor
  • softens cervix
  • Relaxes uterine musculature

Question 11

Estrogen and progesterone production

Answer 11

Two cell - two hormones theory

• Cells:
  
  • Granulosa cells
  • Theca cells
• Hormones:
  
  • Estrogen
  • Progesterone
• Late secondary / early tertiary follicles:
  
  • ​Sensitive to FSH/LH → further maturation of follicle → E2 synthesis
• Tertiary follicles
  
  • ​Theca cellsandgranulosa cells ↑
  • Zona pellucida + membrana hyaloidea are thick
• Basal membrane:
  
  • ​There is no direct contact between theca interna and granulosa cells
• Theca interna: ​LH-receptor
• Granulosa cells: FSH-receptor
• Granulosa cells of pre-ovulatory follicles & theca cells: GnRH-receptor
  
  • ​In corpus luteum, GnRH-receptorsare only present ongranulosa cells
• Early follicular phase
  
  1. ​​In presence of LH, cAMP in theca interna cells ↑
  2. Mitochondrial cholesterol uptake ↑
  3. In mitochondria, pregenenlon is synthesized
  4. Pregnenolon is transported to the endoplasmic reticulum (ER)
  5. Pregnenolon → progesteron transformation
  6. Progesteron → androstendion conversion
  7. Androstendion diffuses to the granulosa cells through the basal membrane
  8. Aromatase enzymes transformes the androstendion / testosterone → estrone (E1) / estradiol (E2)
• ​Ru: granulosa cells are also able to synthesize pregnenolon
• Late follicluar phase
  
  • ​E2 production ↑
    
    • E2 stimulation: folliclar maturation = dominant follicle
  • P4 in circulation
  • E2 and P4 requires LH and LH-receptors for the normal synthesis
  • LH is neccessary to transform granulosa cells → granulosa-lutein cells
  • Prolactin is able to block the transformation of P4 in theca cells

Question 12

Estrogen effects on the ovaries

Answer 12

• LH-inhbiting hormone
  
  • ​Factor: LIF
• Stimulates follicular maturation
• Inhibin and follistatin synthesis ↑
• FSH receptor on the dominant follicle ↑
• LH receptor on the granulosa cells ↑
  
  • LIF mechanism
• Indirect effect on the ovaries:
  
  • High level of estrogen increases the LH peak
    
    • ​Negative-positive feedback shift