1. Hormones of the Ovary - 1– Oestrogen Lecture NO : 2nd MBBS
Dr Muhammad Ramzan

2. Ovarian hormones
Are the steroid hormones secreted by the ovaries, placenta that regulate the female reproductive system
Major Ovarian hormones are 2 : Oestrogen and Progesterone
Relaxin is another ovarian polypeptide secreted by the corpus Luteum to relax the :
Cervix and pelvic ligaments during child birth
medical dictioary.com

3. Mature follicle – the histology

4. Oestrogen – the definition
Oestrogen is one of the several steroid hormones secreted chiefly from the ovaries and placenta
It promotes the development of female secondary sex characters
webster.com

5. Oestrogen – the background
Estrogen stimulates the changes in the female reproductive organs during estrus cycle
Oestrogen is also produced in Adrenal Cortex, Testis in addition to ovaries and placenta
Is also present in vertebrates and insects

6. Oestrogen – Types and properties
There are 3 major types of oestrogens in women including
Estradiol E2 which is most potent and has :
10 -20% of the Oestrogen share
Oestrogen is available in free and bound form
Oestrogen is commonly bonded with the Steroid Binding Globulin and steroid binding albumen

7. Oestradiol - Chemical structure like CH

8. Oestrogen – synthesis and its location Cells of Maturing Follicle
Cholesterol (CH) is the primary precursor of all the steroid hormones including Oestrogen
CH is abundantly available in organs where steroid genesis takes place – Gonads, Adrenal cortex and Placenta
CH is first converted to Pregnenolone through Cholesterol Desmolase in the SER of the Granulosa and
Theca cells of the maturing follicles

9. Oestrogen – the synthesis cont.
Pregnenolone is altered to Progestogens and further to Androgens -
Androgens are the precursor to Oestrogens in ovary - β Estradiol
β - Estradiol is the active Oestrogen
This reaction is catalyzed by the Aromatase with NADPH
Small amount of Oestrogen is also produced by the:
Placenta, Adrenal cortex and Testis

10. Oestrogen – the synthesis

11. Oestrogen- the target organs
Target organs for Oestrogen are the tissues expressing Oestrogen receptors – Cytoplasmic Receptors
Major target organs are the female reproductive system
Granulosa and Theca cells of maturing Follicle
Bone cells – Osteoblasts and Osteocytes (not Osteoclasts) 3
Others include : Mammary glands; CVS, immune system and CNS

12. Oestrogen – Regulation of secretion 2 pathways - Direct and indirect
Oestrogen is regulated by 2 pathways :
Neuro endocrine / indirect pathway/ Long loop
Direct pathway/ Short loop/Pituitary ovarian axis

13. Neuroendocrine regulation/long loop pathway GnRH and GnIH
It is the interaction B/W hypothalamus and circulating levels of Oestrogen - Hypothalamus – pituitary- ovarian axis
Deficiency of Oestrogen stimulates the Hypothalamus to release GnRH which activates pituitary to Secrete Gonadotropins :
FSH and LH . Both activate ovary to↑oestrogen
Opposite is true when there is excess of Oestrogen by the secretion of GnIH from Hypothalamus (↓GnRH)

14. Oestrogen- Neuro endocrine regulation GnRH and GnIH

15. Pituitary ovarian axis Direct/short loop pathway
It is the interaction B/W the circulating levels of Oestrogen and the Pituitary gland
Deficiency of the serum level of oestrogen, stimulates Pituitary to  secrete Gonadotropins (FSH) which ↑ oestrogen level
Opposite is true when oestrogen level is high
Inhibin is a peptide hormone from the Corpus Luteum/placenta / Ovary that inhibits FSH

16. Oestrogen – Role of Inhibin

17. Estrogen – mechanism of action Formation of HRC
Oestrogen has got similar mechanism of action like rest of the Steroids
Estrogen is Lipophilic and diffuses into target tissues
Hormone binds with the Cytoplasmic receptors to form Hormone Receptor Complex – HRC
HRC increases the affinity of hormone binding at the acceptor site at the DNA strand of Nucleus

18. Oestrogen – mechanism of action cont. activation of Genes (HRE)
HRC is translocated to the acceptor site at the DNA strand in the nucleus to form Hormone Response Element (HRE)
HRE is the gene for steroids which is activated to express mRNA which leaves for cytoplasm
HRE results in the transcription of mRNA which gets its exit from nucleus to cytoplasm

19. Estrogen – Mechanism of action conti. Receptor and Hormone is set free
Translation of the mRNA leads to the synthesis of Proteins and enzymes to execute the hormonal action
HRE then leaves the acceptor site at the Nucleus and releases hormone which re circulates
The receptor is thus set free and can be reused

20. Oestrogen mechanism of action

21. Metabolic effects of Oestrogen – on female reproductive system and CVS and bones
Major action of the estrogen is on female reproductive system, however it has variety of effects on the:
CHOs , Protein and Lipid metabolism
Significant effects on bones, CVS and immune system

22. Metabolic effects on Protein and CHO metabolism hyperglycemic/ Proteolysis
Oestrogen is a weak anabolic hormone and promotes the synthesis of Steroid binding proteins - ↑Proteogenesis
Reduces muscle mass by proteolysis
Oestrogen reduces glucose uptake by the cells and increases blood glucose level - is hyperglycemic
It increases the impaired glucose tolerance risk/test

23. Metabolic effects on lipid metabolism Promotes Lipogenesis
Oestrogen promotes Lipogenesis, body fatty mass and redistribute it to the areas like:
buttocks, thighs and breast
It increases synthesis of TG and HDL- C and reduces LDL-C
It reduces cardiovascular disease risk

24. Metabolic effects on bones – Prevents Osteoporosis Reduces Osteoclastic activities
It prevents bone resorption/ osteoporosis and increases Ca deposition of bones to promotes Osteogenesis
Causes earlier fusion of epiphysis in females than males
Increases salts and water retention and BP

25. Oestrogen - Secretion abnormalities
Oestrogen may be secreted in excess or
there may be deficiency of Oestrogen secretion
Both conditions lead to the development of important clinical conditions

26. Oestrogen – the deficiency
Deficiency is commonly due to congenital diseases like : Pituitary failure and Hypogonadism or
Polycystic ovarian syndrome – PCOS
Premenupause, menopause and hysterectomy
Anorexia nervosa and
Extreme training /exercises

27. Oestrogen- excess secretion
Excess may be due to Tumours of the ovaries
Excessive intake of oestrogen for replacement therapy in the
Menopause and hysterectomy and treatment for the :
carcinoma of Breast and prostate gland