Female Endocrinology - overview

[biomedicool]

General endocrinology info:

• Autocrine - affects same cell
  
• Paracrine - affects a nearby cell
  
• Endocrine - affects elsewhere in the body (secreted by glands into the bloodstream)
  
• Exocrine - secreted by glands into the external environment (eg sweat, saliva)
  

Steroid hormones

• Oestrogen
  
• Progesterone 
  
• Testosterone
• Cortisol

Non-steroid hormones

• Glycoproteins (LH, FSH, TSH, hCG)
  
• Proteins (GH, prolactin, others include insulin, PTH)
  
• Peptides (oxytocin, gonadotropin releasing hormone)
• Amino acid derivatives (triiodothyronine, thyroxine (T4), adrenalin)

Anterior pituitary secretes LH and FSH (gonadotropins)

Menstrual Cycle

Follicular phase

• prepares follicles for ovulation
  
• uses LH, FSH, oestrogen
  
• FSH (from ant. pituitary) stimulates growth and maturation of several primary follicles
• each produce oestrogen which helps regenerate/prepare endometrium 
• one follicle eventually becomes dominant and the others degenerate (~day 7)

Preovulation

• Graafian follicle sends a surge of OES through bloodstream
  
• resulting LH surge prompts next stage - ovulation (~day 14)
  

Ovulation

• follicle does not enter fallopian tubes
  
• ovum erupts from follicle 
  
• fimbrae sweep up ovum, muscular contractions help guide it down the tube
  

Luteal phase

• following ovulation cells of the ruptured follicle enlarge and form the corpus luteum
• corpus luteum produces progesterone, growing for 7-8 days. if no fertilization, growth stops and progesterone slows 

Outcome 1: Fertilization 

• Egg lives for 12-24 hours
  
• takes 5 days to reach uterus (fertilization must occur in uterine tube)
• endometrial development continues with progesterone production
• formation of placenta after implantation from trophoblast - it will take over progesterone production and signal corpus luteum to degenerate into corpus albicans

Outcome 2: No fertilization 

• no blastocyst means no hCG to ovary
  
• corpus luteum stops action, degenerates
  
• drop in progesterone causes constriction of endometrial arterioles - leads to endometrial ischemia
  
• causes spongy endrometrial tissue to slough off - menstrual bleed
  

summary: