Pharmacokinetics

Absorption of oestrogens may be via several routes:

• gastrointestinal tract - well absorbed:
  • endogenous oestrogens are immediately prone to a large amount of first pass metabolism
  • synthetic oestrogens are less prone to degradation
• topically:
  • well absorbed from skin
  • good absorption from mucous membranes e.g. vaginal via pessaries

Transport of oestrogens occurs after binding to:

• albumin
• sex steroid-binding globulin

Excretion of oestrogens is via oestriol. It is converted to a sulphate or glucuronide and then passed into urine.