Contraindications specific to oral estrogen

After excluding contraindications to all systemic MHT, consider whether any contraindications specific to oral estrogen are present. These include:

  • risk factors for venous thromboembolism, including obesity, smoking and thrombophilia
  • risk factors for cardiovascular disease, including previous cardiovascular disease, insulin resistance, diabetes, obesity, hypertension (even if controlled), smoking
  • elevated triglycerides (may be exacerbated by oral estrogen elevating risk of complications such as pancreatitis)
  • liver disease or gallbladder disease (less severe disease than that warranting contraindication to all MHT)

If any of these contraindications to oral estrogen is present, transdermal estrogen is recommended. Transdermal estrogen avoids first-pass metabolism in the liver, and therefore has less impact than oral estrogen on clotting factors, biliary function, other proteins and triglycerides. Transdermal MHT does not significantly increase VTE risk; transdermal doses of 50 micrograms daily or below do not elevate stroke risk.

Note: Transdermal estrogen confers less risk of venous thromboembolism, hypertriglyceridaemia and stroke than oral estrogen.

Relative contraindications to oral estrogen include malabsorption (may result in breakthrough bleeding or inadequate symptom relief) and low libido (oral estrogen increases sex hormone–binding globulin [SHBG], which reduces bioavailable testosterone and may exacerbate low libido). Transdermal estrogen is preferred to avoid these complications. The vaginal ring is an alternative for individuals younger than 50 years with malabsorption, but it increases SHBG, so may reduce libido in a similar manner to oral estrogen.