Aetiology

The major elements involve are thought to be:

• increased uterine activity:
  • may result from either excess synthesis of prostaglandins, or from increased myometrial sensitivity
    
    
• ischaemia:
  • hypercontraction of the myometrium may reduce blood flow causing "uterine angina" and crampy pain
    
    
• vasopressin:
  • this is often raised, and may be important as it increases both the synthesis of prostaglandins and myometrial activity
  • the role of vasopressin may help to explain why treatment with prostaglandin synthetase inhibitors is not always effective
    
    
• psychological:
  • a mother may induce expectations in a daughter that menstruation is painful as a result of her own experiences