NGF and Dysmenorrhea: And, the emergence of new nerves and blood vessels in the lesion sites is also one of the contributing factors to the occurrence of dysmenorrhea [21], Additionally, EMs tissue can promote the expression of neurotrophic factors (NGF, BDNF, NT4, and NT5) to regulate pain associated with EMs [22, 23].The causal relationship between the frequency of dysmenorrhea and EMs remains unclear.