Pan D, Xu ZH, Gao Q, et al. - A retrospective study was conducted to investigate the association between penile erection and the ratio of estradiol to testosterone. Researchers included a total of 183 patients with erectile dysfunction and 52 healthy men to evaluate the association between penis base erection and tip erection. All individuals had undergone nocturnal penile tumescence tests and medical history checks and had relevant biochemical and endocrine indicators measured. They estimated the ratio of estradiol to testosterone. A negative association was noted between the E2/T ratio and penile erection, particularly at the root of the penis.