Lower blood levels of sex steroids and higher concentrations of prolactin and its antigonadotrophic activity in males affected with Parkinson's disease may result in a bigger susceptibility to the disease in men. The level of hormones may influence patients' cognition, mood and quality of life.

There may be a relationship between the lifetime average endogenous oestrogen level and the susceptibility to develop PD. Longer reproductive lifespan resulting in higher "whole life" female sex steroids concentrations may exert a protective effect on central nervous system, resulting in milder course of the disease.