PRL and Brain atrophy: This approach was partly adopted in the recent deferiprone trial (Supplementary Table 1) where brain iron content using T2* sequences and plasma ferritin and prolactin levels were used as combined markers of target engagement and specific measures of treatment effect while structural imaging for measurement of brain atrophy and DAT-SPECT imaging was used to explore the impact of the agent on overall disease progression (atrophy and nigrostriatal degeneration).