TH and Parkinson disease: The higher susceptibility of men to sporadic Parkinson’s disease (sPD), may be a consequence of greater vulnerability to toxicants that affect the expression of Sry. In females, estrogen is also a player as injections of estradiol benzoate in rats increase TH mRNA (Serova et al., 2004) and ovariectomy results in loss of TH-positive neurons (Leranth et al., 2000).