Estrogen may have neuroprotective effects by reducing the dopaminergic neuron depletion caused by neurotoxins in the PD animal study.41 A recent study showed a greater susceptibility to PD in men with lower sex hormone and higher serum prolactin level.42 Thus, it may be possible that sex hormone plays a role in inducing or worsening PD, though studies of testosterone treatment in men suffering from PD show equivocal results.43,44. Here, PRL is linked to Parkinson disease.