Tuberoinfundibular dopaminergic function in Parkinson's disease.

A deficit of nigrostriatal, mesocortical and mesolimbic dopamine systems in Parkinson's disease is well known. We know less about the involvement of tuberoinfundibular dopamine (TID) systems. In untreated (naive or wash-out) men with Parkinson's disease, we studied TID function through basal and stimulated plasma levels of growth hormone, prolactin and thyrotropin. Only minor abnormalities in prolactin responses to thyrotropin-releasing hormone were found, probably reflecting denervation hypersensitivity. TID function is preserved in men with Parkinson's disease.