Plasma beta-lipotropin levels in Parkinson's disease

Previous reports have indicated that patients with Parkinson's disease have elevated plasma levels of immunoreactive (IR) beta-melanocyte stimulating hormone (beta-MSH), which may have implications as to its pathogenesis and treatment. Recent methodological advances, however, have demonstrated that what had originally been measured in human plasma as beta-MSH actually represents beta-lipotropin (beta-LPH), and that beta-MSH as such does not normally circulate in human plasma. With the capacity to specifically measure immunoreactive beta-LPH in human plasma, we have determined plasma levels of immunoreactive beta-LPH as well as ACTH and prolactin in three groups of subjects: A. Parkinson patients untreated with levodopa (n = 11); B. Parkinson patients on levodopa therapy (n = 21); C. Controls (n = 6). No difference was found in plasma levels of IR-beta-LPH and IR-ACTH between these three groups. Plasma levels of prolactin were not different in either group of Parkinsonian patients as compared to controls. However, prolactin levels were significantly lower in the Parkinsonian patients treated with levodopa versus the untreated group. These data suggest that there is no defect in beta-LPH release from the pituitary in Parkinson's disease.