Plasma β-lipotropin in the human

To date there has been no specific immunoassay for human lipotropin (LPH). The importance of such an assay is evident with the realization that [β-LPH, not β-MSH, is present in human pituitary and plasma. There is no evidence for the presence of a human s-MSH. This has been shown to be a breakdown product derived by cleavage from β-LPH during in vitro extraction procedures. Previous reports of the measurement of human LPH have relied on indirect evidence obtained from data derived by RIA for ‘βh-MSH’. These assays have utilized antibodies, raised either against ACTH or β-MSH. In some of these reports, but not all, it has been demonstrated that such antibodies partially or completely cross-react with β-LPH or γ-LPH and react with a material in plasma which has an elution pattern on gel filtration identical or closely related to that of the lipotropins. The studies to be reported are based on the development of a homologous RIA for human LPH which has no cross-reactivity with β-MSH. Data will be presented on the measurement of basal and stimulated plasma LPH concentrations in normal subjects, and in patients with abnormalities in ACTH and cortisol secretion, and correlation of these concentrations with those of plasma ACTH.