Clinical evaluation of a radioimmunoassay for β-MSH-related peptides (lipotrophins) in human plasma

A radioimmunoassay for β-MSH related peptides ('β-MSH') which measured βh- and γh-lipotrophin (LPH) and β-MSH, was used to assess LPH status and the stability of 'β-MSH' in blood and plasma. 'β-MSH' concentrations correlated well with ACTH levels in paired snap-frozen plasma samples from normal subjects, from patients with pathologically elevated hormone levels (except those with chronic renal failure), and during acute stimulation and suppression tests. It is concluded that the 'β-MSH' assay provides at least as good discrimination as the ACTH assay in situations in which the latter is diagnostically valuable. Determination of the ratio of 'β-MSH' to ACTH levels may help to distinguish between untreated Cushing's disease and the ectopic ACTH syndrome. The stability of 'β-MSH' immunoactivity allows unhaemolysed blood and plasma samples to be transported at ambient temperature without loss of diagnostic value. (author)