RESUMO
1. The possible correlation between secretions of adrenocorticotropic hormone (ACTH) and of ß-lipotropin (ß-LPH), two pro-opiomelanocortin (POMC)-derived peptides, was investogated in 27 normal subjects under basal conditions (circadian rhythmz0, after the administration of 1 mg dexamethasone and in tests involving acute (human corticotropin releasing hormone, hCRG, and insulin tolerance test, ITT) and chronic (metyrapone) simulation. 2. All subjects presented circadian rhythm and an operating negative feedback mechanism. Plasma ACTH and ß-LPH concnetrations were correlated in al tests. The increase in ACTH and ß-LPH levels after hCRH was lower than that detected after ITT, though both increases were more discrete than those detected after stimulation with metyrapone. 3. The data suggest that, under hypoglycemic conditions, ACTH and ß-LPH secretion involves other POMC secretagogues in addition to endogenous CRH. The batyre of these factore remains undefined. The greater efficacy of metyrapone treatment in elevating ACTH and ß-LPH levels is most likely mediated by sustained reduction in cortisol production and interrruption of the rapid steroid feedback on the pituitary. The molar peak ratios of the acute tests, vere similar to one another, differed from the peak ratio obtained during the metyrapone test, suggesting that corticotrophs may present polls with differentiated ACTH and ß-LPH content and release according to the type and/or duration of the stimulus
