Normal and abnormal regulation of β-MSH in man

The regulation of plasma β-melanocyte-stimulating hormone (β-MSH) in man has been studied utilizing a radioimmunoassay previously described (1). In normal subjects plasma β-MSH values ranged from 20 to 110 pg/ml. Metyrapone increased and dexamethasone decreased plasma β-MSH levels. Surgical stress stimulated β-MSH secretion. Plasma β-MSH levels were elevated in patients with untreated Addison's disease and untreated congenital adrenal hyperplasia, and these levels fell to normal during glucocorticoid therapy. In patients with Cushing's syndrome due to pituitary adrenocorticotropic hormone (ACTH) excess, plasma β-MSH was slightly elevated before treatment. In those patients who developed pituitary tumors and hyperpigmentation after bilateral adrenalectomy, plasma β-MSH was greatly elevated. In patients with Cushing's syndrome due to adrenal tumor, plasma β-MSH was subnormal. In patients with the ectopic ACTH syndrome, the levels of plasma β-MSH were high. Plasma β-MSH had a diurnal variation in normal subjects, patients with Addison's disease, and patients with congenital adrenal hyperplasia; but the normal diurnal variation was lost in patients with Cushing's disease. In patients with high plasma β-MSH, simultaneous determinations of plasma ACTH showed close correlation between the degree of elevation of ACTH and that of β-MSH. In extracts of tumors from patients with the ectopic ACTH-MSH syndrome the quantities of the two hormones were roughly equivalent. In patients with hyperpigmentation due to a variety of disorders other than pituitary-adrenal abnormalities, plasma β-MSH was normal. It is concluded that the secretion of β-MSH is regulated by the same factors that regulate ACTH.

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