Summary The thermogenic response of brown adipocytes to glucagon was reduced by either thyroidectomy or adrenalectomy, while that to noradrenaline was not affected. Polyamines (spermine and spermidine) inhibited glucagon-induced thermogenesis of the cells. These results suggest that glucagon stimulates brown adipocytes under the influence of thyroidal and adrenal hormones, and that polyamines regulate the thermogenesis of brown adipocytes in an inhibitory way.