Regulation of lipolysis in hyperthyroidism.
The investigation (Fig. 1) clearly shows that the ability of isoprenaline in particular and, to a less extent, of noradrenaline to increase the accumulation of cyclic AMP and thus also the rate of lipolysis is enhanced in hyperthyroidism. No evidence was found of changes in the sensitivity to either beta 1- or alpha -adrenergic agonists. Although further studies are needed, the findings supported the idea that the augmented cyclic AMP accumulation is due to changes below the receptor level. Second, a significant decrease was observed in the apparent Vmax of the PDE with apparent low Km. Third, metabolic disturbances closer to the lipolytic system may exist. Some indirect evidence for this hypothesis was the finding of relatively more rapid lipolysis in relation to the cyclic AMP level in hyperthyroidism. The investigations have raised a number of questions about the nature of the metabolic changes in hyperthyroidism. The findings suggest that there are multiple abnormalities, localized at different levels of mechanisms regulating lipid mobilization. Investigations of subcutaneous tissue fragments in man seem to offer good opportunities for exploring these abnormalities.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D006801:Humans; D006980:Hyperthyroidism / Q000378:metabolism*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008066:Lipolysis / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D000242:Cyclic AMP; D007545:Isoproterenol