Metabolism of Catecholamines in Hyper- and Hypo-thyroid Patients

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Abstract
In patients with hyperthyroidism, the sensitivity to infused noradrenaline was distinctly increased. On hypothyroid patient reacted normally to the infusion. Both hyper- and hypothyroid patients excreted comparable amounts of adrenaline, noradrenaline, metadrenaline, normetadrenaline and vanillylmandelic acid (VMA) to normal controls. It may be concluded that the endogenous production of catecholamines is normal in thyroid patients. Basal metabolic rate, protein bound iodine, uptake of I131, systolic and diastolic blood pressure, pulse pressure, and pulse rate were all in no correlation with either urinary adrenaline or noradrenaline in thyroid patients. The ratio urinary catecholamines/ methoxy catecholamines/VMA was within normal range in thyroid patients. The ratio calculated in the urine obtained after noradrenaline infusion was not significantly different in thyroid patients from that in healthy controls under similar experimental condition. This may be interpreted as indicating no enzymatical abnormality in monoamine oxidase and catechol O-methyl transferase. Recovery of infused noradrenaline in urine excreted for 24 hours after its infusion was 2.9-3.3 per cent in patients with hyperthyroidism as in normal controls. In the experiment of noradrenaline infusion, the urinary excretion of the amine was highest during infusion, then decreased rapidly to pre-infusion level in two hours, whereas the excretion of its metabolites, normetadrenaline and VMA, remained at higher level for several hours after the infusion. The excretion pattern did not significantly differ in the two groups, hyperthyroid patients and normal controls. The increase in the excretion of adrenaline and metadrenaline during noradrenaline infusion was greater in hyperthyroid patients than in controls. A marked increase in the excretion of methoxy catecholamines and distinct decrease in urinary VMA were observed in healthy subjects receiving JB-516, a potent monoamine oxidase inhibitor.