Catecholamines metabolism in thyroid diseases. I. Epinephrine secretion rate in hyperthyroidism and hypothyroidism

We have measured the secretion rate of epinephrine in 6 euthyroid, 6 hyperthyroid, and 6 hypothyroid subjects infused at a constant rate for a one hour period with tritiated epinephrine (.01 muc/kg/min) (New England Nuclear Inc.). Plasma and urinary levels of epinephrine were measured by modifying the fluorometric method of Anton and Sayre. Plasma levels of epinephrine were 3.0 +/- 3.0 ng/100 ml (mean +/- SD) in normal subjects, compared to 4.4 +/- 3.5 ng/100 ml (mean +/- SD) in hyperthyroid subjects. In urine, epinephrine values ranged from 1.3 mug/day to 6.1 mug/day in normal subjects. Mean value observed in hyperthyroidism was 4.9 +/- 2.6 mug/day and 3.8 +/- 1.0 mu/day in hypothyroidism. Plasma secretion rates averaged 48 +/- 27 mug/kg/day in normal subjects, compared to 54 +/- 18 mu/kg/day in hyperthyroidism and 43 +/- 20 mug/kg/day in hypothyroidism. Likewise, the mean urinary secretion rate was 55 +/- 27 mug/kg/day in normal subjects compared to 60 +/- 22 mug/kg/day in hyperthyroidism and 50 +/- 28 mug/kg/day in hypothyroidism. There is no statistical difference between the values found in the three groups of subjects (plasma and urine). Therefore, these results would indicate that the signs and symptoms encountered in hyperthyroidism are not secondary to a high secretion rate of epinephrine.