Plasma dopamine-beta-hydroxylase activity and thyroid suppressibility in Graves' disease

Plasma dopamine-beta-hydroxylase (DBH) activity, serum T4, T3, T3U, and the 24-hr thyroid uptake before triiodothyronine suppression testing were studied in 34 patients with treated Graves' disease. Although all of them were in the euthyroid state, there was a statistically significant difference in presuppression plasma DBH activity between those patients who showed suppression of their RAI uptake with triidothyronine and those who did not. This suggests a relationship between plasma DBH activity and thyroid suppressibility.