Catecholaminergic interactions in the regulation of thyrotropin (TSH) secretion in man.

The TSH responses to the catecholamine depleting agent monoiodotyrosine (1 g po) and the dopamine receptor blocking drug metoclopramide (10 mg po) have been compared in euthyroid and hypothyroid subjects. Both drugs lead to a prompt and significant rise in TSH levels (peak values at 60-75 min) which is very much greater in hypothyroid than euthyroid subjects. The findings lend further support to the inhibitory role of dopamine in the control of TSH release in man, since TSH release follows either dopamine depletion with monoiodotyrosine or dopamine receptor blockade with metoclopramide.