Plasma prolactin response to L-dopa TRH and metaclopramide in thyrotoxicosis

The plasma PRL repsonse to synthetic TRH, L-dopa and metaclopramide was evaluated in patients with thyrotoxicosis. A PRL response similar to thtaclopramide,while no PRL response was observed after TRH. When the TRH-test was repeated after treatment, all patients showed a normal increment in plasma PRL. This data suggests that, in thyrotoxicosis, PRl response to TRH only is impaired, but PRL can be suppressed by L-dopa or released by metaclopramide notwithstanding the elevated values of thyroid hormone levels.