[Effect of acute levodopa load on blood prolactin concentration in patients with thyroid diseases]

In 14 thyrotoxic patients and 5 persons with endemic euthyroid goiter the blood plasma prolactin content was studied under the action of an acute oral load of levodopa in a dose of 0.5 g. It was found that the basal prolactin level was significantly higher in the blood of patients of both sexes with thyrotoxicosis and endemic euthyroid goiter than that in the control group (10 healthy humans). The blood plasma prolactin content markedly decreased in thyrotoxic patients under levodopa effect, regardless of the sex, whereas in patients with endemic euthyroid goiter the drug exhibited no considerable action on the prolactin level. A possible mechanism of hyperprolactinemia in the thyroid hyperfunction is discussed.