THE EFFECT OF METOCLOPRAMIDE, TRH AND L-DOPA ON PROLACTIN SECRETION IN PITUITARY ADENOMA AND IN "FUNCTIONAL" GALACTORRHOEA SYNDROME

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Abstract
The degree of autonomy in prolactin secreting pituitary adenomas and also prolactin secretory reserve in cases with suspected functional galactorrhea syndrome was evaluated with the use of metoclopramide, TRH and L-dopa. In patients with pituitary adenoma the basal prolactin (PRL) level often exceeded 150 .mu.g/l and the response to stimulation with TRH and/or metoclopramide was markedly diminished or even nonexistent, while the response to L-dopa was usually retained. In patients with galactorrhea and/or amenorrhea with normal skull X-ray the basal PRL level was either normal or moderately raised. The response to stimulation varied, being often excessive, sometimes normal and in some other cases markedly diminished (as in patients with adenoma). The "functional disorder" of prolactin secretion is mainly hyperresponsiveness to stimulation, whereas the basal PRL level in those cases is usually normal or only intermittently raised. In cases with a moderate hyperprolactinemia, especially if it appears to be constant, and the response to stimulation is diminished or none at all, a pituitary microadenoma is suspected. There are rare cases of galactorrhea with normal basal PRL and normal response to stimulation, in which the sensitivity of the mammary PRL receptor is probably increased. The above mentioned PRL stimulation tests may help in distinguishing between tumoral and functional hyperprolactinemia.