We have studied the response of prolactin (PRL) secretion to the test combining i.m. sulpiride in the dose 1 mg/kg followed by 200 micrograms i.v. of TRH, in 12 normal women and 37 patients with hyperprolactinaemia. The response was expressed as a percentage rise in plasma PRL concentration (delta %) 20 minutes after the administration of sulpiride or TRH. In the controls the response in PRL secretion to sulpiride worked out at between 639 and 2,760%. When there was a pituitary adenoma or supra-sellar lesion the PRL response to sulpiride was always less than 481%. On the other hand the PRL response with TRH after sulpiride was not significantly different as between the controls (less than 175%) and the patients (less than 91%). We conclude: 1) the combined sulpiride and TRH test is useless for assessing hyperprolactinaemia; 2) the sulpiride test on the other hand makes it possible to show that hyperprolactinaemia cannot be stimulated and to suspect the presence in this case of a prolactin producing adenoma or a supra-sellar tumour.
