The value of an intravenous TRH test for the diagnosis of tumoural prolactinaemia.

The plasma Prl response to 200 micrograms TRH iv was evaluated in 6 hyperprolactinaemic women without radiological evidence of a pituitary tumour (group I), in 15 hyperprolactinaemic women with dubious (group II) and in 17 normo- or hyperprolactinaemic women with clear (group III) radiological abnormalities, in 18 normo- or hyperprolactinaemic men with clear radiological abnormalities (group IV), and in 4 women and 3 men with hyperprolactinaemia and sellar destruction who had been treated in the past for pituitary adenoma (group V). The responses were compared with those obtained in a control group of 83 (42 women, 41 men) normoprolactinaemic healthy individuals. The Prl response was defined as a ratio (R2): the 20 min value minus the 0 min value, divided by the 0 min value. The median R2 values were: female controls 5.1, male controls 3.1, group I 0.1, group II 0.2, group III 0.3, group IV 0.55, group V females 0.45 and males 0. It is concluded that 1) subjects suspected of harbouring a microprolactinoma (groups I and II) demonstrate absent or attenuated responses similar to those found in patients with definite prolactinomas and 2) a value of plasma Prl 20 min after 200 micrograms TRH iv greater than 3.5 times the basal level (R2 > 2.5) rules out the presence of a prolactinoma.