Evaluation of two inhibitory tests (nomifensine and L-dopa + carbidopa) for the diagnosis of hyperprolactinaemic states.

It has been reported that administration of nomifensine (Nom) or of L-dopa + carbidopa (L-dopa + Carb) potentiates central dopaminergic tonus, resulting in decreased prolactin (PRL) secretion. It has been proposed that these drugs would help to discriminate patients with PRL-secreting pituitary tumours from those with so-called 'functional' hyperprolactinaemia. In this study, oral Nom (200 mg) was given to forty-three hyperprolactinaemic patients and L-dopa + Carb (50 mg Carb every 6 h for four doses followed by L-dopa 100 mg and Carb 35 mg) to thirty of them and both treatment to ten normal subjects. The hyperprolactinaemic patients were divided into four clinical groups. Group A, twenty patients with proven PRL-secreting pituitary tumours; Group B, thirteen women with elevated PRL levels (less than 100 ng/ml) without any radiological evidence of a pituitary tumour (hyperprolactinaemia of unknown aetiology or 'functional' hyperprolactinaemia); Group C, four women with polycystic ovarian disease and mildly elevated serum PRL; Group D, six patients with various other disorders associated with hyperprolactinaemia. PRL levels decreased in the normal controls below the basal values by 61.3% +/- 6.2 (SEM) after Nom and 77.6% +/- 4.2 after L-dopa + Carb. Decreases in serum PRL of at least 50% (in three consecutive determinations) were found in group A in 20% of patients after Nom and in 25% after L-dopa + Carb; in group B in 15% and 40% of cases; in most of the hyperprolactinaemic women in group C; and some in group D. In conclusion, these two treatments did not discriminate between tumorous and non-tumorous cases of PRL hypersecretion.