Evaluation of hypothalamic dopaminergic function in patients with pituitary prolactinoma.

This study was carried out using a dopaminergic agonist (carbidopa plus levodopa, CD + LD) and antagonist (metoclopramide, MCP) respectively for dynamic tests to observe the variations of serum prolactin (PRL), thyrotropin (TSH) and luteinizing hormone (LH) levels in 7 normal women and 11 women with pituitary prolactinoma. It was shown that CD + LD resulted in minimal suppression of serum PRL (18.4 +/- 3.4%) in tumor patients, with this being significantly less than that in normal women (80.7 +/- 4.6%). However, similar degrees of TSH and LH suppression were observed after CD + LD in patients (23.8 +/- 4.2% and 28.2 +/- 2.1%, respectively) and in normal women (27.9 +/- 2.4% and 34.7 +/- 9.0%, respectively). MCP greatly increased PRL levels in the normal women as compared with the patients (892.1 +/- 195.3%, 16.4 +/- 6.5%), but increased TSH and LH levels were much higher in the patients than in the normal women (291.4 +/- 36.1% vs 19.9 +/- 3.3% and 96.9 +/- 7.4% vs 24.9 +/- 5.5%, respectively). It was also found that the levels of TSH or LH after MCP strongly correlated with basal PRL levels in the patients (r = 0.858, P less than 0.001 and r = 0.737, P less than 0.01, respectively). These results indicate that synthesis, turnover and release of hypothalamic dopamine are normal and the hypothalamic tone is relatively high in patients with PRL-secreting pituitary tumors.