title: Regulation of prolactin secretion in patients with Cushing's disease. A comparative study on the effects of dexamethasone, lysine vasopressin and ACTH on prolactin secretion by the rat pituitary gland in vitro.
abstract: In 15 untreated patients with Cushing's disease the regulation of prolactin (PRL) was evaluated. Plasma PRL was 11.5 +/- 4.8 vs. 5.3 +/- 3.6 ng/ml (patients with Cushing's disease vs. control; mean +/- S.D.; p less than 0.001). The maximal increment of plasma PRL in response to TRH was 32.3 +/- 17.3 vs. 27.9 +/- 17.2 ng/ml (NS); the maximal increment of plasma PRL in response to an insulin-induced hypoglycemia was 3.8 +/- 4.6 vs. 22.7 +/- 12.4 ng/ml (p less than 0.001). Additionally the effect of dexamethasone, lysine vasopressin and ACTH on the secretion of PRL by rat pituitary glands in vitro was studied. Dexamethasone (1.25--10 microM) inhibited the secretion of PRL. However, in the presence of dexamethasone modulation of PRL release by TRH and dopamine remained unaltered. Lysine vasopressin (5 nM - 5 microM) and ACTH (0.5--12.5 microM) did not have a direct effect on PRL release by normal rat pituitary glands in vitro and these substances also did not interfere with dopamine-mediated inhibition of PRL release.
  
  
  CONCLUSIONS
  In Cushing's disease the PRL responses to TRH (normal) and to insulin-induced hypoglycemia (blunted) are differentially affected. Therefore, hypercortisolism probably selectively interferes with the regulation of PRL secretion at a suprahypophyseal level. It is concluded that TRH and dopamine regulate PRL release at sites which are not under corticosteroid regulation, while corticosteroids modulate PRL secretion in response to stress.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000328:Adult; D000818:Animals; D003480:Cushing Syndrome / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D008236:Lypressin / Q000494:pharmacology; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D008875:Middle Aged; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000502:physiology
chemical_list: D007328:Insulin; D008236:Lypressin; D013973:Thyrotropin-Releasing Hormone; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D004298:Dopamine; D008797:Metyrapone