Dynamic testing of prolactin and growth hormone secretion in patiens with neuroendocrine disorders

Abstract

Abstract. Prolactin (Prl) and growth hormone (GH) responses to different pharmacologic probes acting at the central nervous system (CNS) or the anterior pituitary (AP) level were evaluated in patients with distinct neuroendocrine disorders. Thirteen patients with Prl-secreting tumours (PST), 10 acromegalics (A) and 8 patients with hypothalamic lesions (HL), as assessed on clinical, radiological and surgical grounds, underwent on separate occasions acute testing with the opioid peptide FK 33-824 (0.5 mg iv), the indirect dopamine (DA) agonist nomifensine (NOM, 200 mg po), the DA receptor antagonist domperidone (DOM, 10 mg iv), TRH (200 μg iv) and insulin (ITT, 0.10-0.15 IU/kg iv). All patients were evaluated pre-surgery and 4 of them also post-surgery. Prl and GH were evaluated by RIA at different time intervals following treatments. Peculiar features of Prl and GH response could be evidenced in the patients as follows: Prl: PST patients did not respond either to stimulation by FK 33-824 (12/13) or to inhibition by NOM, (9/10), but 2/8 and 4/12 of them did respond to DOM or TRH stimulation, respectively; 8/10 A and all of the HL patients did not suppress plasma Prl following NOM, but many of them did respond to FK 33-824 (6/10 A, 5/8 HL) and TRH (9/10 A, 6/8 HL); as for GH, PST patients could be divided into FK 33-824 responders (8/12) and non-responders, whereas in only one of the A and in none of the HL patients a consistent response to the peptide was present; a major difference between A and HL patients was the ability of TRH to elicit a GH rise in the former (8/10) but not the latter (0/6). In conclusion, concomitant application of different CNS- or AP-acting stimuli seems to enable better functional connotation of individual disorders, and hence, provide information of value for the underlying pathophysiology.