No acute effect of pimozide on the plasma GH levels in acromegaly.
In 34 acromegalic patients either untreated or inadequately treated by surgery and/or radiotherapy the plasma GH levels and plasma Prl levels were determined during 8 h after the acute administration of the dopamine agonist bromocriptine and during 150 min after the administration of the dopamine antagonist pimozide. A 50% or more suppression of the basal GH levels was arbitrarily defined as a positive response. Seventeen patients displayed a positive response to bromocriptine, 17 patients displayed a negative response to bromocriptine. Plasma Prl levels were elevated in 6 of 17 bromocriptine responders and in 2 of 17 bromocriptine nonresponders. There was no difference in the plasma GH response to pimozide administration in the patients with a positive or a negative GH response to bromocriptine. With one exception there was in no patient a positive GH response to pimozide. In further experiments the plasma GH response to pimozide was measured during 11 h in 6 bromocriptine sensitive and 6 bromocriptine insensitive patients. Again no difference was found between bromocriptine responders and non-responders. There was also no difference in the Prl response to bromocriptine or pimozide between GH responders and GH non-responders. The Prl response to pimozide was blunted in comparison to a control group. The present study does not not lend support to the idea that there is a fundamental difference in the degree of hypothalamic dopaminergic control of GH or Prl secretion between bromocriptine sensitive and bromocriptine insensitive patients with acromegaly.
D000172:Acromegaly / Q000097:blood* / Q000188:drug therapy; D000328:Adult; D000368:Aged; D001971:Bromocriptine / Q000494:pharmacology; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010868:Pimozide / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood; D011954:Receptors, Dopamine / Q000187:drug effects
D011954:Receptors, Dopamine; D010868:Pimozide; D001971:Bromocriptine; D011388:Prolactin; D013006:Growth Hormone