PARADOXICAL RESPONSE OF GROWTH-HORMONE TO PEPTIDE HISTIDINE METHIONINE IN ACROMEGALY - COMPARISON WITH THE EFFECTS OF THYROTROPIN-RELEASING-HORMONE AND VASOACTIVE-INTESTINAL-PEPTIDE

We examined whether peptide histidine methionine (PHM) induces a paradoxical rise in plasma GH in patients with acromegaly. PHM (100-mu-g) was given as an iv bolus to eight patients with active acromegaly, and plasma GH levels were measured before and at intervals up to 120 min after the injection. For comparison, the effects of TRH (500-mu-g) and vasoactive intestinal peptide (VIP, 100-mu-g), peptides known to paradoxically stimulate GH secretion in acromegalics, were assessed in all of the patients. A paradoxical rise (> 50% above the basal) in plasma GH was observed in five patients after both TRH and VIP administrations, although TRH responders were not always VIP responders, nor did VIP responders always respond to TRH. In two patients, the GH response to PHM fulfilled the criteria of a paradoxical increase. Both of these patients were also TRH and VIP responders. These results suggest that PHM may be another hypothalamic hormone capable of paradoxically stimulating GH secretion in at least some acromegalics, although PHM appears to be a less potent stimulator of GH release than TRH and VIP. The pathophysiological significance of this phenomenon is yet to be determined.