In 1972 L-dopa was first found to cause a paradoxical suppression of GH in many patients with acromegaly; bromocriptine, a long-acting dopamine agonist, also has this property. These effects are antagonised by haloperidol, pimozide and metoclopramide which are specific dopamine antagonists. The hypothalamic hormone, somatostatin, also decreases GH secretion in acromegaly. Unfortunately, its short half-life means that its effects wear off after a few minutes.
Recently, long-acting analogues of somatostatin (e.g. octreotide) have become available for use in the treatment of acromegaly. Thyrotrophin releasing hormone (TRH) and gonadotrophin releasing hormone (GnRH) may also cause GH secretion in many acromegalic patients, twenty and thirty per cent respectively, but not in normal subjects.
