Homogeneity in the Growth Hormone–Lowering Effect of Dopamine and Somatostatin in Acromegaly*

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Abstract
The effect of maximally inhibiting doses of dopamine (DA) or somatostatin on GH [growth hormone] levels was studied in 39 acromegalic patients. The GH-lowering effects of the 2 drugs were highly variable in different patients. A significant correlation (r = 0.45; P < 0.01) was found between the percent changes obtained during the infusions of DA (500 .mu.g/min) and somatostatin (3.33 .mu.g/min). Pretreatment with L-sulpiride markedly blunted the inhibitory effect of DA, but did not affect the response to somatostatin. The GH-secreting cells of acromegalic patients apparently contain separage receptors for DA and somatostatin. The partial or total lack of responsiveness to DA or somatostatin may be due to the loss of receptors for these agents on the GH-secreting neoplastic cells.