Effect of Different Dopaminergic Agents in the Treatment of Acromegaly

Medical treatment of acromegaly with dopamine agonists possesses 2 main advantages: the oral administration and the low costs. In this study, we reported on the results of chronic treatments with quinagolide (CV 205-502), cabergoline (CAB) and long-acting depot preparation of bromocriptine (BRC-LAR) in 34 acromegalics. Patients were divided into three groups on the basis of different treatment: CV 205-502 given to 16 patients at the dose of 0.3-0.6 mg/day for 6 months; CAB given to 11 patients at the dose of 1.0-2.0 mg weekly for 6 months; and BRC-LAR injected into 7 patients at the dose of 100 mg/month for 6-12 months. Basal and oral glucose tolerance test-stimulated serum GH levels, basal and TRH-stimulated PRL levels, plasma insulin-like growth factor I (IGF-I) levels, computed tomography scan, and/or magnetic resonance imaging were assessed before and quarterly during treatments. The chronic administration of CV 205-502, CAB, and BRC-LAR caused a significant decrease of circulating GH, IGF-I, and PRL levels (P < 0.005). Normalization of circulating GH and IGF-I levels was obtained in 7 of 16 (43.8%) patients treated with CV 205-502. Serum GH response to oral glucose tolerance test (oGTT) significantly improved (P < 0.005), and PRL levels were significantly suppressed during treatments. No correlation was found between basal and TRH-stimulated PRL levels and GH suppression during different therapies. Immunohistochemical staining revealed 19 GH-positive and 10 GH + PRL-positive adenomas. A significant association was found between GH/PRL staining and responsiveness to chronic treatments (chi 2 = 7.985, P < 0.005). Three patients had significant adenoma shrinkage. Slight nausea and hypotension which spontaneously disappeared within therapy progression, were referred by 5/16 patients during CV 205-502 and 2/7 during BRC-LAR. The results of this study indicate that CAB and BRC-LAR cannot be considered as useful medical approaches for acromegalics, whereas CV 205-502 normalized circulating GH and IGF-I levels in 47.8% of patients.