Biochemical acromegaly in patients with prolactinoma during treatment with dopaminergic agonists

OBJECTIVE: To evaluate the frequency of subclinical acromegaly (in the absence of clinical phenotype but biochemically uncontrolled) in patients with prolactinoma during treatment with dopaminergic agonists. SUBJECTS AND METHODS: One hundred twenty one patients without a phenotype suggestive of acromegaly were studied. RESULTS: Initially, the laboratory diagnosis of acromegaly was unequivocal (elevated IGF-1 for gender and age with nadir GH > 1 μg/L) in two patients, and likely (elevated IGF-1 with nadir GH > cut-off but < 1 μg/L) in another patient. In two other patients, this diagnosis was possible (normal IGF-1 with nadir GH > 1 μg/L). Repetition of the tests 6 months after withdrawal of the dopaminergic agonist confirmed the diagnosis of subclinical acromegaly (elevated IGF-1 for gender and age with nadir GH > 1 μg/L) in these 5 patients. False-positive results were excluded in all cases. CONCLUSION: In patients with prolactinomas, acromegaly should be investigated not only in cases with a clinical phenotype.