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.