Diagnostic imaging of dopamine receptors in pituitary adenomas

Dopamine D2 receptor scintigraphy of pituitary adenomas is feasible by single-photon emission computed tomography using 123I-S-(−)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-hydroxy-3-iodo-6-methoxybenzamide (123I-IBZM) and 123I-epidepride. 123I-epidepride is generally superior to 123I-IBZM for the visualization of D2 receptors on pituitary macroadenomas. However, 123I-IBZM and 123I-epidepride scintigraphy are generally not useful to predict the response to dopaminergic treatment in pituitary tumour patients. These techniques might allow discrimination of non-functioning pituitary macroadenomas from other non-tumour pathologies in the sellar region. Dopamine D2 receptors on pituitary tumours can also be studied using positron emission tomography with 11C-N-raclopride and 11C-N-methylspiperone.