The pituitary in nuclear medicine imaging.

The pituitary is an endocrine gland with ability to uptake diverse radiopharmaceuticals and, therefore, susceptible to be investigated by nuclear medicine diagnostic procedures. Although this topic has been scarcely scrutinized, we have data indicating that somatostatin receptor scintigraphy with111In-DTPA-D-Phe-octreotide or 99mTc-EDDA/HYNIC-TOC may be of clinical utility in the diagnosis of some pituitary adenomas (PA). Only a few studies have evaluated the diagnostic performance of 99mTc-MIBI and 99mTc (V)-DMSA scintigraphy in pituitary disease. Scintigraphy using 123I-methoxybenzamide (123I-IBZM) might be useful in macroprolactinomas expressing dopamine D2 receptors. Pituitary gland does not usually accumulate 2-deoxy-2-[18F]fluoro-d-glucose (18F-FDG) and, therefore, it is not visualized on positron emission tomography (PET) imaging studies with this radiotracer. The pituitary uptake on18F-FDG PET/CT scans performed in the follow-up of oncological patients are uncommon. However, 60% of these incidental findings are due to PA, mainly non-functioning pituitary macroadenomas, and a small percentage to metastases or other pituitary lesions. Interestingly, 18F-FDG PET/CT may identify hypophysitis induced by different immunotherapeutic agents used in cancer patients. Positive 18F-FDG uptake has been reported in a high percentage of patients with PA, mainly macroadenomas and it seems that there is correlation between tumor size and SUVmax. 68Ga-DOTA-TATE PET/CT may identify functioning and non-functioning PA, although this technique is more useful in the detection of remaining normal pituitary tissue after transsphenoidal adenomectomy, and in the confirmation of recurrence of functioning PA, such as thyrotroph-secreting PA. Furthermore, 68Ga-DOTA-TATE uptake has potential therapeutic implications on molecular-targeted therapy. Lastly, other radiopharmaceuticals that have shown to be taken up in some patients with pituitary disease include 18F-DOPA (prolactinoma), 11C-methionine (residual or recurrent PA), O-(2-18F-fluoroethyl)-l-tyrosine (metastasis), 18F-choline (silent adenoma, ectopic corticotropinoma), and 13N-ammonia (hypopituitarism).