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Pituitary Incidentalomas

Question:  We found a small tumor on my pituitary when performing an MRI because of another issue.  My doctor did some cortisol testing but most of my levels are normal and I don’t have symptoms of Cushing’s.  I found a lot of information online about harmless adrenal tumors and why a patient should have periodic testing to make sure they aren’t starting to cause problems, but I didn’t find anything similar about pituitary tumors.  Should I worry about this?

Answer 1:  I would not worry about it, but would consider getting a repeat MRI of the pituitary gland at some interval to be sure that the tumor is not increasing in size.  Your endocrinologist can help decide when this is done, based on the current size of the mass.  In general, we worry about two things with pituitary tumors:  whether they are functional (i.e. making hormones) and whether they are big enough to hurt nearby structures.  Unlike the adrenal gland tumors, non-functioning pituitary tumors almost always remain non-functioning.  In your case, if excess prolactin, growth hormone, alpha subunit, LH, and FSH have been excluded in addition to the normal Cushing’s workup, it’s very unlikely that the tumor will become hormonally active.  On the other hand, the size is important.  About 10% of healthy people have a non-functioning pituitary mass up to about 6mm in diameter.  These rarely enlarge. However, many physicians would re-check to be sure that a smaller mass is not growing, and if the mass is larger than 6mm, and definitely if it is more than 10 mm, repeat imaging is done to be sure that there is no growth. (Dr. Lynnette Nieman, NIH)

Answer 2:  The finding of an incidental small pituitary tumor (pituitary “incidentaloma”) on MRI is not rare.  Well-defined studies have shown the presence of small pituitary tumors at autopsy in 22.4% of randomly selected cases (Toronto) and 3% of randomly done MRI scans (Amsterdam).  At USC, we followed a group of 27 patients with microadenomas for 10 years during which time three of the tumors grew significantly.  Interestingly, all three were 6mm or greater in size when first discovered, and growth was observed within four years of initial discovery.  Although the vast majority of microadenomas do not grow, obviously some do or we would not see macroadenomas.  Therefore, a patient with an incidentally found non-functional microadenoma should be followed by repeat scanning.  Our protocol is to follow patients with MRI scans annually for five years.  If no growth in that period, we get another scan at seven years and one final scan at 10 years.  If no growth by 10 years, we do not get additional scans.  The 10 year scan may be somewhat excessive, but we tend to err on the conservative side in that respect.  (Dr. Martin Weiss, University of Southern California)

Answer 3:  Adenomas do not change in characteristics, in other words if they are non-functioning they remain non-functioning. Conversely, some adrenal tumors can produce more cortisol with time. If your doctor has completely ruled out Cushing’s with at least two different kinds of tests (two 24 hour urine, bedtime saliva, and dexamethasone suppression test) there is no need to repeat the Cushing work up. (Dr. Roberto Salvatori, Johns Hopkins Pituitary Center)

Answer 4:  The words I’m picking up here – “some cortisol testing and most levels are normal” – would make me recommend a full workup either now or in some months from now to further look into mild Cushing that would declare with time vs nothing to worry about (2-3 midnight salivary cortisol, 24h urine cortisol, low dose Dexamethasone test with Dex level).

Up to 10-15% of the adrenal adenomas can start secreting cortisol later on and this is not generally the case with nonfunctional pituitary tumors if appropriately labeled so.  On the other hand, I had a patient with normal IGF1 for years and known pituitary tumors who started to have progressive elevation in IGF1 and later confirmed to have GH producing tumor after surgery … so I now add an IGF1 along with the MRI for monitoring.  (Dr. Georgiana Dobri, Cornell)

(Winter-Spring 2019)

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