Abstract
Less than 1% of cases of acromegaly are secondary to ectopic secretion of Growth Hormone Releasing Hormone (GHRH), usually from a neuroendocrine tumor. Symptoms of ectopic acromegaly did not differ from classical acromegaly from pituitary origin. GH and IGF 1 values are in the same range. GHRH measurement only could make the correct diagnosis but is not routinely proposed in acromegaly. MRI of the pituitary gland is considered not very effective in ectopic acromegaly. In the literature (1), different patterns are described: pituitary enlargement (46%), adenoma (30%), empty sella (2%) or normal (20%). But T2MRI signal of the pituitary is never mentioned nor illustrated. Finally, in about 30 % of published cases, pituitary surgery, of course inefficient, was performed.
These data enhance the poor contribution of imaging studies in the published cases of ectopic acromegaly.
We have been able to obtain and read MRIs and particularly T2WI of 27 acromegalic patients- 20 female, 7 male- due to GHRH hypersecretion from a neuroendocrine tumor –principally bronchial carcinoid and pancreatic NET- which have been published or not. Remarquably, T2 sequences were available in only 27/61 cases we have collected. In all these 27 cases but two, the T2 signal was clearly hypointense if compared with the brain cortex, as it has been described in densely granulomated somatotropinomas (2). In one case with T2 hyperintensity, the pituitary mass presented the same imaging characters as multiple brain metastases from a bronchial carcinoïd. In one case, T2 signal was isointense. In 3 cases, tiny millimetric T2 hyperintense images were disseminated within pituitary hyperplasia. In several cases where pituitary MRI was considered as normal, correlation of the patient’age with pituitary size could make suspect an enlarged gland. In a case labeled empty sella, T2MRI signal of the pituitary remnant was hypointense. When coupling T2 and T1 gadolinium enhanced sequences, no pituitary adenoma was visualized and normal pituitary tissue was never identified along with pituitary hyperplasia.
In conclusion, T2 MRI hypointense signal of the pituitary gland is a better hallmark than pituitary hyperplasia for the diagnosis of acromegaly due to
GHRH ectopic secretion. Analysis of T2 MR signal in these cases is essential to avoid unnecessary interventions to the pituitary.
References
1 Ghazi A Endocrine 2013
2 Potorac J Endocr Relat Cancer 2015
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