Endocrine Abstracts

Pituitary adenomas are in the majority of cases diagnosed by magnetic resonance imaging (MRI). In some cases, especially in functional tumors, there are too small adenomas for MRI resolution and we need other diagnostic modality (including petrosal sinus catheterization for laterality). Usefulness of positron emission tomography (PET) with fluorodeoxyglucose was demonstrated in some case report. In this case, we present 36 y/o women with no other comorbidities, which came at first in 2012 for 10 months persistent amenorrhea with normal gynecologic finding. Diagnosis of hyperprolactinemia was determined (PRL 2820 mIU/l = 132.5 ng/ml; 7 × ULN) and treatment with cabergoline (0.5 mg/weekly) was started. MRI revealed 4 mm microadenoma in right half of pituitary gland. Other pituitary function were normal. Until 6 months, PRL was normalized and cycle was restored. Next follow-up was lost. After five years, the patient came with the same problem – persistent amenorrhea with minor PRL elevation (1398 mIU/l), we started the same treatment with cabergoline. In contrary to previous course, no effect was observed, PRL increased regardless of the cabergoline dose (max 2 mg daily). Other pituitary functions remained normal. Switch to bromocriptine and next to quinagolide was not successful, maximal tolerated doses were completely inefficient and PRL was continuously increased (to 7038 mIU/l). MRI repeatedly (altogether 3 examinations in 1.5 year) with no pituitary pathology, originally founded microadenoma in right half of pituitary gland was disappeared. Macroprolactinemia was excluded. Therefore PET/MRI with FDG was performed, even with thought of ectopic prolactinoma. Surprisingly, we found thin (3 mm) strip of tissue around left carotid artery with sphenoid propagation (length 10 mm), with increased FDG uptake (SUV max 15). No other pathology was found. Neurosurgery cannot be radical in this case and then this locus was irradiated by gamma knife (35Gy on 46% isodose, Dmax 76Gy) with decreased PRL level to 1041 mIU/l after 3 months and 890 mIU/l after 6 months. MRI after 6 months showed regression of this “ectopic” prolactinoma to 4.5 mm length.

Conclusion: Treatment resistant hyperprolactinemia represents less than 5% of prolactinomas. Irradiation or neurosurgery are possible therapeutic modalities. Hybrid radiologic methods (PET FDG with MRI) can contribute to diagnosis in cases of ectopic or very small pituitary tumors.