SFEBES2016 Poster Presentations Neuroendocrinology and pituitary (34 abstracts)
MicroTSHoma: an emerging clinical entity with ‘atypical’ biochemical features and often ‘normal’ imaging characteristics on MRI
Olympia Koulouri 1, , Carla Moran 1, , Sarah Heard 2 , Greta Lyons 1, , Rob Smith 1 , Franklin Aigbirhio 1 , Nagui Antoun 2 , Heok Cheow 2 , David Halsall 2 , Krish Chatterjee 1, & Mark Gurnell 1,
1University of Cambridge, Cambridge, UK; 2Addenbrooke’s Hospital, Cambridge, UK.
Background: Heightened awareness, as well as frequent thyroid function testing, have contributed to a recent rise in the incidence of thyrotropinomas. Microadenomas are now increasingly being recognized. The classical textbook description of thyrotropinomas is based on historically reported features in patients who typically had large/invasive lesions. The phenotype of microTSHomas could therefore differ.
Methods: We reviewed the records of all TSHomas referred to our centre in the last 5 years. Investigations in all patients included TFTs, alpha-subunit (ASU) and ASU:TSH molar ratio, SHBG, TRH stimulation testing and pituitary MRI. A subgroup of these patients additionally underwent detailed metabolic/physiological studies including measurement of resting energy expenditure (REE), sleeping heart rate (SHR), DXA and pituitary imaging with SPGR MRI and 11C-Methionine PET/CT.
Results: Forty-three prospective cases were identified, 22 of which were microTSHomas (51%). ASU was normal in 70% of microTSHomas and was significantly lower than in the macro cases (1.9 IU/l vs 4.8 IU/l, P=0.04). SHBG was not elevated in one third of cases. Response to TRH stimulation was more pronounced in micro- compared to macroTSHomas (1.97- vs 1.17-fold rise, P=0.0075), but remained ‘flat’ in both groups. Pituitary MRI was reported as normal or inconclusive in 51% of cases. Detailed imaging with SPGR MRI and 11C-Methionine PET/CT identified the culprit lesion in 9/13 (69%) cases with ‘negative’ MRI. Although many patients were relatively asymptomatic, they had raised REE and SHR and low BMD.
Conclusion: Despite, in many cases, very few overt symptoms, patients with microTSHoma demonstrate sequelae of thyrotoxicosis. Traditional tests employed in the diagnosis of TSHoma can yield normal results and conventional imaging will potentially miss half of the micro-lesions. Modern algorithms should focus on the combination of TRH testing and trial of depot somatostatin analogue, in order not to miss the diagnosis. SPGR MRI and functional pituitary imaging with 11C-Methionine can be used to detect microlesions that are not visible on conventional pituitary MRI sequences, thus facilitating targeted treatment.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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