Endocrine Abstracts

Introduction: The performance of biochemical and imaging investigations in contributing towards successful surgical outcomes is not well characterised in PHPT.

Methods: Retrospective analysis of all patients presenting to the Edinburgh Centre for Endocrinology & Diabetes with PHPT between 2006 and 2014 (n = 611). Parathyroid surgery was performed in 44.8%.

Results: PTH was greater than 2x ULN in 34.3%, above ULN but not greater than two-fold in 54.5% and within reference range in 11.1%. Vitamin D deficiency was present in 32.6% (135/413). Urine CCCR was <0.01 in 18.1% of surgically confirmed cases of PHPT. Vitamin D status and spot-sample versus 24-hour urine collection was not associated with differences in CCCR. 247/375 (65.9%) neck ultrasound scans identified an adenoma. In surgically confirmed cases, only older age (P<0.001) was identified as a risk factor for failing to identify an adenoma on ultrasound. Ultrasound determined laterality was correct in 172/182 (94.5%) cases at surgery where an adenoma was identified. 144/220 (65.4%) sestamibi scans showed significant uptake – the following factors were associated with uptake: greater tumour dimension (P<0.001), higher PTH (P<0.01) and higher adjusted calcium (P<0.05). Structural lesions were noted in 64/93 (68.8%) SPECT CT scans. Surgical failure was 5% where one imaging modality was employed, 13.7% with 2, 10.5% with 3 and 20% with 4. Thyroid US was associated with 7.8% treatment failure, Sestamimbi with 11.6%, SPECT CT with 8.6% and 4DCT with 30.8%.

Conclusion: The vast majority of PHPT is associated with a frankly elevated PTH concentration. The likeliest diagnosis in patients with low CCCR is still overwhelmingly PHPT. Confident diagnosis of an adenoma on US is associated with satisfactory surgical outcome. When multiple imaging modalities are required, success rates are predictably lower. A gold-standard modality is required, early experience with 11C-Choline PET holds some promise.