Endocrine Abstracts

Introduction: Phaeochromocytomas and paragangliomas (PPGLs) are rare tumours with high morbidity. The majority are benign and surgically curable, but genetic testing suggests that many are associated with germline mutations, and careful long-term follow-up of patients and their family members is important. Regular biochemical screening with plasma or urinary metanephrines (uMetanephrines) is essential, but currently 24-h collections of uMetanephrines is cumbersome and inconvenient for patients.

Objective: Our aim was to compare 24 h uMetanephrines with ‘spot’ samples of random urines in patients under investigation or follow-up for PPGLs.

Design, materials and methods: Prospective diagnostic study of 59 patients (mean age 51.3±17.3 years, range 22–80): 18 with adrenal incidentalomas, nine with symptoms suggestive of PPGLs, four carriers of mutations associated with PPGLs, 11 follow-up of operated PPGLs, eight with surgically-verified PPGLs and nine metastatic PPGLs, evaluated at a university hospital from December 2015 to May 2016. The 24-h sample and a simultaneous urinary random spot (20 ml) were assayed for normetanephrine (NMT), metanephrine (MT) and 3-methoxytyramine (3MT) using mass spectrometry. The random samples were corrected for creatinine.

Results: We found a significant correlation between spot concentrations (μmol/mmol creatinine) and output of NMA (r=+0.987), MA (r=+0.995) and 3MT (r=+0.865) for all patients, especially in patients with PPGLs (new diagnosis and metastatic) (NMA r=0.997; MA r=0.999, 3MT r=0,998; P<0.001). We derived thresholds for 100% specificity to predict 24-h urinary results in diagnosing excessive catecholamine secretion.

Conclusion: The ratios of NMA, MA and 3MT to creatinine in spot urine samples correlate with the output of these metabolites in 24-h collection, with similar sensitivity and specificity for diagnosis of PPGLs and metastatic disease.

We propose spot random urinary threshold that could be used to diagnose excessive catecholamine secretion, simplifying patient requirements without loss of accuracy.