Endocrine Abstracts

59-year-old gentleman with known succinate dehydrogenase complex subunit C (SDHC) gene mutation attended endocrine clinic with non-specific symptoms. Past medical history included glomus jugulare paraganglioma (PGL) surgically treated (1993, 2003) with residual disease, macroprolactinoma treated with cabergoline since 2010, and BPH treated with finasteride and tamsulosin. His brother has glomus vagale. Clinical examination was unremarkable. Plasma metanephrine ranged between 377 and 458 pmol/l (120–1180 pmol/l), and plasma normetanephrine ranged between 284 and 349 pmol/l (80–510 pmol/l). Plasma 3-MT was 1014 pmol/l (0–180 pmol/l) whilst on cabergoline 250 μg/wk. When cabergoline stopped for 4 weeks plasma 3-MT increased to 2185 pmol/l, and when cabergoline recommenced plasma 3-MT dropped to 1272 pmol/l. Possibly, as cabergoline as a dopamine D2 receptor agonist, it would be expected to exert negative feedback on the dopamine system and lower endogenous dopamine production, and therefore lower its metabolite (3-MT). MRI-whole-body showed stable appearances of the residual disease in the right jugular foramen with no other lesions. ⁽¹²³⁾I-MIBG showed probable residual right jugular foramen disease without other avid lesions. ⁽⁶⁸⁾Ga-DOTATATE PET/CT showed multiple foci increased avidity at the right skull base, and avid uptake in the sacrum suggestive of metastasis. Following MDT discussion ⁽¹⁷⁷⁾Lu-DOTATATE ablation therapy was recommended. Co-existence of PGL and pituitary macroadenoma is a recognised rare syndrome, whether this is a coincidence or the result of a genetic defect, it remains unanswered. Isolated rise 3-MT is very rare, and it may the only positive biomarker in PGL, therefore in PGL patients 3-MT should be a part of the surveillance along with plasma metanephrine and noremetanephrine. ⁽⁶⁸⁾Ga-DOTATATE PET/CT is superior to ⁽¹²³⁾I-MIBG scan in the detection of metastatic PGL. To date we describe the first case in which elevation of 3-MT prompted further testing and the diagnosis of metastatic PGL in SDHC mutation.