Endocrine Abstracts

Introduction: Phaeochromocytoma is a rare condition. It presents with non-specific symptoms of palpitations, headache and hypertension. Such symptoms in a patient with background of previous medullary thyroid carcinoma cannot be ignored and would warrant further investigation to exclude MEN II.

Case report: A 45-year-old gentleman presents with labile hypertension, headaches and palpitations. He has a history of a recurrent medullary thyroid carcinoma previously managed with total thyroidectomy and external beam radiotherapy. He has been on 225 μg thyroxine with a fully suppressed TSH of <0.02 mU/l. Phaeochromocytoma was suspected and investigated given his persistent symptoms. Three separate collections of urinary catecholamines have shown borderline excess production of urinary free noradrenaline between 635 and 944 nmol/collection (NR <601 nmol/collection). Subsequent imaging with an Octreotide whole body scan has shown no evidence of adrenal pathology with evidence of uptake around the supraclavicular region in keeping with a recurrence of medullary thyroid carcinoma. The patient’s plasma normetanephrine was subsequently found to be normal at 585 pmol/l (NR 120–1180). This gentleman’s thyroxine replacement was reduced to 175 μg to attain a biochemical euthyroid state. Both his symptoms and urinary catecholamines returned to normal as they were iatrogenic rather than due to phaeochromocytoma. Genetic testing confirmed RET oncogene as negative.

Conclusion: Biochemical investigations and confirmatory tests for phaeochromocytoma should be evaluated in light of other co-existing endocrine pathologies such as thyroxine replacement therapy. Management of medullary thyroid carcinoma with thyroxine should aim at attaining a euthyroid biochemical profile rather than supra-physiological replacement.