(1.14) Dopaminergic medications as confounding factor for functioning adrenal adenoma

The incidence of adrenal incidentalomas has increased over the last years. Most lesions are benign but approximately 10 to 15% secrete excess hormones. Determining the risk of malignancy and whether it is functioning is important to guide management. Catecholamines and metanephrines are part of the testing to assess for hormone excess. The diagnosis of catecholamine-producing tumors in patients with Parkinson's disease taking dopaminergic drugs can be challenging due to confounding factors in biochemical tests.

Case(s) Description :

A 67-year-old woman with a history of Parkinson’s disease on levodopa-carbidopa and controlled hypertension presented to the clinic with intermittent palpitations, diaphoresis, and flushing for 1.5 years. No known family history of endocrine or autoimmune conditions. Laboratory work-up revealed markedly elevated serum and urinary dopamine levels. Fractionated urinary dopamine was elevated at 4505 ug/24 hr (normal 65-400), urinary Vanillyl-Mandelic Acid (VMA) levels were mildly elevated to 9.8 mg/24 hour (Normal = or < 6) and norepinephrine at 92 ug/24 hr (normal 15-80). Urinary Epinephrine was normal. Additional laboratory work was ordered including TSH, chromogranin A, serum aldosterone, direct renin, which were normal, aldosterone: renin ratio was 1.5, cortisol levels following 1 mg dexamethasone suppression was 4.3, late salivary night cortisol and DHEA-sulphate were normal. Patient underwent CT abdomen with IV contrast which revealed a 2.5 cm lipid rich left adrenal mass measuring 35 HU pre- contrast, 76 HU post- contrast and 50 HU in delayed imaging. Initial plan was to hold levodopa-carbidopa for a metaiodobenzylguanidine (MIBG) scintigraphy, this was discussed with Neurology and recommended against holding it due to the severity of her parkinsonism. Repeat serum norepinephrine and epinephrine were normal, conservative approach with close follow-up was opted. A repeat CT Abdomen after 12 months showed stable findings compared to the previous one, size was unchanged. 

 

Discussion :

Dopaminergic agents can lead to false positive biochemical abnormalities indicating possible pheochromocytoma or paragangliomas. Image-based modalities are recommended to support the correct diagnosis and avoid unnecessary interventions such as adrenalectomy. Current advances in genetics are also able to identify germline mutations and molecular components of these pathologies that also help with the diagnostic challenge.