Endocrine Abstracts

A 50 year-old lady was referred to the endocrine service for evaluation of significantly elevated 3-methoxytyramine (3-MT) levels. Past medical history included well controlled HIV and hypertension controlled by a single agent only (amlodipine). On one occasion, she was noted to have an elevated systolic blood pressure of 189 mmHg in clinic and therefore 24 h urinary metanephrines were requested. She did not have any other symptoms to suggest excess catecholamines. Systems review was unremarkable. There was no family history of endocrinopathies. She had recently been diagnosed with multiple system atrophy. A Dopamine Active Transporter scan revealed reduced uptake at the basal ganglia. She had been started on Sinemet 125 mg TDS by the neurologist and her symptoms, which include postural hypotension, greatly improved. In the endocrine clinic, her systolic blood pressure was 128 mmHg. The history was revisited and it transpired that on the day her blood pressure had been elevated, she had omitted her amlodipine. Physical examination did not reveal any obvious stigmata of an endocrinopathy. Blood tests showed normal electrolyte, renal function, bone profile and thyroid function. However, repeat 24 h urinary metanephrines were a follows: Metanephrine 488 nmol/24 h (NR 0-2000), normetanephrines 1139 nmol/24 h (NR 0-4400) and 3-MT 20 424 nmol/24 h (NR 0-2500). This confirmed a previous 24 urine collection result. It was thought that the isolated markedly raised 3-MT, a dopamine metabolite, was secondary to Sinemet which is a combination of carbidopa and levodopa. Sinemet could not be discontinued as it significantly improved her symptoms. A differential diagnosis of a dopamine secreting neuroendocrine tumour was a considered. Chromogranin A & B were evaluated and were normal. Her case was discussed at the regional adrenal MDT meeting. The MDT concluded that the markedly raised 3-MT were secondary to Sinemet and no further investigations such as functional imaging would be required. Interpreting biochemical markers in the presence of influencing factors and drugs can often be challenging. Abnormal results can trigger unnecessary investigations which can be distressing to the patient. This case highlights the importance of MDT discussions in such scenarios.