Endocrine Abstracts

A 73-year-old female with previous tuberculosis, primary hypothyroidism, depression and caecal cancer was referred to Endocrinology when interval CT scanning reported a 2.5 cm adrenal mass, stable in size over 4 years. No symptoms or signs of hormonal production were noted. Screening tests were abnormal: post-1 mg dexamethasone cortisol was 98 nmol/l, 24-h urinary free metadrenaline was elevated tenfold (3256 nmol/24 h, range 0–350) to a concentration reported to have high positive predictive value for phaeochomocytoma. Repeat sampling was confirmatory. Venlafaxine was suspected as causative and following discussion with psychiatry was substituted with sertraline. The 24-h urinary free metadrenaline normalised and has remained stable. Low-dose and high-dose dexamethasone suppression tests confirmed sub-clinical Cushing’s syndrome related to an adrenal adenoma. Absent clinical features, reassuring DEXA and urinary cortisol:creatinine ratios favoured an observational approach.

Venlafaxine is a serotonin and noradrenaline reuptake inhibitor. Case reports have described modestly elevated catecholamine metabolites in patients prescribed venlafaxine with 24-h urinary noradrenaline elevated 1.6-fold¹ and plasma normetanephrine fourfold². This case identified substantially elevated urinary metadrenalines at concentrations usually associated with phaeochromocytoma, which then normalised upon discontinuing venlafaxine. Caution is required when interpreting catecholamine results in patients prescribed SNRI’s or other psychoactive medications due to the potential for false-positives³ and elevated catecholamines metabolites do not necessarily indicate phaeochromocytoma. Reports in the endocrine literature which defined the sensitivity and positive predictive value of 24-h urinary catecholamine metabolites in diagnosing phaeochromocytoma³ may require reappraisal in view of the increasing utilisation of SNRI’s and other novel psychoactive medications known to interfere with catecholamine metabolism.

1. Endocrine Abstracts 2007 14 P482.

2. NEJM 2011 364 (23) 2268–70.

3. JCEM 2003 88 2656–66.