This is a case of a 49 year old obese Caucasian female who was referred to an endocrinology clinic for investigation of Cushings syndrome, based on raised blood pressure and cushingnoid facies. The patient had underlying schizophrenia and was stable on clozapine. Her blood pressure was 150/99 mmHg on bendrofluoriomethiazide and candesartan. Her 24 hour urinary free cortisol was normal but 24 hour urinary free noradrenaline was elevated at 835 nmol (76561) with normal adrenaline 36 nmol (782) and dopamine 2679 nmol (3662879), which was requested by GP as patient had history of palpitations and sweating. Two sets of 24 hour urinary free cortisol measurements were normal and serum cortisol suppressed to <50 nmol/l after a 1mg overnight dexamethasone. Two further 24 hour urinary free catecholamines showed raised level of noradrenaline. MRI demonstrated normal adrenals and MIBG scan did not show any abnormal uptake at adrenal glands. Based on these investigations, she was diagnosed to have pesudophaeochromocytoma due to clozapine, on which she was maintained at that time. She was lost to follow up and presented two years later at the hypertension clinic when she was on different antipsychotic medication, zuclopenthixol. The repeat 24 hour urinary free catecholamine as well as urinary normetadrenaline and metadrenaline were in the normal range. Urinary free noradrenaline 332 nmol, adrenaline 12 nmol and normetadrenaline 3.48 nmol (0.004.90) and metadrenaline 0.33 nmol (0.002.00).
Discussion: Pseudophaeochromocytoma has been reported in patients taking clozapine. A number of different mechanisms for raised plasma noradrenaline levels with clozapine have been postulated. These include inhibition of the synaptic re-uptake of noradrenaline, blockage of alpha-2adrenoreceptors or the combination of the two. This case was able to demonstrate the direct link of clozapine to raise urinary noradrenaline and normetadrenaline levels as these normalised after discontinuation of clozapine.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.