Endocrine Abstracts

A 37-year-old woman, 30 weeks pregnant, presented with palpitations and abdominal cramps. Ultrasound demonstrated a supra-renal abnormality and MRI showed a 10 cm heterogeneous left adrenal mass. For five years she had experienced episodes of palpitations, shaking, sweating and chest tightness. She was investigated by a neurologist and diagnosed with temporal lobe epilepsy. During pregnancy the frequency of episodes increased. Lamotrigine was started, but at each dose increase the symptoms worsened, with attacks occurring up to three times a day.

The blood pressure was 122/84 with no postural drop. During attacks she became tachycardic but at no stage was she hypertensive. Phenoxybenzamine was commenced followed by propranolol, and symptoms completely resolved. Urinary noradrenaline was minimally raised, 769 nmol/24 h (NR 0–560), but adrenaline was very high, 1347 nmol/24 h (NR 0–144). On repeating, sample interference was found at the adrenaline peak on chromatography.

Foetal and placental ultrasound remained reassuring and an uncomplicated caesarean section was performed at 37 weeks with intravenous phenoxybenzamine pre-procedure. A healthy baby girl was delivered. Repeat urine collection post-partum off lamotrigine showed a significant improvement in adrenaline levels (320 nmol/24 h) with less assay interference and noradrenaline levels within the normal range (436 nmol/24 h). MIBG scan done at this time was positive. Left adrenalectomy was performed three months after delivery. Histology showed a highly vascular, encapsulated, completely excised phaeochromocytoma. Genetic analysis has not revealed any mutations of succinate dehydrogenase B or D.

We suggest the interference seen on urine chromatography is attributable to lamotrigine. Lamotrigine interference with urinary adrenaline measurement has not been previously reported in the literature and requires clarification. This appears to be the first reported case of a predominantly adrenaline-secreting phaeochromocytoma in pregnancy. These are rare tumours, classically associated with normotensive tachycardia as demonstrated by our patient’s predominant symptom of palpitations. The absence of hypertension may result in misdiagnosis.