Endocrine Abstracts

Case History: A 61 year old woman on haemodialysis with end stage renal failure secondary to immune-complex mediated diffuse proliferative glomerulonephritis was admitted with accelerated hypertension presenting with acute right microvascular 6th nerve palsy and left optic nerve ischaemic atrophy. Her BP had been well controlled over the last 10 years but since the end of 2020 systolic BP readings were frequently recorded above 200mmHg. Multiple antihypertensive classes were commenced during admission. She was discharged on maximum doses of doxazosin, bisoprolol, nifedipine, hydralazine and isosorbide mononitrate. Phenoxybenzamine, labetalol and GTN patch were later added. Admission was complicated by severe faecal impaction requiring emergency laparotomy and subtotal colectomy with end-ileostomy.

Investigations: 24 hour urine metadrenalines were within reference range, albeit with a low urine volume 323mL; normetadrenaline:0.64umol/d(0 - 3.3), metadrenaline:0.08umol/d(0 - 1.2), methoxytyramine:0.05umol/d(0 - 2.5). Plasma catecholamines showed elevated noradrenaline; noradrenaline:43.49 nmol/l(0 – 5), adrenaline: 1.28 nmol/l(0 – 8). Aldosterone/Renin ratio: 84.1. Overnight Dexamethasone Suppression Test; Serum cortisol 40 nmol/l showing adequate suppression. CT Abdomen and pelvis with contrast demonstrated haemorrhage into a 4.5 x 4.5 cm supra-renal soft tissue density mass, with resolution of haemorrhage at interval scanning. NM Tc99m HYNIC-TOC WB SPECT CT (Tektrotyd) demonstrated a high-grade somatostatin receptor positive right adrenal mass suggestive of functioning somatostatin avid lesion and focal uptake posterior to right lobe of thyroid.

Treatment: She had two further admissions due to severe uncontrolled hypertension. Despite multiple anti-hypertensive agents her BP remained poorly controlled. She was referred to tertiary care in London for management of uncontrolled hypertension and surgery for phaeochromocytoma. She was started there on GTN infusion. Subcutaneous octreotide injections were tried to slow gastric motility and improve absorption of anti-hypertensive medications due to concerns of poor absorption in view of previous GI surgery. GTN was switched from infusion to patch. She was also started on clonidine patch. Management options were discussed which included alpha and beta blockade, surgery and external beam radiotherapy. Anaesthetic assessment concluded there were significant surgical risks, and she therefore is being managed conservatively with alpha and beta blockade. Her systolic BP readings now range between 125-170mmHg.

Conclusion: Diagnosis of phaeochromocytoma can be challenging in patients with end stage renal disease on haemodialysis. Phaeochromocytomas overexpress somatostatin receptors. This can be utilised in somatostatin receptor scintigraphy using Tc99m HYNIC-TOC. Somatostatin receptor analogs are also being used in treatment of phaeochromocytomas. Addition of clonidine can be useful in those with challenging hypertension.