Neuroendocrine Tumours, Apoplexy and other Endocrinology

Question 1

What is the epidemiology of carcinoid tumours?

Answer 1

Rare…

Question 2

What is the pathophysiology of carcinoid tumours?

Answer 2

They are slow growing tumours of the neuroendocrine system (NETs), of enterocromaffin origin - capable of producing 5HT*

May also secrete:

• Bradykinin
• Substance P
• Gastrin
• Insulin
• Glucagon
• ACTH
• PTH
• T4

Grow in:

• Appendix
• Ileum
• Rectum
• Stomach
• Lungs

Most are asymptomatic - incidental findings - but have malignant + metastatic potential

Question 3

How do carcinoid tumours present?

Answer 3

Those that secrete hormones etc cause carcinoid syndrome (a paraneoplastic syndrome):

• Flushing of skin on head and upper thorax
• Serotonin induced fibrosis of valvular endocardium - valvular disease (tricuspid, pulmonary)
• Serotonin excess leads to tryptophan depletion -> niacin deficiency (=pellagra) -> dermatitis, diarrhoea, dementia
• Bronchoconstriction (histamine induced)
• Appendicitis (because of location of tumour)

990% of patients have metastatic disease

Question 4

How do you investigate carcinoid tumours?

Answer 4

Will depend on location e.g. bronchoscopy, colonoscopy; usual CT for staging

Blood - may contain high amounts of catechoelamines etc, depending on what tumour is secreting

Urine - may contain excessive serotonin byproducts (5HIAA - 24hr monitoring)

Question 5

What is a carcinoid crisis?

Answer 5

When a carcinoid tumour outgrows its blood supply or is handled too much in surgery - large release of inflammatory mediators - life threatening vasodilatation, hypotension, tachycardia, bronchoconstriction, hyperglycaemia

Manage the physiological complications + treat the tumour

Question 6

How do you manage carcinoid tumours?

Answer 6

High dose octreotide

• Somatostain analogue which decreases serotonin secretion
• Will reduce symptoms (diarrhoea, flushing)
• May also slow growth of tumours

Surgery - for primary tumours

Hepatic artery embolisation - if in liver

Question 7

What is a phaeochromocytoma?

Answer 7

Rare adrenal tumour arising from chromaffin cells of adrenal medulla

Secrete catecholamines, notably NAd; also CTRH

Question 8

How do phaeochromocytomas present?

Answer 8

Sympathetic hyperactivity:

• Diaphoresis (excess sweating)
• Headaches
• Tachycardia

Also:

• Flank pain
• Skin sensations
• Elevated BP: sometimes paroxysmal so hard to detect; sometimes malignant/resistant to treatment - leading to end organ damage
• Anxiety/panic attack
• Hyperglycaemia (from catecholamine stimulation of lipolysis)
• Weight loss

Question 9

What is a phaeocromocytoma crisis?

Answer 9

Massive release of catecholamines resulting in a hypertensive emergency - resistant arterial HTN + damage to myocardium

May occur spontaneously or as a result of tumour manipulation, pharmacological agents, even certain foods etc.

Question 10

How do you diagnose phaeochromocytma?

Answer 10

Plasma or 24hr urine catecholamines + metanephrines

CT/MRI - 80% are unilateral and solitary

Question 11

How do you treat phaeochromocytoma?

Answer 11

Resection of the tumour

Pre/perioperative treatment with alpha blockers e.g.
- doxazosin, prazosin etc.

Question 12

What is pituitary apoplexy?

Answer 12

Bleeding or ischemia of the pituitary gland

Usually occurs in the presence of a pituitary tumour (nearly always a benign pituitary adenoma) - but often can be first presentation of such a tumour

Sheehan’s syndrome = apoplexy following blood loss during pregnancy

Also occurs as a result of usual risk factors for bleeds e.g. HTN, anticoagulation etc.

Question 13

How does pituitary apoplexy present?

Answer 13

Acute:

• Sudden headache
• Rapidly worsening visual field defect - caused by compression of optic nerves/chiasm/tracts and/or - Double vision from compression of extraoccular muscle nerves in the cavernous sinus
• N+V +/- other signs of meningism

Sub-acute/chronic:

• Possible panhypopituitarism, depending on severity
• ACTH loss = most obvious/significant initially - lack of cortisol production leads to an Addisonian crisis (critically low BP. hypoglycaemia, abdo pain)
• TSH deficiency = hypothyroid
• Gonadotropin deficiency (libido, infertility and menstrual disturbance)

Question 14

How do you manage pituitary apoplexy?

Answer 14

MRI:
- More sensitive than CT in this instance

Bloods:

• Are they producing ACTH? (if not = secondary adrenal insufficiency, needs treatment stat)
• U+E (hyponatraemia can be an issue) + glucose

Stabilisation of circulation (due to hypocortisolism):

• IV fluids + destrose
• IV/IM high dose corticosteroids

Resection of tumour if present and large/still growing significantly - ?trans-sphenoidal resection of tumour

Will need proper follow up to assess levels of hormones produces +/- lifelong replacement

Question 15

What is a MIGB scan?

Answer 15

Radioisotope scan used to identify locations of NETs (specifically phaeochromocytoma and neuroblastoma)

Named after the chemical ‘iodine-131-metaiodobenzylguanidine’ or MIBG for short, to which the isotope is attached

Images obtained with gamma rays