Adrenal Medullary Disease Flashcards
Adrenal medulla anatomy and functions
Center of the adrenal gland and contains the superior adrenal vein to drain venous
Is produced from the ectoderm neural crest cells
Secretes epinephrine and norepinephrine in response to stress and autonomic sympathetic and parasympathetic nervous system. Not really controlled by the pituitary gland
- primarily autonomic sympathetic
Sympathetic nerves dont synapse on the chain and instead go straight to the adrenal medulla from the preganglia found before the sympathetic chainand synapse (T8 and T12 are the primary sympathetic nerve roots)
- preganglionic = straight from nerve root to adrenal medulla. Binds to N2 receptors and uses Ach
Secretes 80% epinephrine and 20% norepinephrine
- because of this there is more alpha-receptor responses
How do non adrenal medulla sympathetic neurons work?
Preganglionic = synapse onto the sympathetic chain via N2 receptors and ACh neurotransmitter
Post ganglionic smooth muscles and non-sweat glands = binds to a1/2 or b1/2 receptors and NE neurotransmitter
Post ganglionic sweat glands = binds to M1/2 receptors and ACh neurotransmitter
What enzymes break down catecholamines
COMT = makes metanephrine and noremetanephrine
MAO = dihydroxymandelic acid
The combo of these two form VMA
All is excreted in the urine
Why is hypofunctioning adrenal medulla almost never present with any serious symptoms?
Because the rest of the body (testes and sympathetic nervous system) can accommodate the hypofunction
Pheochromocytoma
A rarer cause of secondary HTN Caused by a catecholamine secreting tumor
Causes paradoxical triad of (usually once a month) 1) headache 2) sweating 3) tachycardia Along with HTN
Note 50% of these are asymptomatic
Other possible symptoms:
- pallor
- tremors
- palpitations
- feelings of being scared
- chest pain
Rates = 5:1,000,000 (1600 total per year)
- more common in 30-50yrs and found in equal amounts of males and females
What are other common things that cause a pheochromocytoma presentation
Anxiety
Cardiac arrhythmia and angina
Hypoglycemia
Thyrotoxicosis
Postural tachycardia syndrome (POTS)
- essentially opposite of orthostatic
When to really suspect pheochromocytoma
1) all classic triad symptoms
2) ruled out other hyperadenergic spells/causes and HTN is resistant
3) incidental adrenal mass is present with patient who has classic triad Symptom(s)
4) family history of pheochromocytoma
What are the most common genetic syndromes of pheochromocytoma
MEN type 2 = 50%
VHL = 10-20%
NF type 1 = 2-3%
If a patient has a one of these = screen for pheochromocytoma. Also vise verse
Diagnosis of pheochromocytoma
High levels of catecholamines and
- vanillymandelic acid
- norepinephrine and metanephrine
Use a 24 hr urine collection to do this
- *can also use the plasma free metanephrine
- have patient lay down and draw blood after 30 minutes and then draw free levels of metanephrines. (If high = likely pheochromocytoma)
- *both tests have high risk of false positive specially if
- older patient
- taking TCA’s, amphetamines or decongestants (stop these before biochemical testing)
Imaging for pheochromocytoma
Can use either CT or MRI of the abdomen (neither is really first line)
Has a 30% chance of getting a false positive
note in order to induce surgery = needs symptoms, labs and imagining to all be postive for pheochromocytoma
Paragangliomas
Are another super rare subset of catecholamine producing tumors that are in the adrenal glands
Often only considered if you are working up a pheochromocytoma and you get positive symptoms and labs but NEGATIVE imaging
Can still catch this on imaging but requires specific testing
What types of specialized imaging is used for pheochromocytoma and paragangliomas
Iobenguane I-123 (MIBG)
- inject a substance similar to norepinephrine and is taken up by adrenergic tissues That are detected on imaging
- used to retest small catecholamine producing tumors
Fludeoxyglucose-positron emission tomography
(FDG-PET)
These differentiate the two if you still suspect them
Treatment of pheochromocytoma and paragangliomas
Solitary masses = surgery with a/b blockers first
- get a microscopic imaging to confirm diagnosis.
If Mets = same as above but also give Iobenguane I-131 as radioactive iodine that destroys the catecholamine producing tumors
- also give chemotherapy
How to monitor pheochromocytoma and paraganglioma for remission
All patients need to monitored for labs and periodic CT/MRIs
All have a risk of returning (larger tumors have high risk) and you cant tell the difference between metastatic and benign pheochromocytoma with histology
Neuroblastoma
Only suspected if you feel an abdominal mass on the abdomen in children (always shows this)
- also may show paraneoplastic symptoms as well as bone pain and liver symptoms (for metastasis)
3rd most common cancer in children after retinoblastoma and leukemia
- 40% occur before age 1 and account for 15% of all pediatric cancer deaths
Are derived from sympathetic ganglion cells and most occur in the sympathetic chain (60%) and the adrenal medulla (40%)
Also produce catecholamines but don’t show as obvious of symptoms
