Adrenal Medulla Physiology
Bob Bing-You, MD, MEd, MBA
Medical Director
Maine Center for Endocrinology
A Case of the Sweats
• 32 y.o. white male
• 6 month h/o increased sweating; nonexertional, profuse
• Occasional h/a’s, palpitations
• Father had a “high calcium problem” and
his paternal GGM had thyroid surgery for a
tumor
Adrenal Over-production
• Adrenal Medulla
– Catecholamines, norepinephrine, epinephrine
• Adrenal Cortex – surgical disease
– Cushing’s syndrome
– Hyperaldosteronism [Conn’s Syndrome]
– Androgen-producing tumors
Adrenal medulla function
• Stimulated by sympathetic nervous system
to release epinephrine and norepinephrine
• 80% epi and 20% norepi
• Effects on tissues 10 x longer than direct
sympathetic stimulation due to slow
removal
Catecholamine effects
• Norepinephrine
–
–
–
–
Vascular vasoconstriction
Increased heart rate
Inhibit GI tract
Pupil dilation
• Epinephrine
– Greater effect on cardiac activity
– Weaker vasoconstriction [less effect on  BP]
Other effects
• Epi >> norepi increasing metabolic rate
• Support vascular “tone”
• Catecholamines support direct stimulation
of tissues activated by sympathetic system
• Back-up system for each other
Tiger fight-or-flight
•
•
•
•
•
•
•
 arterial pressure
 blood flow to all active muscles
 rates cellular metabolism throughout body
 blood glucose concentration
 glycolysis in muscle
 mental activity
 rate of blood coagulation
Catecholamine biosynthesis
• Tyrosine » dopamine » norepinenephrine »
epinephrine
• Degraded to vanillylmandelic acid [VMA]
and metanephrines
Pheochromocytoma
• Rare: 1/1000 HTN patients
– Resistant HTN, secondary cause considered
• Triad of symptoms
• Multiple Endocrine Neoplasia [MEN] Type
2A and 2 B
– “PAT”: parathyroid, adrenal pheo, medullary
thyroid cancer
– “MAT”: mucocutaneous neuromas
Case of the sweats
• 32 y.o. white male
• 6 month h/o increased sweating; nonexertional, profuse
• Occasional h/a’s, palpitations
• Father had a “high calcium problem” and
his paternal GGM had thyroid surgery for a
tumor
What MEN syndrome does he
have?
•
•
•
•
A. MEN 1
B. MEN 2a
C. MEN 3c
D. MEN 2b
Diagnosis
• Plasma metanephrines
• 24 hour urine catecholamines, sensitivity of
metanephrines > VMA
• Adrenal MRI, MIBG functional scan
• MEN2A genetic testing
Catecholamine Receptors
•
•
•
•
•
•
Alpha
-vasoconstriction
-iris dilation
-bronchoconstriction
-cardiac contractility
-hepatic glucose
production
•
•
•
•
Beta
-cardioacceleration
-bronchodilation
-lipolysis
Pre-op Rx
• Block Adrenergic receptors
• Alpha blockade before beta
– Phenoxybenzamine, phentolamine
• Beta blockade when orthostatic
– Propanolol for non-selectivity, metoprolol or
atenolol for β1 selection
• ?labetolol
Other Rx
• Hydration
• Intra-cardiac monitoring
• Severe HTN, arrhythmias
– During induction, tumor manipulation, or
anytime!
• Nipride
• Laparoscopic surgery
Surgical Outcome
• 1% operative mortality
• 5-10% recur, ?MEN syndrome
• Catecholamine levels can remain elevated
for several weeks
• Persistent HTN suggests missed tissue
• Malignant pheos 45% 5-year survival, ?I131-meta-iodo-benzylguanidine
Take-home Points
• Catecholamines needed for daily life and
stress responses
• Medulla and sympathetic system linked
• Pheos rare but one of few chances to cure
HTN
• Pre-op medical Rx important
• Operative events raises your own
catecholamines!
Reference
• Diagnostic and therapeutic strategies in
pheochromocytoma, M.S. Golub, The
Endocrinologist, 1992;2:101-6.
Questions?