Download Adrenal medulla

Adrenal medulla hormones
Adrenal medulla
Some effects of catecholamines
Biosynthesis of catecholamines
Metabolism of catecholamines
Disorder of adrenomedullary function
Pheochromocytoma
Adrenal medulla
 The central portion of the adrenal gland, the medulla, is
composed of endocrine parenchymal cells (called as
chromaffin cells), connective tissue and numerous blood
vessels and nerves.
 Its hormones norepinephrine (noradrenaline) is
neurotransmitter produced locally at nerve synapses beyond
the ganglia as well as in adrenal medulla.
 The other medullary hormone, epinephrine (adrenaline)
produces effects upon tissues and organs such as:
i. Increase heart rate.
ii. Increase blood pressure.
iii. Dilation of eye pupils.
iv. Decrease stomach and intestinal motility.
v. Induction of sweating.
Biosynthesis of catecholamines : tyrosine, the precursor, is derived primarily from dietary
source. The first step in biosynthetic pathway, the conversion of tyrosine to DOPA. DOPA is
converted DOPAMINE.
Metabolism of catecholamines:
COMT (Catechol-o-methyl transferase) MAO (monoamine oxidase)
Disorder of adrenomedullary
function: Pheochromocytoma
 These tumours arise from chromaffin cells (90% are in the
adrenal medulla; the rest can occur anywhere from the
base of the brain to the testes).
 About 5% of tumours are bilateral and about 10%
malignant.
 They secrete excessive amounts of noradrenaline,
adrenaline and the metabolites normetadrenaline,
metadrenaline and 4-hydroxy-3-methoxymandelic acid
(HMMA – also known as vanillylmandelic acid or VMA).
 Phaeochromocytoma is a rare cause of hypertension
(<0.1% of cases). Characteristically, this is episodic.
 Even when the hypertension is present all the time,
episodic attacks of symptoms (e.g. headache, pallor,
palpitations, sweating, panic attacks, abdominal pain)
tend to occur.
 Such features are important when selecting the time for
collecting specimens for certain laboratory investigations.