Adrenal medulla hormones 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: Increase heart rate. Increase blood pressure. Dilation of eye pupils. Decrease stomach and intestinal motility. 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) 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.