adrenal gland 2 Flashcards
metabolic roles of cortisol
↑ Gluconeogenesis to maintain blood glucose levels
↑ Glycogen synthesis to maintain glucose storage
↑ Protein catabolism
↑ Lipolysis
↑ Appetite
↑ Insulin resistance
non-metabolic roles of cortisol
Immune system: antiinflammatory and immunosuppressive effects
Wound healing: ↓ wound healing
Blood pressure: mild mineralocorticoid effect, ↑ blood pressure
why does cortisol limit wound healing
fibroblast inhibition → ↓ collagen synthesis → ↓ wound healing
why does cortisol increase blood pressure
mild mineralocorticoid effect (stimulation of aldosterone receptors in high concentrations) and ↑ potassium excretion → ↑ blood pressure
what promotes secretion of glucocorticoids in the adrenal cortex
CRH from the hypothalamus stimulates ACTH in the pituitary gland which stimulates secretion of glucocorticoids from the adrenal cortex
ACTH stands for
adrenocorticotropic hormone
what triggers CRH release from the hypothalamus
Psychological/physical pain and stress
Pyrogens, epinephrine, histamine
Hypoglycemia
Hypotension
what is the negative feedback mechanism for cortisol
Cortisol inhibits the secretion of CRH and ACTH via negative feedback, which, in turn, results in a decrease in cortisol secretion.
what triggers the rhythmic release of CRH
impulses by the suprachiasmatic nucleus trigger the rhythmic release of CRH, the SCN also transmits signals directly to the adrenal cortex via neural pathways
what does 5a reductase do
coverts testosterone into dihydrotestosterone (DHT)
what do 5a reductase inhibitors do
inhibit the conversion of testosterone into dihydrotestosterone (DHT) via 5a-reductase
eg. finasteride
what hormones are created in the adrenal medulla
catecholamines
eg. noradrenline, adrenaline, dopamine
where else are catecholamines synthesised
Catecholamines (norepinephrine, epinephrine, dopamine) can also be synthesized in specific regions of the CNS eg. substantia nigra and locus coeruleus and postganglionic adrenergic neurons.
which catecholamine has the shortest half life
adrenaline
how are catecholamines degraded
via catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO)
what do monoamine oxidase inhibitors do
elevate catecholamine concentration in the synaptic cleft
what activity does adrenaline have
both a and b adrenergic agonist activity
causes bronchial smooth muscle relaxation, cardiac stimulation, peripheral vasodilation (small doses) and peripheral vasoconstriction (large doses)
what is vanillylmendelic acid (VMA)
an end stage metabolite of catecholamines
Urinary excretion is elevated in patients with pheochromocytoma and neuroblastoma.
What is a pheochromocytoma?
A catecholamine-secreting tumor that develops in the adrenal medulla.
What percentage of pheochromocytomas are malignant?
Approximately 10%.
What are the symptoms of excess sympathetic nervous system stimulation in pheochromocytoma?
- Episodic hypertensive crises
- Paroxysmal headaches
- Diaphoresis
- Heart palpitations, tachycardia
- Pallor
- Abdominal pain, nausea
- Anxiety
other symptoms include: weight loss due to increased basal metabolism, hyperglycaemia, polycythaemia if EPO is secreted, additional features of hereditary disorders
Can pheochromocytomas be asymptomatic?
Yes, they may also manifest with persistent hypertension.
What confirms the diagnosis of pheochromocytoma?
Elevated catecholamine metabolites eg. VMA in the plasma or urine.
imaging studies are used to determine the location of the tumor
What is the treatment of choice for pheochromocytoma?
Surgical resection.
Preoperative alpha-adrenergic blockade (e.g., phenoxybenzamine) is indicated to prevent intraoperative complications such as hypertensive crises.
