Adrenocortical function and dysfunction Flashcards
Briefly describe the anatomy/histology of the adrenal gland?
Inner medulla: modified sympathetic ganglion
Outer cortex: true endocrine gland
2 endocrine glands of different embryological origin that fused during development
List the hormones secreted from the adrneal gland, including the location from which they are secreted?
MEDULLA
Catecholamines
CORTEX
Zona reticularis: sex hormones
Zona fasiculata: glucocorticoids
Zona glomerulosa: mineralocorticoids
Where are glucocorticoids and sex hormones released from?
Sex hormones primarily from reticularis, also a little from fasiculata
Glucocorticoids primarily from fasiculata, also a little from reticularis
Describe the pathway for steroid hormone synthesis?
What determines the production of steroid hormones by cells?
Cells produce different hormones because they have different enzymes present
Describe the HPA pathway for control of cortisol secretion?
Describe the functions of CRH and ACTH, other than that in the HPA axis?
Stress related functions in immune and nervous systems
CRH: effects on inflammation and immune response, inhibition of appetite, signlas onset of laboor, linked to mood disorders
What is POMC?
Pro-opiomelanocortin
Large protien that yields several bioactive peptides by proteolysis
List some of the bioactive peptides yielded from POMC?
Anterior pituitary: ACTH, b-endorphins
Outside pituitary: a-MSH
Describe the effect of a-MSH?
Melanocyte-stimulating hormone > decrease food intake and increase skin melanin
How does cortisol protect against hypoglycaemia?
Stimulates catabolism of energy stores
How does the action of cortisol relate to glucagon and catecholamines?
Cortisol is permissive for the actions of glucagon and catecholamines
Describe the actions of cortisol?
Promotes gluconeogenesis in liver
Causes breakdown of skeletal muscle proteins
Enhances lipolysis
Immune suppression
Causes negative calcium balance (decreased absorption, increased excretion, bone breakdown)
Adaptation to stress
Influences brain function
Describe the effect of cortisol on calcium in the body?
Causes negative calcium balance, by decreasing absorption, increasing excretion and bone breakdown
Describe the effects of long term cortisol use as a therpaeutic drug?
Inhibition of ACTH secretion (negative feedback)
Atrophy of cortisol secreting cells
So, must taper doses gradually
How is cortisol transported in the circulation?
Corticosteroid binding globulin
What is the half-life of cortisol?
60-90 minutes
Describe the factors affecting cortisol release?
Circadian rhythm of tonic secretion
Stress enhances release
Where is the target receptor for cortisol located?
Most tissues
Intracellular (lipophilic)
Which disorders are associated with hypersecretion from the adrenal cortex?
Hyperaldosteronism
Cushing’s syndrome
Adrenogential syndrome
What causes adrenogenital syndrome?
Lack enzyme in cortisol steroidogenic pathway > pushes away from cortisol production and towards sex steroid production
What are the effects of adrenogenital syndrome?
Inappropriate masculinisation in all but adult males
How is adrenogenital syndrome treated?
Treat with glucocorticoids > repairs glucocorticoid deficit and inhibits ACTH > reduced steroid secretion
Which disorders are associated with hyposecretion from the adrenal cortex?
Addison’s disease
Adrenal steroid enzyme defects
Cortisol deficiency
Describe the hormones associated with the adrenal medulla?
Chromaffin cells secrete neurohormones
Catecholamines (adrnealine, NA, dopamine)
Why is adrenaline only produced in the adrenal medulla?
Enzyme for conversion to adrenaline from NA (PNMT) only present in adrenal medulla
Describe the adrenomedullary hormone actions?
Fight or flight: increase cardiac rate, contractility, TPR and BP
Metabolic: increase glucose and FFA, increase BMR
Central: increase arousal and alertness
Stess responses
Which disorders are associated with hyposecretion from the adrenal medulla?
None recognised
Which disorders are associated with hypersecretion from the adrenal medulla?
Pheochromocytomas
Describe the two types of stress and their responses?
Acute: fight-or-flight reaction
Chronic: elevates cortisol levels
Briefly describe the physiology of a stress response?
