9. HPA Axis: Clinical Aspects Flashcards
adrenal cortex hormone production
glucocorticoid (cortisol) mineralocorticoid (aldosterone) sex steroids (androgens)
effects of glucocorticoids
maintain homeostasis during stress anti-inflammatory increase/maintain glucose levels (metabolic effects) formation of bone and cartilage regulate blood pressure cognitive function, memory
circadian rhythm - cortisol
levels rise during early morning peak just prior to awakening fall during the day low during the evening shown by mean cortisol data
ultradian rhythm
pulsatility of hormone release
spontaneous pulses of varying amplitudes
amplitude decreases in circadian trough
shown by individual cortisol data
clinical features of Cushing’s
central obesity, thin arms and legs fat deposition over upper back 'buffalo hump' rounded 'moon' face thin skin, easy bruising hirsutism hypertension diabetes osteoporosis
Cushing’s pathogenesis
pituitary adenoma: ACTH secreting cells
adrenal tumour: adenoma (or carcinoma)
‘ectopic ACTH’: carcinoid, paraneoplastic
iatrogenic: steroid treatment
clinical features of Addison’s
malaise, weakness, anorexia
increased skin pigmentation (knuckles, palmar creases, pressure areas)
hypotension/postural hypotension
hypoglycaemia
Addison’s pathogenesis
primary adrenal insufficiency (usually autoimmune in UK) - decreased production of all adrenocortical hormones
other causes of hypoadrenalism
secondary to pituitary disease (rare)
iatrogenic: stopped steroids suddenly
type 1 autoimmune polyendocrine syndrome
rare
onset in infancy
autosomal recessive
common phenotype - Addison’s, hypoparathyroidism, candidiasis
type 1 autoimmune polyendocrine syndrome
more common (still rare)
infancy to adulthood
polygenic
common phenotype: Addison’s, type 1 diabetes, autoimmune thyroid disease
type 2 autoimmune polyendocrine syndromes
more common (still rare)
infancy to adulthood
polygenic
common phenotype: Addison’s, type 1 diabetes, autoimmune thyroid disease
HPA axis assessment
basal: cortisol - blood, urine, saliva
dynamic - stimulated (dexamethasone)
management of Cushing’s
surgical (depends on cause) - transphenoidal adenectomy, adrenalectomy
pituitary radiotherapy
management of Addison’s
steroid replacement therapy (usually hydrocortisone)
if primary adrenal insufficiency, mineralocorticoid replacement
coshes must be increased to cover ‘stresses’
patients taking steroids
many reasons - usually prednisolone
usually used for anti-inflammatory/immunosuppressive effects
COPDM asthma arthritis
may suppress indigenous adrenal function if used long term at high dose (treatment should not be stopped abruptly)
