Flashcards in Session 9 (2) - Disorders of Adrenal cortical function Deck (19):
What is the name for hypoactivity of the adrenal cortex?
What two factors can cause hypoactivity of adrenal cortex, and what do they cause?
Autoimmune destruction of the adrenal cortex - Reduces glucocorticoids and meneralocorticoids
Disorders in pituitary or hypothalamus that lead to decreased secretion of ACTH or CRF - only affects glucocorticoids
What is the name for hyperactivity of adrenal cortex?
What two biological factors can cause Cushing's syndrome?
Increased activity of the adrenal cortex due to adenoma
Disorders in secretion of ACTH caused by pituitary adenoma or ectopic secretions.
What is congenital adrenal hyperplasia?
Genetic defect in enzyme involved in production of cortisol. Lack of cortisol means no feedback control to pituitary, therefore large amounts of ACTH secreted. Results in adrenal hyperplasia, with various effects.
Give clinical effects of cushing's syndrome (remember the acronym)
Pissed Lions Break Into Cash Machines
Muscle proteolysis resulting in
- Hepatic gluconeogenesis + Hyperglycaemia (steroid diabetes)
- Wasting of arm and leg muscles, weakness
Lipogenesis in adipose tissue
- Fat gain in abdomen and face, resulting in central obesity and moon shaped face
Purple stria in low abdomen
- Destruction of muscle tissue under skin results in thinning and easy bruising
Immunosupressive effects of cortisol
- Increased bacterial infections and acne
Disturbances of calcium metabolism
-Osteoperosis, causing back pain and collapse or ribs
Mineralocorticoid effects of excess cortisol
- Hypertension due to sodiuma and fluid retention
What is cushing's disease?
Pituitary adenoma, causing excess ACTH production
In what two ways would too little cortisol present?
Addisonian crisis or Addison's disease
When would addison's disease be complicated by mineralocorticoid defiency?
When there is autoimmune destruction of adrenal gland NOT when it is caused by disorders in pituitary or hypothalamus secretion
Give symptoms of addisons disease
Extreme muscular weakness
Increased pigmentation on exposed areas of body, due to ACTH mediated melanocyte stimulation
Decreased blood pressure due to sodium and fluid retention (mineralocorticoid)
Postural hypotension due to fluid depletion
Hypglycaemic episodes on fasting
What happens if person suffering from addisons disease under goes stress such as trauma or infection? What are the symptoms?
Nausea, vomiting, dehydration, hypotension, confusion, fever, coma
How is addisonian crisis treated?
Intra-venous cortisol and dextrose in normal saline
What are intitial steps for investigation adrenocortical function?
Measurement of plasma cortisol and ACTH levels
Measure 24h urinary excretion of cortisol and breakdown products
Dynamic function tests (Dexamethasone supression test and Synacthen)
Outline dexamethasonn supression tests
Dexamethasone potent synthetic steroid
Would normally suppress secretion of ACTH and cortisol
Dexamethasone supression of cortisol by >50% is characteristic of Cushing's disease (diseased pituitary disease)
Why is a reading of >50% in a dexamethasone supression test characteristic of Cushing's disease?
Because for the diseased pituitary, even though it is relatively insensitive to cortisol it will still respond to potent synthetic steroid. Supression not evident in adrenal tumours or ectopic ACTH production
What does Synacthen do?
Analogue of ACTH, would normally increase plasma cortisol. Normal response usually excludes addisons disease. (but what about addisons disease caused by disorders of pituitary?)
What artificial devices can induce Cushing's syndrome
Long-term glucocorticoid steroid treatment in patients with chronic inflammatory conditions
What are the three regions of steroid receptor?
Hydrophobic hormone binding region, DNA-binding region rich in cysteine and basic amino acids and a variable region.