Disorders of the human adrenal gland Flashcards
What is adrenal insufficiency?
Inadequate adrenocortical function
What causes primary adrenal insufficiency?
o Addison’s disease
o Adrenal TB/malignancy
o Congenital Adrenal Hyperplasia (CAH) = neonatal form
What can cause secondary adrenal insufficiency?
Due to lack of ACTH stimulation of the adrenal glands
- Iatrogenic (excess administration of exogenous steroid)
- Pituitary/hypothalamic disorders
What causes congenital adrenal hyperplasia?
genetic disease:
- autosomal recessive
= lack of 21-hydroxylase activity
= deficiency of cortisol and aldosterone
= increased adrenal androgens
What is the significance of lack of 21-hydroxylase activity?
most important enzyme in aldosterone and cortisol production
How do boys present with CAH?
adrenal insufficiency
How do girls present with CAH?
masculinisation of female genitalia due to
excess exposure to androgens in utero
What is Addison’s disease?
Autoimmune destruction of adrenal cortex
o >90% destroyed before symptomatic
o Autoantibodies positive in 70%
What are the clinical features of Addison’s disease?
Non-specific symptoms o Anorexia, weight loss o Fatigue/lethargy o Dizziness and low BP o Abdominal pain, vomiting, diarrhoea o Skin pigmentation (should not be missed!) on palmar creases and buccal mucosa
Symptoms are often precipitated by an intercurrent illness
What tests are used to diagnose adrenal insufficiency?
- electrolyte derrangement
- Short synacthen test
- High ACTH levels
- high renin
- low aldosterone
- adrenal autoantibodies
Describe biochemistry results in adrenal insufficiency
marked electrolyte derangement
- Low Na
- High K
- hypoglycaemia
Describe the short synacthen test
SYNACTHEN = synthetic ACTH
- Stimulate cortisol
- Measure plasma cortisol before and 30 minutes
after IV ACTH injection
Normal: baseline >250nmol/L, post ACTH >;480
Describe the ACTH levels in adrenal insufficiency
Increased
- Pituitary attempts to stimulate cortisol production
- This is what causes skin pigmentation
Describe the renin levels in adrenal insufficiency
Raised renin because of stimulation by RAAS
Describe the aldosterone levels in adrenal insufficiency
low
- causes hyperkalaemia and hyponatraemia
How is adrenal insufficency treated?
- Hydrocortisone as cortisol replacement
- Fludrocortisone as aldosterone replacement
Why is hydrocortisone used in adrenal insufficency?
Metabolised to cortisol. Most physiological way of replacing cortisol
Describe treatment pattern of hydrocortisone in adrenal insufficiency
If unwell, give intravenously first
o Then 15-30mg oral tablets daily in divided doses (for long-term maintenance)
o Try to mimic diurnal rhythm
Highest levels in the morning, therefore give higher dose in the morning
What is the significance of adrenal insufficiency
- untreated = fatal
(Do not delay treatment to confirm diagnosis)
‘sick day rules’ – double oral hydrocortisone for 3 days when unwell
o Cannot stop suddenly, as this will cause adrenal crisis
o Need to wear identification
What are the main causes of secondary adrenal insufficiency?
(LACK OF CRH/ACTH)
- pituitary/hypothalamic disease (tumour, surgery, radiotherapy)
- exogenous steroid use
How does exogenous steroid use cause secondary adrenal insufficiency?
Commonest cause
o Risk for patients on exogenous steroids for
> 6 weeks (possibly even >3 weeks)
o Negative feedback of endogenous steroids
on CRH/ACTH
What are the clinical features of secondary adrenal insufficiency?
similar to Addison’s EXCEPT:
o Skin pale (no ACTH, therefore no pigmentation)
o No electrolyte abnormalities as aldosterone production is intact (regulated by RAAS)
How is secondary adrenal insufficiency treated?
hydrocortisone replacement
What is Cushing’s syndrome?
Excess cortisol secretion
