Adrenals - Glucocorticoids Flashcards
what does the Medulla of the adrenals secrete?
Adrenaline and noradrenaline
What does the Cortex of the adrenals secrete?
Mineralcorticoids (aldosterone) - z. glomerulosa
Glucocorticoids (cortisol) - z. fasciculata
Androgens (testosterone) - z. reticularis
Describe the hypo-pituitary-adrenal (HPA) axis
Corticotropin-releasing hormone (CRH) is secreted from hypothalamus
CRH acts on pituitary to secrete adrenocorticotropic hormone (ACTH)
ACTH acts on adrenals to secrete cortisol
which has a negative feedback on hypothalamus and pituitary
What is Cushing’s syndrome?
the clinical state as a result of chronic glucocorticoid access and loss of normal feedback mechanism of HPA axis
What are the causes of Cushing’s Syndrome?
- ACTH dependent causes
- Cushing’s disease (ACTH secreting pituitary adenoma)
- Ectopic ACTH production (from lung cancer) - ACTH independent causes
- Adrenal adenoma/cancer
- Adrenal nodular hyperplasia
- iatrogenic
- rare: Carney complex, McCune-Albright syndrome
What are the clinical features of Cushing’s syndrome?
Symptoms:
- Weight gain
- Insomnia
- Mood changes
- Acne
- Back pain
- Polyuria
- Gonadal dysfunction: irregular menses, ED
Signs:
- Moon face, buffalo hump, central obesity
- Plethoric
- Skin and muscle atrophy
- bruises, purple/red striae
- Osteoporosis
- Infection prone, poor healing
Investigation of Cushing’s syndrome?
Confirm diagnosis then localise source:
1st line: overnight dexamethasone suppression test
2nd line: 48 hr dexamethasone suppression test
If Cushing’s - no suppression of cortisol; cortisol levels still high. (no negative feedback)
Localisation:
- Plasma ACTH level:
- if undetectable, adrenal tumour; CT adrenals
- Detectable, distinguish between pituitary cause or ectopic. If high dose of dex does not suppress, ectopic cause - CRH levels.
- rises with pituitary disease but not with ectopic ACTH production
Treatment of Cushing’s syndrome?
Depends on cause:
- iatrogenic - stop meds if possible
- Cushing’s disease - remove pituitary adenoma (transphenoidally)
- Adrenal adenoma - adrenalectomy
- adrenal carcinoma - adrenalectomy + chemo
- Ectopic ACTH - surgery. pre-op ketoconazole, fluconazole.
When does hypoadrenalism occur?
- long term steroid use (suppression of HPA axis)
- Overwhelming sepsis
- Metastatic cancer
Describe primary adrenocortical insufficiency
aka Addison’s disease
- destruction of adrenal cortex leads to decrease secretion of mineralcorticoids, glucocorticoids And sex hormones.
Causes of primary adrenocortical insufficiency
- 80% autoimmune (in UK)
- TB (most common cause worldwide)
- Adrenal mets (e.g. from lung, breast and renal ca)
- Lymphoma
- opportunistic infection from HIV
Clinical features of primary adrenocortical insufficiency
- Weight loss, fatigue, anorexia
- Pigmented palmar creases and buccal mucosa
- Myalgia, arthalgia
- depressed, psychosis, low self esteem
- dizzy faint, hypotension (low aldosterone)
- GI: N&V, abdo pain, diarrhoea and constipation
Investigation of primary adrenocortical insufficiency
- Bloods: U&Es - low Na+, high K+, low glucose
Plasma renin & aldosterone - Synacthen test (short ACTH)
- 21-hydroxylase adrenal autoantibodies
- AXR/CXR (past tb/adrenal calcification)
Treatment of primary adrenocortical insufficiency
Replace steroids daily (hydrocortisone)
Replace mineralcorticoids (fludrocortisone)
*Adjust both on clinical response
*Educate pts on long term steroid use. Danger in stopping, increase if sick/exercsing, decrease if vomiting/not eating
Causes of secondary adrenocortical insufficiency
iatrogenic due to long-term steroid therapy leading to suppression of pituitary-adrenal axis
