Adrenal Gland (hypo) Flashcards
What is the steroid precursor ?
Cholesterol
Which part of the adrenal cortex secretes aldosterone?
Zona glomerulosa
Which part of the adrenal cortex secretes cortisol?
Zona fasiculata
Which part of the adrenal cortex secretes androgens and oestrogens?
Zona reticularis
What is the overall effect of aldosterone?
Reduces potassium (Potassium excretion) Regulates sodium (sodium reabsorption) Maintains blood pressure
What are the four main enzymes involved in aldosterone synthesis within the adrenal cortex?
3-hydroxysteroid dehydrogenase
21-hydroxylase
11-hydroxylase
18-hydroxylase
What type of rhythm is exhibited by cortisol secretion?
Diurnal rhythm
What is the main cause of Addison’s disease in the UK?
Primary adrenocortical failure
(Autoimmune induced destruction of the adrenal cortex)
Atrophy of the adrenal glands.
What is the main cause of Addison’s disease worldwide?
Tuberculosis
What are the clinical features of Addison’s disease?
Increased pigmentation Autoimmune vitilgo Low blood pressure (syncope) Weight loss Fatigue Hyponatremia, hypoglycaemia, Hyperkalaemia
What is the large precursor protein of ACTH?
Pro-opio-melanocortin (POMC)
Which peptide is cleaved from POMC subsequently being responsible for hyperpigmentation within patients with Addison’s disaese?
alpha-MSH (Melanocortin-stimulating hormone)
Which congenital condition is associated with adrenocortical failure?
Congenital adrenal hyperplasia
What are the consequences of adrenocortical failure?
1) Fall in blood pressure (hypotension)
2) Loss of salt in the urine (hyponatremia)
3) Increased plasma potassium (hyperkalaemia)
4) Fall in glucose due to glucocorticoid deficiency (Hypoglycaemia)
5) High ACTH resulting in increased pigmentation
Which adrenal hormones are predominantly insufficient in primary adrenocortical failure?
Aldosterone and cortisol
Where is pro-opio melanocortin synthesised?
Synthesised within the pituitary gland.
What are the peptides that are formed from the cleavage of POMC?
ACTH, MSH, endorphins and enkephalins
What clinical investigations are conducted for a patient suspected with Addison’s?
9am cortisol = low
ACTH = High
Short synACTHen test to measure the cortisol response (low response)
What is a synACThen test?
ACTH is administered to patients through intramuscular injections (250ug), and the cortisol response is measured.
At what time is cortisol level usually elevated?
9am
What type of injections are administered during an synACTHen test?
Intramuscular injections
What pharmacological treatment is available for primary adrenocortical failure?
Fludrocortisone 50-100mg daily
Which atom is added to fludrocortisone?
Fluorine
What pharmacodynamic effect does fluorine have in fludrocortisone?
Fluorine does not exist in natural steroids, so its presence slows metabolism substantially. Binds to both mineralocorticoid and glucocorticoid receptors.
Has a longer half life (3.5h and effects seen for 18h)