Session 9- The adrenal gland Flashcards
What hormones are secreted from the cortex
Mineralocorticosteroids- aldosterone
Glucocorticoids- cortisol
Sex steroids- testosterone
What hormones are released from the medulla
Adrenaline
Noradrenaline
Dopamine
What is Cushing syndrome
Chronic excessive exposure to cortisol
What is the external cause of Cushing
Prescribed glucocorticoids which is the most common cause
What are the endogenous causes of Cushing syndrome
- Cushing’s disease
- adrenal cushings
- Non pituitary-adrenal tumours producing ACTH
What is cushings disease
Benign pituitary adenoma secreting ACTH
What is adrenal cushings
Excess cortisol produced by adrenal tumour
What are the signs and symptoms of cushings
- Plethoic
- moon shaped face
- abdominal obesity
- purple striae
- acute weight gain
- hyperglycaemia
- hypertension
What is the main steroid drug used
Prednisolone- synthetic glucocorticoid
What is prednisolone used to treat
ed to treat inflammatory disorders e.g. • Asthma • Inflammatory bowel disease • Rheumatoid arthritis • Other auto-immune conditions
What are the net effects of glucocorticoids
Increased glucose production
Breakdown of protein
Redistribution of fat
What are the consequences of redistribution of fat
Higher levels of fat in abdomen
Supraclavicular fat pads
Dorsocervicual fat pads- buffalo hump
Moon face
How do you distinguish between the different causes of raised cortisol
If there’s elevated ACTH- thus indicates a ACTH dependant cause- then do a Dexamthasone test
- if suppressed- cushings disease
- if not- ectopic tumours producing ACTH
If there’s suppressed ACTH- ACTH independent- ask if they take glucocorticoids if yes- exogenous cushings, if no- excess cortisol produced by adrenal tumour
What is addisonians crisis
Life threatening emergency due to adrenal insufficiency
What triggers addisononian crisis
- Severe stress
- Salt depravation
- Infection
- Trauma
- Cold exposure
- Over exertion
- Abrupt steroid drug
Treatment of addisonian crisis
Fluid replacement and cortisol
Symptoms of addisonian
Nausea Vomiting Pyrexia Hypotension Vascular collapse
What is produced in the zona glomerulosa
Salt
Mineralcorticosteroids- aldosterone
What is produced in the zona fasciculata
Glucocorticoids - cortisol
Cortisone
Sugar
What is produced in the zona reticularis
Glucocorticoids and small amounts of androgens
-dehydroepiandrosteone
-androstenedione which is converted to testosterone and oestrogen
Sex
Order of layers of adrenal cortex
GFR
Glomerulosa
Zona fasiculata
Reticularis
What are steroid hormones produced from
Cholesterol
Lipi soluble
How to steroid hormones interact
Bind to receptors of the nuclear receptor family to modulate gene transcription
- glucocorticoids
- mineralocorticoids
- androgens
- oestrogen
- progestins
How do corticosteroids exert their actions
They regulate gene transcription
- they readily diffuse across plasma membrane and bind to glucocorticoids receptors.
- binding causes dissociation of chaperone proteins
- receptor ligand complex translocates to nucleus
- dimerisation with other receptors can occur
What is the carrier protein for aldosterone
Serum albumin and to a lesser extent transcortin
What is the role of aldosterone
It promotes expression of the Na/K pump in the collecting ducts and distal tubules of the nephron which promotes reabsorption of Na+ and excretion of K+ thereby influencing water retention, blood volume and therefore blood pressure
How can you distinguish between primary and secondary hyperaldosteronism
Primary- low renin high aldosterone:renin ratio
Secondary -high renin low aldosterone:renin ratio
What is primary hyperaldoseronism
Defect in adrenal cortex
What can cause primary hyperaldosteronism
Bilateral idiopathic adrenal hyperplasia
Aldosterone secreting adrenal adenoma - Conn’s syndrome
What is secondary hyperaldosteronism
Due to over activity of RAAS
What an cause secondary hyperaldosteronism
Renin producing tumour-rare
Renal artery stenosis
Signs of hyperaldosteronism
High BP
Left ventricular hypertrophy
Stroke
Hypernatraemia
Hypokalaemis
Carrier protein in plasma for cortisol
Transcortin
Actions of cortisol
Increased proteolysis in muscle Increased lipolysis Increased gluconeogeneis in liver Resistance to stress Anti-inflammatory effects Depression of immune system
What is Addison’s disease
Chronic adrenal insufficiency
Destructive atrophy from autoimmune response
Signs and symptoms of addisons
Postural hypertension
Lethargy
Weight loss
Anorexia
Increased skin pigmentation
Hypoglycaemia
Why does Addisons cause hyperpigmentation
Decreased cortisol
Negative feedback on ant pituitary
More POMC required to synthesis ACTH
POMC is used to make MSH therefore more melanin
ACTH itself can also activate melanocortin receptors so melanocytes will also contribute
What receptors in the heart increase heart rate and contractility
Beta 1
Wha receptors cause bronchodilation
B2
What receptors cause vasoconstriction in blood vessels in tthe skin and gut
A1
What receptors cause vasodilation in blood vessels in skeletal muscle
B2
What is phaechromocytoma
Chromaffin cell tumour - rare catecholamine secreting tumour - mainly noradrenaline
Phaeo-dark
Chromo-colour
Cyte-cell
Oma-tumour
symptoms of phaeochromocytoma
Severe hypertension
Headaches
Palpitations
Diaphoresis
Anxiety
Weight loss
Elevated blood glucose
What is the difference between cushings disease and syndrome
Cushing’s syndrome refers to the general constellation of symptoms resulting from chronic excessive exposure to cortisol whereas Cushing’s disease refers to the specific case of a benign ACTH secreting pituitary adenoma. Cushing’s syndrome is much more common than Cushing’s disease.
How do you investigate adrenocortical function- cushings
Measure plasma cortisol and ACTH levels and 24hr urinary excretion of cortisol and its breakdown products
Dexamthasone suppression test and ACTH stimulation test
What is Dexamthasone test
Dexamthasone is a Potent synthetic steroid that when given orally will suppress the secretion of ACTH and then therefore cortisol
Suppression dozens occur in adrenal tumours or ectopic ACTH production
How would you investigate Addison’s disease
Administration of synacthen- synthetic analogue of ACTH- intramuscularly which would normally increase plans cortisol. If normal excludes Addison
