L6 Adrenal Glands Flashcards
Where are the adrenal glands located?
Pyramid shaped structure above each kidney.
Describe the structure of the adrenal glands.
- Gland enclosed in a fibrous capsule
- Adrenal medulla (inner layer)
- Adrenal cortex (3 layers)
- Rich blood supply directly from the aorta
Which structures are in control of the medulla and cortex?
- Cortex is under the control of the anterior pituitary gland
- Medulla is not under hormonal control and is therefore not a true endocrine gland
Describe the structure of the adrenal medulla.
- Modified part of the symapthetic nervous system
- Inner layer of the gland
- Contains chromaffin cells which release adrenaline and noradrenaline when depolarised
What hormones are secreted from the adrenal medulla?
Secretes catecholamine hormones:
- Adrenaline (80%)
- Noradrenaline (20%)
What are the functions of catecholamines?
Prepares the body for acute stress (fight or flight).
Increase blood pressure, bladder weakness, increased heart rate, dry mouth, light headedness, sweating.
What are the cardiovascular effects of adrenaline?
- Increased heart rate and stroke volume
- Increased systolic blood pressure
- Vasodilation of coronary and skeletal muscle BVs
- Vasoconstriction of BVs to non-essential tissues e.g. GI tract, skin, kidneys
- Bronchodilation to increase oxygen uptake
What are the metabolic effects of adrenaline?
- Metabolic rate increases
- Liver converts glycogen to glucose
- Increased energy for immediate use
- Blood flow changes, reduces digestive system activity and urine output
What are beta blockers?
Drugs which suppress the action of adrenaline by blocking beta receptors, used to treat hypertension.
What is the main function of the adrenal cortex and its hormones?
To deal with long-term stress e.g. exam anxiety.
What are the 3 zones of the adrenal cortex?
- Zona Reticularis (inner): produces gondocorticoids (androgens)
- Zona Fasciculata: produces glucocorticoids (cortisol) to control BGL
- Zona Glomerulosa (outer): produces mineralocorticoids (aldosterone) to control sodium
What type of hormones are secreted by the adrenal cortex?
Steroid hormones
What causes the 3 zones of the cortex to be distinct from eachother?
- Same cell types but different enzyme types present
What is the starting molecule for all steroid hormones?
Cholesterol
Describe androgen production.
- Adrenal cortex is stimulated by ACTH from the anterior pituitary
- Causes dehydroepiandosterone (DHEA) and (DHEA-S) production
- These are precursors to testoserone, converted to testosterone in peripheral tissues
What are the effects of excessive adrenal androgens?
- Masculinisation of women
- Breast shrinkage, acne, irregular periods, facial hair
- Plays a role in PCOS
- Caused by ACTH overproduction
- Treated with cyproterone acetate to block andorgen receptors
Describe the effects of testosterone in men and women.
Men:
- No identifiable function of adrenal andorgens as the testes already produce significant amounts of testosterone
- Possible link with aggression in young boys
Women:
- Kick starts puberty
- Responsible for pubic hair growth and sex drive
How is aldosterone produced?
- A mineralocorticoid
- Secretion is regulated by plasma levels of sodium and potassium via the renin-angiotensin system (RAAS)
- Renin secreted when sodium in distal tubule is low
- Renin converts angiotensinogen to angiotensin I
- ACE (angiotensin converting enzyme) converts angiotensin I to angiotensin II
- Angiotensin II stimulates aldosterone secretion in the adrenal cortex
What is the function of aldosterone?
- Conserves sodium when sodium is low and plasma potassium is high
- Retains/increases blood volume
What is cortisol?
A glucocorticoid, production stimulated by stress.
When are cortisol levels highest?
At the start of the day, lowest at night.
What are the metabolic actions of cortisol?
Metabolic effects:
- Increases skeletal muscle catabolism, converts AAs to glucose
- Increases lipolysis for energy source
- Stimulates appetite
Cortisol causes fat stores and excess circulating fat to be relocated and deposited deep in the face and abdomen.
What are the other functions of cortisol (non-metabolic)?
- Anti-inflammatory actions
- Immunosuppressive actions
- Increases BGL
- Can contirbute to emotional instability
How is cortisol produced?
- Hypothalamus releases corticotrophin releasing hormone (CRH) to the anterior pituitary
- Anterior pituitary releases adrenocorticotrophic hormone (ACTH) to the adrenal cortex
- Adrenal cortex secretes cortisol
Give 3 examples of adrenal cortex hyperfunction.
- Cushing’s syndrome
- Conn’s disease
- PCOS
What is Cushing’s syndrome?
- Excess cortisol
- Can be caused by taking steroid hormones, or an adrenal or pituitary tumour
- Muscle wastage, hypertension, hyperglycaemia, fat redistributed to face and abdomen
What is Conn’s disease?
- Rare
- Excess mineral corticoids
- Excess aldosterone
- Retention of sodium, loss of potassium
- Causes hypertension due to increased plasma volume
What is PCOS?
- Overproduction of adrenal androgens
- Facial hair in women
Give an example of adrenal cortex hypofunction.
Addison’s disease:
- Rare
- Excess ACTH
- Low cortisol, androgens and mineralocorticoids
- Damage to adrenal or pituitary glands
- Pigmentation of mucosal membranes (e.g. gingivae)
- Progressive weakness, weight loss, lassitude
Why are steroid hormones important in dentistry?
- If a patient is on long-term systemic steroid medication they should recieve supplementary glucocorticoids when undergoing stressful treatement (i.e. dental procedures)
- Treat patients on steroids earlier in the day when cortisol is highest
