T1 L6, The Adrenal cortex Flashcards
Which part of the adrenal gland is essential for life?
The functioning adrenal cortex
Which is the outer layer of the adrenal cortex?
The zona Glomerulosa
Which is the middle layer of the adrenal cortex?
The zona Fasciculata
Which is the innermost layer of the adrenal cortex?
The zona Reticularis
In which adrenal cortex layers is the enzyme 17a-hydroxylase present?
The zona Fasciculata and zona Reticularis
In which adrenal cortex layer is cortisol synthesised?
In the zona Fasciculata
In which adrenal cortex layer are androgens synthesised?
In the zona Reticularis
How is glucocorticoid secretion controlled?
By a feedback loop and cortisol acting as that messenger
The hypothalamus releases CRH which stimulates the anterior pituitary gland to release ACTH which stimulates the adrenal cortex to release cortisol. The Cortisol will then signal to the hypothalamus
Describe the secretion of ACTH throughout the day
The peak is in the early morning and lowest in the middle of the night
There is increased secretion during prolonged stress
Describe the secretion of ACTHB throughout the day
The secretion pattern is similar to ACTH but the lowest and highest is about 2 hours later after the those of ACTH
What % of cortisol is free in the blood and active?
10%
How does the amount of free blood cortisol change during pregnancy?
It stays the same. There is an increase in circulating plasma but cortisol concentrations stay the same
Where are adrenal steriods metabolised?
Mainly in the liver where they are glucuronidated to form water soluble forms which can be excreted in urine
How do glucocorticoids produce their effects?
They act on intracellular receptors and alter gene expressions
At normal physiological concentrations, what is the most important action of cortisol?
It’s role in carbohydrate metabolism
What are the roles of Cortisol?
The opposite effects to insulin:
- Antagonises the effects of insulin on cellular uptake of glucose
- Stimulates glycogenolysis
- Stimulates hepatic gluconeogenesis
- Stimulates lipolysis
- potentiates the effects of growth hormone and catecholamines
- Direct effects on the brain
- Indirect effects on pain
What effects does cortisol have when it’s in excessive concentrations?
Fat synthesis and deposition in new sites Eg, face, trunk, intrascapular region
What does cortisol do in the liver?
Stimulates amino acid uptake leading to enhanced gluconeogenesis
What does cortisol do in the periphery?
It inhibits amino acid uptake and protein synthesis, resulting in a net loss of skeletal protein
Is it true that Glucocorticosteroids can also stimulate aldosterone receptors?
Yes
What does the enzyme 11beta-hydrosteroid dehydrogenase do?
It converts cortisol into inactive cortisone
At what conditions are the mineralocorticoid actions of glucocorticoids only apparent?
In high concentrations
Which hormone if in excess, can enhance vasoconstrictor responses to catecholamines which increases blood pressure?
Cortisol
Is it true that glucocorticosteroids can produce psychological effects with possible feelings of elation or sedation?
Yes
Give examples of ways that Glucocorticosteroids affect the body’s defence systems
- They supress lymphoid tissues
- Reduce antibody production
- inhibit the cellular immune system
- They stabilise leucocyte membranes and reduce the release of proteolytic enzymes
- Inhibit phospholipase A2 and reduce the synthesis of the inflammatory mediators
(They reduce inflammation)
What role do glucocorticoids have in times of prolonged stress?
They maintain the enhanced supply of glucose but also supress the inflammatory response
What role do prostaglandins have in tissue repair?
They enhance it
Why is to that steroids appear to have effects contrary to the individuals best interests?
Because they supress the immune response and the process of inflammation so they potentiate adverse effects of the injury and retard tissue repair
What are the effects of steroid-induced sedation?
It removes pain and decreases immobilisation induced by oedema so it causes a lack of awareness of the injury and its severity
How is the secretion of aldosterone directly stimulated?
By trauma, anxiety, hyperkalaemia, hyponatraemia
What inhibits aldosterone?
ANP (Atrial natriuretic peptide)
What does aldosterone do?
It stimulates reabsorption of sodium ions in the distal tubule of the kidney
What is the drug Hydro cortisone used for?
It’s cortisol and is used as a replacement for when the body doesn’t produce enough cortisol.
It taken at times when cortisol would be naturally released into the blood
What are some adverse effects of the drug Hydrocortisol?
Hyperglycaemia, Osteoporosis, Cushing’s syndrome
What are the pharmacological uses of glucocorticoids?
For inflammation
Orally - replacement or immunosuppression
Inhaled - Asthma or hayfever
Topical - Eczema
What are some adverse effects of steroid therapy?
- Suppressed wound healing or exacerbation of infection sue to immunosuppressant effects
- long term use in children can inhibit growth
- Long term use in adults can cause osteoporosis
- Development of diabetes mellitus and other symptoms of Cushings syndrome
How can long term use of glucocorticoids result in adrenal cortex atrophy?
Exogenous administration will cause suppression of ACTH secretion which causes atrophy
What happens if a patient suddenly stops steroid therapy?
The adrenal cortex is unable to secrete endogenous hormones so the patient suffers an Addisonian crisis
