HPA Axis: Clinical Aspects Flashcards
What types of hormones does the adrenal cortex produce?
- Glucocorticoids (e.g. cortisol)
- Mineralocorticoids (e.g. aldosterone)
- Sex steroids (androgens)
What binding protein does the majority of cortisol bind to?
Cortisol binding globulin (90%)
How do cortisol levels vary throughout the day?
Cortisol levels rise in the morning and peak just before waking up.
They then fall during the day and are low in the evenings.
This is known as circadian rhythm (levels oscillate over 24 hours)
What do mineralocorticoid receptors have the same affinity for?
Aldosterone and Cortisol
How do the kidneys ensure that the majority of mineralocorticoid receptors bind with aldosterone and not cortisol?
They contain 11-B-HSD-2 enzymes which inactivates cortisol into cortisone, meaning there is less cortisol available to compete with aldosterone.
What is Cushing’s Syndrome?
A metabolic disorder caused by having too much cortisol
What can Cushing’s syndrome lead to?
- Hypertension
- Weight gain (central obesity so not arms or legs)
- Insulin resistance
- Osteoporosis
What can cause the excess cortisol levels that leads to Cushing’s syndrome?
- Pituitary adenoma (affecting corticotrophe cells)
- Adrenal tumour (adenoma)
- Steroid treatment
What are some clinical features of Cushing’s syndrome?
- Central obesity
- Rounded face
- Thin skin (easily bruised)
- Hirsutism
- Diabetes
- Hypertension
- Osteoporosis
- Psychiatric problems
What is Addison’s disease?
Having too little cortisol and it is usually autoimmune
What are some clinical features of Addison’s disease?
- Malaise (general discomfort/pain)
- Weakness
- Weight loss
- Hypotension
- Hypoglycaemia
Why should you never investigate for an endocrine condition in a patient unless their signs/symptoms suggest they have it?
Due to the risk of a false-positive
When should you image an endocrine gland?
After a diagnosis has been made biochemically
When is the only time you need to image patients with Addison’s disease?
When you are concerned that they may have TB or cancer
How can Addison’s disease be managed?
Steroid hormone replacement therapy (glucocorticoid) and sometimes mineralocorticoids will be needed too.
