Cortisol Flashcards
When is a cortisol test run? What are the normal values?
Performed on patients suspected to have hyper- or hypofunctioning adrenal glands
Normal:
8 AM 5-23 mcg/dL
4 PM 3-13 mcg/dL
Describe the pathway from the hypothalmus to the release of cortisol
Corticotropin releasing hormone (CRH) is made in the hypothalamus. This stimulates adrenocorticotropic hormone (ACTH) production in the anterior pituitary gland, which stimulates the adrenal cortex to produce cortisol.
How does rising Cortisol affect the production of CRH and ACTH
Increased cortisol acts as an inhibitor to stop further production of CRH and ACTH.
Negative feedback loop
What is the function of cortisol in the body?
Cortisol is a glucocorticoid released from the adrenal cortex that affects metabolism of carbohydrates, proteins, and fats and increases glucose by stimulating gluconeogenesis from glucose stores.
It also inhibits effects of insulin and inhibits glucose transport into cells
Cortisol feedback visualization
Whats one of the earliest sign of adrenal hyperfunction?
The loss of diurnal variation without elevated cortisol levels yet.
Normally cortisol levels rise and fall during the day (diurnal variation) with peak levels at 6-8 AM and a gradual decrease during the day and lowest levels around midnight.
What do high Cortisol levels indicate?
High levels of cortisol indicate Cushing syndrome
What do low levels of Cortisol indicate?
low levels suggest Addison disease
In order to check whether or not cortisol levels are changing throughout the day, what times should you draw blood?
Collect blood at 8AM and again at 4 PM – the 4 PM value should be between 1/3 and 2/3 of the 8 AM value
Interfering factors of cortisol
Pregnancy has increased levels
Physical and emotional stress can elevate cortisol – stress stimulates the pituitary gland
Drugs that cause increased levels include amphetamines, cortisone, estrogen, oral contraceptives, and spironolactone
Drugs that decrease levels include androgens, exogenous steroids, lithium, and phenytoin
Causes of increased Cortisol
Cushing disease, ectopic ACTH producing tumors, stress – ACTH overproduced so cortisol rises
Cushing syndrome (adrenal adenoma or carcinoma) – neoplasm produces cortisol without regard to normal feedback mechanism
Hyperthyroidism – metabolic rate is increased so cortisol levels rise to maintain elevated glucose needs
Obesity – all sterols are increased in the obese
Causes of decreased Cortisol
Adrenal hyperplasia – congenital absence of enzymes used in synthesis of cortisol
Addison disease – hypofunctioning adrenal gland
Hypopituitarism – ACTH not produced by pituitary gland, which is destroyed by disease, neoplasm, or ischemia
Hypothyroidism – normal cortisol levels not required to maintain reduced metabolic rate.
What is Cushing disease?
A type of Cushing syndrome (too much cortisol) caused by the pituitary gland secreting too much ACTH
What is Cushing syndrome?
The body makes too much cortisol. The adrenal gland may have a tumor that secretes too much cortisol
What is Addisons disease?
A hypofunctioning adrenal gland
