Secondary adrenal insufficiency (SAI)
This is a form of adrenal insufficiency caused by inadequate ACTH production from the pituitary gland, leading to low cortisol, but usually, normal aldosterone levels.
The pituitary gland
The pituitary is a small pea-sized gland in your head that produces a hormone called adrenocorticotropic hormone (ACTH). This hormone tells your adrenal glands what to do (among other things).
If not enough ACTH is produced by the pituitary gland, then the adrenal glands will produce no cortisol, or just a small amount.
Many conditions affect the functioning of the pituitary gland, including;
- autoimmune disease
- pituitary tumors or infection
- bleeding in the pituitary
- genetic diseases that affect the way the pituitary gland develops or functions
- surgical removal of the pituitary to treat other conditions
- traumatic brain injury
The video below, from the Society for Endocrinology, gives an overview of the important role played by the pituitary gland.
Symptoms
As with other forms of adrenal insufficiency, symptoms will often develop gradually.
They will be typical of adrenal insufficiency and low cortisol, but as the production of aldosterone is not affected, they will not include hyperpigmentation, and usually won't include low blood pressure (hypotension) and dehydration, compared to Addison's disease (primary adrenal insufficiency).
Signs & symptoms of adrenal insufficiency
Diagnosis
- Patient medical history (e.g. pituitary gland surgery) will give strong indications of the risk of secondary adrenal insufficiency.
- MRI or CT scans may be used to look for abnormalities in the pituitary or hypothalamus areas of the brain.
- Blood tests for secondary adrenal insufficiency would NOT usually show high potassium levels, as they would for primary adrenal insufficiency (Addison's).
- Short synacthen test: This is an ACTH stimulation test. This is used to measure how well the adrenal glands are producing cortisol.
Blood levels of ACTH and cortisol are taken, usually between 8 am and 10 am, before a dose of synthetic ACTH (Synacthen) is given. Repeat bloods are taken after 30 minutes and/or 60 minutes. Low cortisol levels in the blood following the test mean that, in spite of the synthetic ACTH signalling the adrenal gland to work, they haven't produced cortisol, indicating an issue with the glands.
NB: if a patient has been taking glucocorticoid (steroid) medication for another health issue, it can influence the results. Also, the results are indicative of the adrenal gland function at that time, but are not indicative of future functioning.
Read more on adrenal insufficiency Diagnosis
Treatment
As with the other types of adrenal insufficiency, treatment is a time-critical medication regimen to replace the missing cortisol.
Sick Day Rules must be followed, and patients with secondary adrenal insufficiency are at risk of adrenal crisis, so they should carry an emergency injection kit.
Further resources
As well as ourselves, The Pituitary Foundation is another charity that supports people living with all types of Pituitary conditions, including secondary adreanl insufficiency.
