Adrenal Insuficiency and Addison's Disease

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Tests

A patient presenting with non-specific symptoms, such as tiredness and nausea, will have a blood sample taken for a general biochemical and haematological screen plus some hormone tests.

Cortisol may be requested when Addison’s disease is suspected but this alone may be unhelpful. If the cortisol result is inappropriately low it suggests adrenal failure. Cortisol can then be measured as part of a stimulation test to clarify the diagnosis.

ACTH (Adrenocorticotrophic Hormone) may be requested in Addison's disease where the concentration of this hormone in the bloodstream are usually high. In such patients a synacthen test (stimulation test) should be carried out.

Synacthen is a drug which has the actions of ACTH , the hormone produced by the pituitary gland. Synacthen is given to stimulate the adrenal glands to produce cortisol. A blood sample is taken to measure the unstimulated (before the synacthen is given) cortisol concentration and sometimes aldosterone and plasma renin activity. Synacthen is then given by injection. After 30 minutes another blood sample is taken to see if cortisol and aldosterone levels have increased. A further sample at 60 minutes is sometimes also taken (usually in children). In Addison’s disease cortisol and aldosterone levels do not increase following the administration of synacthen.

Plasma renin is a substance in the blood that stimulates aldosterone release from the adrenal and will be high in patients with Addison’s disease.

Electrolytes (e.g. sodium, potassium) are routinely measured and a low sodium and high potassium concentration together with hypotension is suggestive of adrenal hypofunction.

Glucose , urea and creatinine are measured to examine glucose levels (‘blood sugar’), kidney function and hydration status. Along with the measurement of electrolytes, these are used to monitor the response to treatment.

Adrenal antibodies are sometimes requested as part of the diagnostic process when autoimmune Addison’s disease is suspected. A positive result is helpful in the diagnosis of autoimmune Addison's disease but many patients with this form of the disease have a negative result.

Non-laboratory tests

X-rays may be used to see if the adrenal glands have accumulated any calcium deposits that can occur with a tuberculosis infection.

CT (computerised tomography) or MRI (magnetic resonance imaging) scans, are used to look at the size and shape of the adrenal glands and the pituitary. The adrenal glands can be enlarged with infections and cancers. With autoimmune diseases the adrenal glands are often normal or small in size

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