Question: When getting tested for Cushings, does a recent cortisone shot (two weeks prior to the initial test) affect the outcome? If so, how?

Answer: Cortisone can affect steroid testing in several ways. First, cortisone may be detected in steroid assays, so, if administered within about 24 hours, the cortisone injection could result in an artificially high serum value. A shot two weeks prior should not affect the results therefore. In addition, cortisone administration could also lead to a dampening of pituitary ACTH secretion, leading to lower production of cortisol by the adrenal glands. This is an important clinical issue largely when we are trying to assess whether patients may have adrenal insufficiency (low amounts of steroid), as levels may be on the low side and it may be hard to distinguish true adrenal insufficiency from a temporary effect due to the recent steroid use. In a patient with Cushing’s syndrome due to excessive secretion of ACTH, such as from a pituitary tumor, a single shot of steroids a few weeks before should not affect testing.

By Dr. Laurence Katznelson MD (Spring, 2008)