ACTH Stimulation Test Results. Help!

[Charbt]

As a background, I have Hashimoto's Thyroiditis, for which I just began treatment. A few weeks ago, prior to treatment, I had an ACTH Stimulation Test run, the results of which are as follows:

Cortisol Basal 19.6 ug/dL
Cortisol Reference Range: AM = 3.4-26.9, PM = 0.9-15.8
Cortisol 30 min 26.7
Cortisol 60 min 21.2

Please note, this test was started at around 9:30-10:00 a.m. However, what does these results mean, if anything?  I've heard that upon stimulation, your Cortisol level is supposed to double, which mine did not.  Is that true?

[Red_Star]

I found a great website that i'll send through.  Based on your results, primary adrenal insufficiency would be the most likely diagnosis. There is still the possibility of Addison's disease.  It is stated that if serum cortisol level is more than 400 nmol/L (14.49ug/dl), then the diagnosis of Addison's disease is unlikely.  Some experts recommend a cutoff of 500 nmol/L (18.12 ug/dl) to exclude Addison's disease. However, it is also stated serum cortisol values are not reliable as they increase during illness.

"The Addison's Clinical Advisory Panel state that if a person is unwell, the diagnosis of adrenal insufficiency cannot be excluded by a serum cortisol level [Wass et al, 2009]. CKS therefore recommends seeking specialist advice in this situation."

To add, Polyglandular Autoimmune Syndrome Type II (PGA-II) is characterized by Addison disease in combination with Hashimoto's Thyroiditis and/or type 1 diabetes mellitus.

[rumpled]

Your doc may or may not call you AI since you started in normal and stayed in normal. Yes, it is supposed to double (or depending, hit a certain number in the 30's which you did not either). so there is a lot of room for interpretation and sometimes I have seen that the docs will go by the *normal* only... which can leave you in a sorry state.

I have Hashimoto's too - had Cushing's etc. I asked my doc - the only relation is that one auto-immune disease makes you more prone to having others...

[Charbt]

I apologize, but I have one last question.  Would high plasma renin and low plasma aldosterone confirm a diagnosis of primary adrenal insufficiency?

[Red_Star]

No problem. :)  Untreated or poorly treated hypothyroidism (most commonly due to Hashimoto's) does put stress the adrenal glands.  I'll send you a good link on this.

[Charbt]

Red_Star, I really appreciate your response.  Is it possible that my baseline cortisol level was elevated to a normal(ish) range due to untreated Hashimoto's Thyroiditis?

[Red_Star]

In a healthy person, the cortisol level should double from a baseline of 20 - 30 ug/dl within 60 minutes.  The baseline cortisol level in people with adrenal insufficiency is usually near 15 ug/dl and with Addisons disease it is well below 10ug/dl and will not rise more than 25%.

Based on your results, you may have primary adrenal insufficiency despite starting at a higher base cortisol level. I'm not a doctor, this is my opinion.  I gathered together all the info and made it into a more (hopefully) understandable interpretation:

Primary adrenal insufficiency:

The ACTH stimulation test does not double the low base cortisol level.  ACTH plasma will be at the top of the range or above range. Sometimes in Addison's disease, ACTH will be very high into the 1000's.

Secondary adrenal insufficiency:

The low base cortisol can double, triple, quadruple. The serum ACTH will usually be in the bottom half of the range to the very bottom, but not usually below the range.