Help understanding short synacthen test result

[JonnyA]

First and foremost, apologies if I’m posting this in the wrong place, but I’ve seen other helpful reasons on this forum about short synacthen tests for adrenal insufficiency, and thought it worth a shot.

Quick background, I’m 38 years old, male, and been experiencing pretty debilitating symptoms for about 6 years - fatigue, brain fog, feelings of weakness, and so on. It was identified that I had a thyroid issue a while back, and I’ve been taking T3 for about 2 years which has helped some, but not all symptoms. This has led me down the path of seeing more endocrinologists and ultimately, to taking a short synacthen test to rule out Addison’s disease / adrenal insufficiency.

On the report I received from pathology, they describe the following with regard to interpretation:

“30 minute results should show an increment over the basal value of >200 nmol/L to a level of >500 nmol/L. A nil or suppressed response may be seen in adrenal insufficiency, hypopituitarism, or prolonged steroid therapy“

Here are my results, full report below (with personal details redacted) for reference.

0 minutes cortisol - 422.9 nmol/L

30 minute cortisol - 511.2 nmol/L

Now, evidently my 30 minute result is just above the minimum threshold, however it does not rise by an incremental 200 nmol/L - just 88.3 (44% of the minimum incremental rise).

I’m unsure on a couple of fronts. Firstly, does a result of >500 nmol/L after 30 minutes completely rule out adrenal insufficiency? I ask not because it’s borderline, but because I’ve seen some NHS documentation reference 420 nmol/L as the minimum, and yet my baseline result is already slightly higher than that.

Second question is how significant is that seemingly inadequate response of 88.3 nmol/L to the synacthen? The note on the report states that “a suppressed response may be seen in adrenal insufficiency”. Could my result indicate as such?

Naturally, I intend to follow-up with my endocrinologist, however since I’m paying for this by my own steam at this point, I wanted to better understand how worthwhile this was likely to be in the first instance.

Thanks!

[greygoose]

Well, basically, as I understand it, it works like this:

You have a short synacthen test because your cortisol is low, and they're trying to find the cause: is it due to a) the adrenals themselves, b) the pituitary not producing enough stimulus to the adrenals.

So, if the adrenals react well to the injection of the stumulus, there is nothing wrong with the adrenals except that they aren't usually being stimulated enough: they are capable of producing good levels of cortisol.

But if they don't react to the stimulus then it has nothing to do with the pituitary, it's the adrenals that aren't capable of making enough cortisol. So, the question then is if it's Addison's or not. It could just be adrenal fatigue, but doctors refuse to believe adrenal fatigue exists! Although it's pretty common amongst hypos because when the thyroid starts to fail, the adrenals take up the slack and produce more cortisol. But, they can't go on doing that forever.

But, 9 months ago, you were saying that your cortisol was high, and asking the best way to decrease it. So, what happened? Why did they suspect Addison's?

And, from what I can gather, glancing back at your past posts - not time to read them all - you had primary hypo when diagnosed. So, your pituitary is unlikely to be the cause. Or did I get that wrong?

[JonnyA in reply to greygoose]

Thanks. You’re right, and this is why this is all rather confusing, that I had previously returned a cortisol saliva test that showed as high at 3 out of the 4 measurement times. I actually went to see an endocrinologist as I am experiencing persistent hypoglycaemia (as confirmed by 4 weeks with a continuous glucose monitor).

He requested a series of blood tests which confirmed I am not diabetic - in fact my insulin levels are below the bottom of the range (which apparently isn’t a problem, and is a good thing if anything). They also checked cortisol, which checking back came back as 273 nmol/L (considerably lower than my 9am baseline this time around), hence the short synacthen test.

If I read the results correctly, they appear to show adequate baseline levels, but a poor response to stimulus. I wasn’t sure if i was reading the point on expecting a >200 nmol/L rise over the basal reading correctly, but it’s written in less ambiguous terms on this NHS doc here (see “Interpretation” point #1):

leedsformulary.nhs.uk/docs/...

It’s all rather confusing. All I know is that I still feel rather ill in general and I’ve no concrete reason as to why.

[greygoose in reply to JonnyA]

Trouble is, I think doctors are pretty confused about this test, too. They don't seem to know why they're doing it, nor what the results mean.

I agree with DippyDame , it could be that you're just under-medicate for you, and need an increase in dose, due to impaired Thyroid Hormone Resistance, like me and her!

[DippyDame]

Normal values for a blood sample taken at 8 in the morning are 140 to 690 nmol/L.

Your result is 422.9 nmol/L

A cortisol of >420nmol/L at 30 minutes post Synacthen indicates an adequate adrenal response.

Your result is 511.2 nmol/L

Both readings indicate satisfactory results

For comparison, my results in 2019 were

0 mins 193 nmol/L

At 30mins 739 nmol/L

Result - satisfactory.

But bear in mind testing was likely to be at a different time of day.....level falls throughout the day

The peak level secretion occurs in the morning (07:00–08:00 a.m.), which is considered the active phase, while its lowest secretion is around 02:00–04:00 a.m.

So, normal values depend on the time of day and the clinical context. Normal ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens.

How much T3 are you taking?

On T3-only lab results are no longer reliable markers so we have to rely on good old fashioned clinical evaluation/ signs and symptoms.

Your symptoms suggest undermedication.....be that glandular in origin, or cellular.

Your thyroid journey reads very similar to my own which I've explained in my bio....it might help you to read that.

Have you optimised vit D, vit B12, folate and ferritin...all essential for good thyroid health.

Based on your medical history I would suggest you consider reading the following e-book available on Amazon for £3.56 or free if you have Amazon Prime. It is called "Impaired Sensitivity to Thyroid Hormone (Thyroid Hormone Resistance)" by Hugh A Hamilton.

I doubt you have adrenal insufficiency but I don't have a medical degree so cannot diagnose. My comments are based on my lived experience.

I hope your endo is well informed...mine wasn't!

Good luck