Thyroid UK
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Suspected Cushing's: High cortisol levels on saliva test, now low cortisol after 8 months on Levothyroxine. Can this happen with Cushing's?

Hi all. For a number of years I've been increasingly ill and earlier this year a doctor suggested I be checked for Cushing's as I have many of the primary symptoms, including huge weight gain around my stomach (despite genuinely eating little food due to nausea), the stria (reddish purple stretch marks) around my stomach and the so called buffalo hump on my upper back which has caused me to lose almost 3 inches in height over a period of time.

Private saliva tests showed raised cortisol earlier this year at the peak of bright red flushing in my face, but it was also found my TSH level was too high. So, my GP put me on 50 micrograms a day of Levothyroxine. I actually stressed to him I was unsure it was wise to start messing with my hormone levels before I had testing for Cushing's. Please appreciate I obviously don't want to have Cushing's (nobody does!) but I have become so ill I was somewhat hoping a series of 24 hour urine collections plus the overnight dexamethasone test would finally give me an answer and some hope of finally being treated. Therefore, it's to my horror and despair that results have come back showing my cortisol levels to be far too low, resulting in me having a brief Synacthen test (results pending).

My primary question is this: has anyone on here been ultimately been diagnosed with Cushing's but suffered similar results after being (seemingly wrongly?!) prescribed daily Levothyroxine... i.e. this tablet has caused the adrenal glands to somewhat stop producing the cortisol?

I did note, moments after being injected with cortisol, I started to suffer the very same symptoms I had when the saliva tests showed high levels of cortisol: this being an overwhelmingly strong sensation of warmth throughout my face. I had believed this uncomfortable sensation had only recently stopped happening as much when inactive because I've quit work and have tried to feel more relaxed. On stopping Levothyroxine five days ago, this very same, seriously uncomfortable flushing in my face has returned.

Any advice or knowledge regards the impact of Levothyroxine (the same as Thyroxine?) Would be greatly appreciated as I'm fearing consultants will see my cortisol levels have gone from around 92 around 7 months after first taking Levothyroxine to, perhaps, a number more like the acceptable average as I've only been off the Levothyroxine five days before the synacthen test. I hope the majority of endocrinologists will accept that an error was made in prescribing this to a possible Cushing's suffer and not simply tell me to go on my way without further 24 hour urine and dexamethasone testing as I feel currently as if the ignorance of a local GP in prescribing Levothyroxine has potentially blown my chance of finally becoming better. Before taking Levothyroxine I was told by different consultants that my body image and symptoms are "screaming" Cushing's. I'm quite simply desperate for hope and reassurance that one tablet hasn't wiped out my main chance of ending this nightmare illness now I've had recently had repeatedly negative urine tests for Cushing's (this was when I didn't appreciate the impact of Levothyroxine and therefore did not highlight it to endocrinologist except for including it on my medication lists).

Apologies for the length of this and thanks in advance for any responses.

Sending kind regards and best wishes to you all. Thank you.

11 Replies

I'm no expert, and not medically trained, or anything, but I don't think levo does that. It would be a god-sent to people with high cortisol if it did! People with high cortisol - not Cushing's, just high cortisol - find they cannot lower it.

And your doctor did not prescribe levo (thyroxine, levothyroxine, all the same thing) because of your high cortisol, but because of your high TSH. Two different things. If your TSH is high, then it's your thyroid gland that is failing, not your adrenals.

My apologies if that was not what you were asking and if I misunderstood your question.

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Hi greygoose,

Thank you so much for your reply as you've certainly helped me understand this more than I previously did.

I've been belatedly concerned about my use of Levothyroxine as, after discovering my cortisol levels had gone too low, rather than too high, I did read that this medication can cause problems in a person with as-yet undiagnosed and untreated Cushing's - or any Adrenal issue - and so I'm genuinely interested to know if anyone has either heard of or personally suffered such a turnaround in results as going from too high to too low levels of Cortisol. My understanding is that prolonged exposure to excess cortisol can provoke something akin to a burn out in the adrenals, resulting in the severe drop in cortisol levels and that this can be provoked by Levothyroxine.

Anyway, again, I really appreciate you taking the time to reply, especially as I know from my own extensive (but often frustratingly contradictory) research that Cushing's can be a huge challenge to get confirmed, let alone treated.

Take care and sincere thanks again.


Well, I think it's rather rare, so the odds of finding someone on here that's been through the same thing, are pretty low. But a lot more people will read your post tomorrow, so don't despair! :)

I've never read much about Cushing's, so I didn't know that. But, if it's true, an endo will know it. All you have to do is tell him that you took levo, and he'll understand. Best to tell them things out loud, they only skim through your notes and could miss things like that.


Your comment about consultants skimming notes made me smile and think: "Ah, there speaks someone who knows!" 😱☺️

Sleep well and a big thank you again.



Thank you, and you're welcome. Sleep well, too.


I'm not clear on one thing...

You had a private saliva test showing high cortisol. You also had another test showing lower or low cortisol.

Was the second test a saliva test or a blood test?

The reason I ask is that the saliva and blood tests don't measure the same thing. Hormones (and other substances) can be moved around the body bound to carrier proteins. Hormones which are bound in this way can't be directly used by the body. Some process has to happen first to separate the hormone from the carrier protein.

If you have come across the idea of thyroid hormones being measured as Total T3 or Free T3, or Total T4 or Free T4 it is exactly the same idea. The Free hormones (unbound hormones) are the one the body can use.

Saliva testing for cortisol measures unbound cortisol. Blood testing measures bound cortisol. Being high in one and low in the other (or vice versa) is not particularly uncommon.

Sorry if this is all a bit vague - I have no medical training.

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Hello humanbean. No need to apologise as any and all advice and information is really welcome, so thanks for explaining this to me.

Regards the differing results: the privately paid for saliva tests for cortisol levels showed very high levels across the 4 samples I collected over 24 hours.

Around 4 months later (and by now I'd been taking levothyroxine for around 3 months) I had the dexamethasone test for which I took a tablet at 11pm the night before for a blood sample taken at 9am by an NHS nurse.

At around 5 months after starting Levothyroxine I did many consecutive 24 hour urine collections. I had noticed the severe flushing experienced when I did the saliva tests was nowhere near as bad by now, but I thought it was simply because I was no longer overly stressed by work (as even a tiny bit of stress was causing very severe flushing, night sweats, pain etc etc). I think everyone who has seen me (family and consultants alike) have been shocked by recent results showing my cortisol levels to now be worryingly low as even I acknowledge I look like a walking advert for Cushing's.

Apologies for my lengthy reply but I wanted to ensure I got back to you after you kindly took time and effort to answer me. Sincere thanks again. I hope I made some kind of sense of this perplexing situation.


t4 meds didnt lower my cortisol so i think the testing not being the same is hard to compare...


That's interesting to know, so thanks for your reply jacrjacr.


Hi can I suggest you have a look at the pituitary foundation website and then maybe contact the endocrine nurse on the hot line ( I think it is run three time a week) , she is a lovely lady and very well informed. They also have some very good literature .

I have ( or had ) Cushings disease caused by a pituitary tumour, but diagnosis took a while. Even though I had all the classic symptoms, moon face, buffalo hump, high blood pressure , bruising , truncal obesity etc etc, and they were sure it was Cushing's results and tests did not confirm it immediately . They reckon mine was possibly cyclical Cushing's which complicated things a bit ,so some 24 HR urines came back low and others high. In the end I got admitted for a week and they did a whole battery of tests to decide what was going on.

It is also possible to have ACTH producing tumours on the adrenals or ectopic rather than the pituitary -that can alter things too.

So maybe give Alison a call, I have found her to be very supportive- she can talk you through test results , point you in the right direction or just be just someone to listen.

All the best

R x

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Hello Ratkinson :) Thank you so very much for your detailed help and support. That's so good of you, thank you! I'm genuinely sorry you've likely been through similar as, believe me, I know the suffering and all the snowball effect of being ill without diagnosis. I hope you're much recovered and looking towards a brighter future. I've got to the stage I just want to get diagnosed and finally get help as its just torture.

I'll definitely phone Alison and fingers crossed she can help. Thank you!!!!!!

Have a lovely weekend.


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