Addisons tests and biotin interference

[Opal79]

Hi I'm hypothyroid, currently on 112mcg levo which hasn't really hekped, plus Pernicious Anaemia which i self inject every othrr day B12.

I had a cortisol test back in mid august as I suspected cushings, it was 86nmol/L so instead very likely Addisons /AI. This was via my private endo who was about to start me on T3 for my hypothyroidism (i dont convert FT4 to FT3) and so hasn't yet due to this, and arranged an SST instead.

I had to go to NHS for this in the end as I've major allergies and needed to be in setting near A&E, so my GP did another cortisol test in order to get me referred on NHS. But it was 323 nmol/L.

Amazingly nhs endo accepted it based on the 86 reading, but the difference in both test results was biotin! I'd been off it for 2 months prior to test that was 86 (as on a b12 injection protocol for my P.A) but back on it for a month when I took the 2nd test of 323.

I've read you should stop biotin 6 weeks before testing for true cortisol reading and my SST is booked for 17th Oct - only 3.5 weeks after stopping biotin again.

I'm scared it'll affect the reading again as this is my only chance of diagnosis - and they only do ACTH if cortisol is low enough that day i think? (I could be secondary as take Qvar asthma inhalers so really want ACTH, equally though I have hashi and P.A so could be primary).

But I just feel so so ill and getting the brick on my head and waking up is getting so bad in mornings, and I'm so scared of crisis. I also have a hydrocortisone allergy so believe I'd need prednisolone treatment instead, but in an emergency not sure if A&E would listen!

No idea what to do for the best, so just incase anyone could advise please I'd be so so grateful. Thankyou 🙏

[radd]

Opal79,

Goodness you have a lot going on. Poor you.

You are ok re your stim test as it's six weeks to stop oestrogen-containing medications (including contraceptive pill/HRT) prior because it risks inducing cortisol binding globulin.

It's only a few days for biotin (some papers say 2-4, some say 3-5), the same as when we stop biotin for thyroid hormone testing because it can effect a multitude of hormones. The problem is huge amounts of biotin can interfere with the biotin-streptavidin system used in many immunoassays, adversely producing a false high in some and a false low in others.

However, ensure your consultant knows you are using asthma inhalers because depending on your dose, this can suppress cortisol secretion.

[Opal79 in reply to radd]

Hi Radd thank you so much for your reply. I've been abit confused because a mod in an addisons online group said about it being 6 weeks for both oestrogen and cortisol. She showed me an ncbi document on this, but it doesn't say 6 weeks for biotin anywhere, and like you've said it says about high doses like 5mg upwards. I've been taking 300mcg in my b complex so not too much?

When I queried her about the 6 weeks she said its generally recognised for biotin too and said to look at google scholar but I can't find anything about actual time off it.

She had also previously advised me to take the 2nd test (that was 323) even though I'd been back in biotin a month since the test of 86, but off it one day - and said if I was that low in first teat it would have to rise alot to look normal.But of course it did and I'm amazed the endo would see me so early to be honest.

I asked the endo nurse recently and she said maybe my test of 86 was a false reading? I feel so ill so I doubt it tbh! Thanks I did tell them about my asthma and steroid inhalers as well as all my allergies, I'll come off inhalers 16 hours before test.

Just not sure who to trust really, this mod says go for the 17th Oct anyway even though only 3.5 weeks off biotin, so I've been worried her advice will not succeed again and I'll be left without diagnosis or treatment.

I don't supoose you have any accredited links for papers etc you could send at all please about it being a few days off biotin? I'm really so confused by the whole thing in my foggy state! No worries if not, and I appreciate your reply , thanks so much 😊