Baselines & The Day Curve Test

When you’re diagnosed with Adrenal Insufficiency, you’re given a ‘baseline dose’ of steroids to take every day, which replaces the stress hormone, cortisol, (natural steroid) usually made by the adrenal glands. It’s called a baseline because that’s the minimum amount, you can increase it in certain situations, called a ‘stress dose’. There isn’t a set amount of cortisol which should be replaced though- some people are more anxious or stressed in general, which would mean they’d have a higher level of cortisol. Other environmental factors, such as your daily level of activity and metabolism rates also have an impact. 

So it’s not as simple as ‘take the medicine’ and you’ll be able to manage it, it’s closer to asking a diabetic to administer insulin without checking their blood sugar first. Diabetics have to check their levels many times a day to get it right, but with cortisol, there’s currently no way of checking because a testing metre doesn’t exist. 

To check if your baseline dose is suitable for you and you have adequate coverage of cortisol, the U.K. offers a ‘Day Curve Test’. You have to collect all of your urine for 24 hours and take it to the hospital the next day, and then your bloods are taken and tested at varying points through the day, usually 8am-6pm. Other countries don’t have this test, so it’s good we have it. The problem is, you’re sitting down at home or in a hospital for 2 days so it’s not actually an accurate assessment as to how environmental factors impact on your use of cortisol through the day. The test is supervised by an endocrine nurse. If you live near the hospital, you could leave and come back in between the blood draws. 

Ranges in the UK for cortisol are in nmol/L. A minimum ‘safe’ range starts about 150 (it depends on your hospital trust) and the maximum is about 650. Cortisol is supposed to be highest in the morning and reduce throughout the day. Your body naturally starts making cortisol at around 3am to help you get up in the morning and should ideally be 500 ish by about 8am, then it’ll decrease as the day goes on, unless you have ‘stressful’ things which will increase it again. In other countries, some people wake up at 3am to take steroid to make sure they can wake up properly at 8am (so mimicking the body more naturally), but that doesn’t seem to be a recommendation here. The times of the doses are designed to mimic the body’s natural ebbs and flows of energy, known as the Circadian Rhythm

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My baseline is 10mg of Hydrocortisone at 8.30am, 5mg at 12.30 and 5mg at 17.30. My day curve blood draws happened at 9am, 1pm and 6pm, each taking place roughly half an hour after taking my Hydrocortisone. When I did this test 18 months ago, mine came back (roughly, can’t fully remember) as: 

Morning: 370

Midday: 250

Evening: 180

This means my baseline keeps me ‘safe’ because it’s within the ranges, but it doesn’t leave me with a lot to function on. It’s a bit like running a car with no oil- you can do it, but it’ll splutter and stop at a random point and probably overheat (I also have ‘meltdowns’). It was done when I wasn’t walking or moving, I didn’t have any underlying illness and I wasn’t emotionally stressed that day- so if I sit still I’ll survive, anything more than that and we don’t actually know, it’s back to guessing! Really random things use up cortisol, which you can read about here. 

There are a few options in terms of steroids you can take. The most common ones tend to be Hydrocortisone taken at points throughout the day, or Prednisolone, taken in the morning (usually, it can differ). This is because HC lasts roughly 4-6 hours whereas Pred lasts much longer. I tried one off Pred dosing and it didn’t work for me. This is another area we struggle with as patients- the treatments haven’t really been updated since the 1970s and the general feeling among British patients is that we’re a lot more restricted or offered less diverse treatments than in other countries, where there’s slightly more research into the condition. But at least we have the Day Curve Test!

It’s really interesting how the body works though. I know when it’s nearly ‘hydrocortisone time’ because I really struggle to function about an hour before, so I tend to avoid doing things or interacting with people at these times because I’m not very coherent or coordinated. The person who discovered cortisol said it was like watching Lazarus rising from the dead- their patient was on death’s door but was up and eating and chatting following an injection of cortisol. When I take it, I can feel the heaviness, fogginess and pressure lift a bit. For me, my baseline is my lifeline and I would die pretty quickly without it, but there’s also a noticeable difference in how I feel when I take it. 

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