Fig. 1.

Main steps followed in recruiting and working with volunteers during study stage 1. Interested participants were phone screened, and if screening was positive, an initial appointment was scheduled to discuss in full detail the parameters of the study and answer any queries. During that appointment, a full screening process takes place. If participants are still eligible and willing to participate, signed informed consent is obtained. A date to conduct the five-day interventional study (metyrapone and hydrocortisone administration) is then arranged. The 24-hour study is performed after midday (around 2:00–3:00 pm) of day 4 until after midday (around 2:00–3:00 pm) of day 5. HABS: human automated blood sampler