As with most things biology, there is a relatively tight range for optimal: insufficiency of compound X is a problem and excess of compound X is a problem as well, for a different, but related, set of mechanisms…. I have been particularly interested in this concept for the duration of my career, seeing this U curve relationship play out time and again in clinical laboratory data. Thus, when I popped open my Today’s Practitioner and read in the recent Lancet Diabetes & Endocrinology edition on cortisol and COVID, the U curve and mortality findings made good sense.
Called the koala stress syndrome, hypoadrenalism is a predictor of poor outcome in ICU patients. Additionally, what the NIHR researchers also found, looking at 3 London hospitals, is that very elevated cortisol (>744 nmol/L) is also a predictor of poor outcome. Those with this high level of cortisol had a median survival of 15 days, compared with those whose cortisol was less than or equal to 744 nmol/L and who had a median survival of 36 days. This cortisol measure was taken within 48 hours of hospital admission for suspected or diagnosed COVID-19.
“Kaplan-Meier plot of survival probability over time. The plot is categorised by baseline cortisol concentration above or equal to and below the cutoff of 744 nmol/L. Shading indicates 95% CI for each curve.” Lancet Diabetes Endocrinol. 2020 Aug;8(8):659-660. doi: 10.1016/S2213-8587(20)30216-3.