Correction to: Nature Reviews Endocrinology https://doi.org/10.1038/s41574-021-00482-5, published online 19 April 2021.

In the original version of this article, in Fig. 1c, the icons for oxygenated haemoglobin and deoxygenated haemoglobin were incorrectly shown outside of the artery and vein. This error has now been corrected in the HTML and PDF versions of the article.