11-Beta Hydroxysteroid Dehydrogenase (HSD11B) is the name of a family of enzymes that catalyzes the conversion of inert 11 keto-products (cortisone) to active cortisol, or vice versa, thus regulating the access of glucocorticoids to the steroid receptors.

In humans, there are two HSD11B isoforms:

1. HSD11B1 is NADPH-dependent. Highly expressed in key metabolic tissues including liver, adipose tissue, and the central nervous system. In these tissues, HSD11B1 reduces cortisone to the active hormone cortisol that activates glucocorticoid receptors.
2. HSD11B2 is NAD⁺-dependent. Expressed in aldosterone-selective tissues. In these tissues, HSD11B2 oxidizes cortisol to cortisone and prevents illicit activation of the mineralocorticoid receptor.

References

• JR Seckl. 11B-Hydroxsteroid Dehydrogenase in the Brain: A Novel Regulator of Glucocorticoid Action? Frontiers in Neuroendocrinology 18, 49-99 (1997)