5α-Dihydroprogesterone (5α-DHP, allopregnanedione,[1] or 5α-pregnane-3,20-dione) is an endogenous progestogen and neurosteroid that is synthesized from progesterone.

5α-DHP is metabolized by the aldo-keto reductases (AKRs) AKR1C1, AKR1C2, and AKR1C4 with high catalytic efficiency.

[2][3][6][7] It has also been found to act as a negative allosteric modulator of the GABAA-rho receptor.

[10] In addition, it is a weak agonist of the pregnane X receptor (PXR) (EC50 >10,000 μM), with approximately six-fold lower potency relative to its 5β-isomer, 5β-dihydroprogesterone.

[12][13] A study found that 41% of allopregnanolone that was administered via injection was transformed into 5α-DHP in the rat brain.