<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A substance that blocks an enzyme needed by the body to make dihydrotestosterone (a male sex hormone made from testosterone). Dihydrotestosterone can cause the prostate to grow. 5-alpha reductase inhibitors are used to shrink an enlarged prostate gland and to improve the flow of urine in a condition called benign prostatic hyperplasia (BPH). A 5-alpha reductase inhibitor is a type of enzyme inhibitor.</n0:def-definition><n0:def-source>NCI-GLOSS</n0:def-source></n0:ComplexDefinition>
<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>Any substance that inhibits steroid 5-alpha-reductase, an enzyme that converts testosterone into dihydrotestosterone (DHT). Since DHT has three times greater affinity for androgen receptors than testosterone, inhibition of 5-alpha-reductase results in a strong reduction in the androgenic effects of testosterone.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>