Sex steroid hormones exert important biological effects on the brain. Moreover, an extensive sex steroid metabolism occurs in the brain. In sex steroid metabolism 17hydroxysteroid dehydrogenases (17 -HSDs) play essential roles in catalyzing the final steps in androgen and estrogen biosynthesis. Recently four types of human 17 -HSDs and a pseudogene of the type 1 isoform were identified. To date, 17 -HSD has not been extensively studied in the human brain. Therefore, we investigated the mRNA

more »

... ession of the four isozymes of 17 -HSD as well as the pseudogene of the type 1 isoform in the human temporal lobe to determine the predominant isoforms and, moreover, to elucidate the existence of possible sex and age differences. We studied biopsy materials from the temporal lobe of 34 women, 32 men and 10 children. Quantification of different mRNAs was achieved by competitive reverse transcription-PCR. 17 -HSD 1, 17 -HSD 3 and 17 -HSD 4 were expressed in the human temporal lobe of children and adults, whereas 17 -HSD 2 and the pseudogene of 17 -HSD 1 were not expressed. In adults, 17 -HSD 3 and 17 -HSD 4 mRNA concentrations were significantly higher in the subcortical white matter (17 -HSD 3: 14 591 3457 arbitrary units (aU), mean ...; 17 -HSD 4: 1201 212 aU) than in the cortex (17 -HSD 3: 5428 1057 aU, P<0·0002; 17 -HSD 4: 675 74 aU, P<0·004). 17 -HSD 1 concentrations did not differ significantly between the white matter (3860 1628 aU) and the cortex (2525 398 aU) of adults. In conclusion, the present study demonstrates the expression of 17 -HSD 1, 3 and 4 mRNAs in the human temporal lobe. Together with CYP19 AROM and 5reductase, known to be expressed in the human brain, the expression of 17 -HSD 1, 3 and 4 mRNAs indicates the major importance of local steroid biosynthesis in the brain.