5a-dihydrotestosteron

The brain, like the seminal vesicles, is able to reduce testosterone to 5a-dihydrotestosterone (DHT) and, like the placenta, the brain aromatizes testosterone to estradiol (Fig. 52-4). Neither conversion occurs equally in all brain regions. The aromatization reaction is discussed below. Regional distribution of 5a-reductase activity toward testosterone in rat brain reveals that the highest activity is found in the midbrain and brainstem, intermediate activity is found in the hypothalamus and thalamus, and the lowest activity is found in the cerebral cortex [1]. The pituitary has higher 5a-reductase activity than any region of the brain, and its activity is subject to changes as... 

Gibb, W., Jeffery, J. 5a-dihydrotestosterone sulfate and cortisone reductase. Biochim. Biophys. Acta 280, 646—651 (1972). 

To convert testosterone into the more active androgen, dihydrotestosterone (5a-dihydrotestosterone), in a reaction catalysed by the enzyme 5a-reductase. 

Steroid hormones These are the oestrogens (mainly oestradiol in women) progesterone, testosterone and 5a-dihydrotestosterone. 

Bromo [ F]fluoride (Section 3.9.1) addition across a double bond was used in the synthesis of fluorine-18-labelled steroids of high specific radioactivity. After addition, the bromine is removed by reduction or by dehydrobromination. [ F]Fluoro-5a-dihydrotestosterone was obtained in about 3% radiochemical yield (Scheme 17) [64] and 6a-p F]fluoroprogesterone in only 0.3% [65]. The yields were quite low but sufficient to allow for animal studies. These reactions had been tested out successfully with simpler model alkenes [66]. 

Within many target tissues testosterone is converted by an NADPH-dependent 5a-reductase into 5a-dihydrotestosterone. That this transformation is important is ch2oh shown by the fact that absence of... 

Abbreviations ABP, androgen-binding protein 5q-DHT. 5a-dihydrotestosterone 5/3-DHT, 5/3-dihy-drotestosterone EGF, epidermal growth factor FSH. folitropin KAP, kidney androgen-induced protein LH, lutropin NGF, nerve growth factor SGF, testis-specific growth factor. 

Within the prostate gland, the steroid hormone testosterone is irreversibly converted to 5a-dihydrotestosterone (DHT), the active androgen in the prostate. Binding of DHT to the AR triggers conformational changes which unmasks the... 

---