Dutasteride (Avodart) has more complete suppression of all three 5α-reductase isoenzymes. It inhibits types 1 and 2 better than finasteride, leading to it causing further reduction in DHT at 6 months than the older drug (% versus %).  It also reduces intraprostatic DHT 97% in men with prostate cancer at 5 milligrams per day over three months.  A second study with mg/d for 4 months decreased intraprostatic DHT even further by 99%.  It has also been shown to inhibit the 5α-R3 isoenzyme in vitro ,  suggesting that dutasteride may be a triple 5α reductase inhibitor in vivo . 
Manganese is known to impede the male reproductive function, however, the mechanisms through which the adverse effects are mediated are not clearly elucidated. In order to get insight into those mechanisms, the effects of manganese on the biosynthesis of testosterone by primary rat Leydig cells were examined. Primary Leydig cells were exposed to various concentrations of manganese chloride for different periods of time. Dose and time-dependent reductions of human chorionic gonadotropin (hCG)-stimulated testosterone level were observed in the culture medium. The expression of Steroidogenic Acute Regulatory (StAR) protein and the activities of P450 side-chain cleavage (P450scc) and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) enzymes were also detected. The expression of StAR protein stimulated by hCG was suppressed by manganese chloride at all concentrations (, , mM) and time points (2, 4, 24, 48 h) tested. Progesterone productions treated with 22R-hydroxycholesterol or pregnenolone were reduced after treated by manganese chloride for 24 or 48 h, respectively. The manganese exposure effect on cell viability was significant at and mM at 24 h, while at 48 h it was significant at every concentration tested. The decreasing effect of manganese on mitochondrial membrane potential was significant at every concentration measured and every time point tested. These data suggest that manganese exposure for 2 and 4 h inhibited rat primary Leydig cell steroidogenesis by decreasing StAR protein expression while 24 and 48 h exposure of manganese chloride caused adverse effects on both StAR protein and P450scc and 3beta-HSD enzyme activity to reduce steroidogenesis. Manganese may also disrupt StAR expression and/or function secondary to mitochondrial dysfunction.