Dihydrotestosterone

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

BackgroundPotential cardiovascular (CV) risks of testosterone replacement therapy (TRT) are currently a topic of intense interest. However, no studies have addressed CV risk as a function of the route of administration of TRT.MethodsTwo meta-analyses were conducted, one of CV adverse events (AEs) in 35 randomized controlled trials (RCTs) of TRT lasting 12 weeks or more, and one of 32 studies reporting the effect of TRT on serum testosterone and dihydrotestosterone (DHT).ResultsCV risks of TRT: Of 2,313 studies identified, 35 were eligible and included 3,703 mostly older men who experienced 218 CV-related AEs. No significant risk for CV AEs was present when all TRT administration routes were grouped (relative risk (RR) = 1.28, 95% confidence interval (CI): 0.76 to 2.13, P = 0.34). When analyzed separately, oral TRT produced significant CV risk (RR = 2.20, 95% CI: 1.45 to 3.55, P = 0.015), while neither intramuscular (RR = 0.66, 95% CI: 0.28 to 1.56, P = 0.32) nor transdermal (gel or patch) TRT (RR = 1.27, 95% CI: 0.62 to 2.62, P = 0.48) significantly altered CV risk. Serum testosterone/DHT following TRT: Of 419 studies identified, 32 were eligible which included 1,152 men receiving TRT. No significant difference in the elevation of serum testosterone was present between intramuscular or transdermal TRT. However, transdermal TRT elevated serum DHT (5.46-fold, 95% CI: 4.51 to 6.60) to a greater magnitude than intramuscular TRT (2.20-fold, 95% CI: 1.74 to 2.77).ConclusionsOral TRT produces significant CV risk. While no significant effects on CV risk were observed with either injected or transdermal TRT, the point estimates suggest that further research is needed to establish whether administration by these routes is protective or detrimental, respectively. Differences in the degree to which serum DHT is elevated may underlie the varying CV risk by TRT administration route, as elevated serum dihydrotestosterone has been shown to be associated with CV risk in observational studies.

BackgroundAndrogenetic alopecia (AGA) is a genetic disorder caused by dihydrotestosterone (DHT), accompanied by the senescence of androgen-sensitive dermal papilla cells (DPCs) located in the base of hair follicles. DHT causes DPC senescence in AGA through mitochondrial dysfunction. However, the mechanism of this pathogenesis remains unknown. In this study, we investigated the protective role of cyanidins on DHT-induced mitochondrial dysfunction and DPC senescence and the regulatory mechanism involved.MethodsDPCs were used to investigate the effect of DHT on mitochondrial dysfunction with MitoSOX and Rhod-2 staining. Senescence-associated β-galactosidase activity assay was performed to examine the involvement of membrane AR-mediated signaling in DHT-induced DPC senescence. AGA mice model was used to study the cyanidins on DHT-induced hair growth deceleration.ResultsCyanidin 3-O-arabinoside (C3A) effectively decreased DHT-induced mtROS accumulation in DPCs, and C3A reversed the DHT-induced DPC senescence. Excessive mitochondrial calcium accumulation was blocked by C3A. C3A inhibited p38-mediated voltage-dependent anion channel 1 (VDAC1) expression that contributes to mitochondria-associated ER membrane (MAM) formation and transfer of calcium via VDAC1-IP3R1 interactions. DHT-induced MAM formation resulted in increase of DPC senescence. In AGA mice models, C3A restored DHT-induced hair growth deceleration, which activated hair follicle stem cell proliferation.ConclusionsC3A is a promising natural compound for AGA treatments against DHT-induced DPC senescence through reduction of MAM formation and mitochondrial dysfunction.

BackgroundDihydrotestosterone (DHT), the most potent ligand to the androgen receptor, is synthesised from testosterone (T) by 5α-reductase type 1 and 2. While type 1 is expressed in several non-reproductive tissues in both sexes, men also express high levels of the high-affinity type 2 isoform in reproductive tissues; yet women have a higher circulating DHT to T (DHT/T) ratio than men. We hypothesised that the high DHT/T ratio in women is caused by high gut microbiota (GM) 5α-reductase activity or altered β-glucuronidase-induced androgen reabsorption from the gut.MethodsWe used a large cross-sectional subsample of the Swedish CArdioPulmonary bioImage Study (2897 women and 4338 men, 50-65 years of age) with GM composition and functionality determined by metagenome sequencing and circulating androgens determined by liquid chromatography-tandem mass spectrometry.FindingsWe confirmed that women had higher (+194%) circulating DHT/T ratio than men. The relative abundance of microbial genes for 5α-reductase type 1 (P = 3 × 10-4), but not β-glucuronidase, was positively associated with the DHT/T ratio in women. In women, the GM relative abundances of Odoribacter splanchnicus and Parabacteroides distasonis were positively associated with the relative abundance of microbial genes for 5α-reductase type 1 (P -149) and the circulating DHT/T ratio (O. splanchnicus P = 3 × 10-6; P. distasonis P = 5 × 10-5). In mechanistic studies, we observed very high DHT/T ratio in intestinal content of female conventionally-raised but not germ-free mice. In female mice, the DHT/T ratio was 86.9% higher in serum from the portal vein than in inferior vena cava (P = 0.007).InterpretationThese findings demonstrate that the circulating DHT/T ratio is increased by GM 5α-reductase activity in females. We propose that the GM acts as an endocrine organ influencing the androgenic status in females.FundingSee Acknowledgements.