These results indicate that testosterone is optimal, but DHT is below the conventional range. This may reflect deficiency or inhibition of 5-alpha-reductase. Drugs that inhibit 5-alpha-reductase can treat BPH and male pattern baldness.
A low serum DHT may indicate deficiency or inhibition of the 5-alpha-reductase enzyme.
Dihydrotestosterone is the most potent of the androgen hormones. It is primarily synthesized from testosterone via 5-alpha reductase in the prostate, liver, and skin, and most circulating DHT is bound to SHBG. Androgen-sensitive tissues can regulate intracellular DHT by reducing synthesis or increasing metabolism to other compounds so circulating levels don’t necessarily correlate with tissue levels (Swerdloff 2017).
DHT promotes masculine characteristics and development. It plays a significant role in male physiology, including sexual organ development, prostate growth, sebaceous gland activity, hair growth (body, face, and pubic hair), and even male pattern baldness (Kinter 2021).
Levels may decrease with the inhibition of 5-alpha reductase. In men with prostatic hypertrophy, inhibition of 5-alpha reductase will decrease the size and function of the prostate (Swerdloff 2017). Drugs that inhibit 5-alpha-reductase may treat enlarged prostate (BPH) and male pattern baldness.
Low levels of DHT have been associated with insulin resistance, metabolic syndrome, diabetes, dementia (Swerdloff 2017), and ischemic stroke (Yeap 2014). An observational study of 1032 men 66-97 years old found that those with a DHT between 50 and 75 ng/dL (1.74-2.6 nmol/L) had the lowest risk of ischemic stroke while those with a DHT below 50 ng/dL or above 75 ng/dL had the greatest risk (Shores 2014).
References
Shores, Molly M et al. “Testosterone and dihydrotestosterone and incident ischaemic stroke in men in the Cardiovascular Health Study.” Clinical endocrinology vol. 81,5 (2014): 746-53. doi:10.1111/cen.12452
Swerdloff, Ronald S et al. “Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels.” Endocrine reviews vol. 38,3 (2017): 220-254. doi:10.1210/er.2016-1067
Yeap, Bu B. “Testosterone and its metabolites: differential associations with cardiovascular and cerebrovascular events in men.” Asian journal of andrology vol. 20,2 (2018): 109-114. doi:10.4103/aja.aja_50_17