Testosterone and DHT (dihydrotestosterone) aren’t rivals. DHT is a stronger hormone that the body makes from testosterone. They do different jobs, though, because testosterone works across the whole body while DHT works mostly in a few tissues where it is made.1PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects So the hormone behind a receding hairline or a growing prostate is mostly DHT, not testosterone as a whole. That also means drugs can lower DHT while leaving many of testosterone’s other effects in place.
How Testosterone Becomes DHT and Why DHT Is Stronger
An enzyme called 5-alpha reductase turns testosterone into DHT.2PubMed. Role of 5 alpha-reductase in health and disease It comes in two types, type 1 and type 2.3The Journal of Clinical Endocrinology & Metabolism. Marked Suppression of Dihydrotestosterone in Men with Benign Prostatic Hyperplasia by Dutasteride, a Dual 5α-Reductase Inhibitor Type 2 dominates in the prostate, while type 1 works in places like the liver and skin.4PubMed. Steroid 5alpha-reductases and 3alpha-hydroxysteroid dehydrogenases: key enzymes in androgen metabolism Because the conversion happens inside cells, DHT is made mostly in the tissues that use it rather than being sent through the blood the way testosterone is.5PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects The result is that DHT inside the prostate can reach levels up to 10 times higher than testosterone in the blood.6PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects
Blood levels of DHT stay low even when tissue levels are high, which means blood numbers understate its local role. Two people with the same blood testosterone can end up with different amounts of DHT at the follicle or prostate, depending on how much enzyme their tissues carry.
Both hormones work by locking onto the same switch in cells, the androgen receptor. DHT binds that receptor with over three times the affinity of testosterone.7PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects It also stays attached far longer, with a half-life on the receptor of about 40 hours versus 15 hours for testosterone in animal tissue.8PubMed. Binding properties of androgen receptors. Evidence for identical receptors in rat testis, epididymis, and prostate. A given amount of DHT therefore sends a stronger, longer-lasting signal. Tissues switch DHT off by converting it to a much weaker hormone, and the liver uses this route to clear excess androgen.9PubMed. Steroid 5alpha-reductases and 3alpha-hydroxysteroid dehydrogenases: key enzymes in androgen metabolism
Tissues with lots of the converting enzyme get a strong DHT signal, while tissues with little of it mostly see testosterone’s weaker one. That is why shutting down the enzyme noticeably affects the prostate and scalp but leaves muscle and blood production much less changed.
Which Body Parts Depend on DHT and Which on Testosterone
Some of the clearest lessons come from people who can’t make DHT. Some genetic males are born with a faulty type 2 enzyme and can’t make much DHT.10PubMed. Role of 5 alpha-reductase in health and disease They have testes but are born with ambiguous or female-looking external genitals.11PubMed. Role of 5 alpha-reductase in health and disease At puberty they partly masculinize, developing a deeper voice, muscle, sperm, pubic and underarm hair, and usually a male gender identity.12PubMed. Role of 5 alpha-reductase in health and disease Testosterone alone can handle those changes. Sex drive, voice deepening and sperm production run largely on testosterone. DHT is needed for prostate growth, external genitals, male-pattern facial and body hair, and male-pattern baldness.13PubMed. Role of 5 alpha-reductase in health and disease These cases describe people who lacked DHT from before birth, so their outcomes can’t be copied directly onto an adult who lowers DHT with medication, whose genitals and prostate have already developed.
In normal development, DHT also matures the penis and scrotum at puberty and maintains the prostate and seminal vesicles.14Wikipedia. Dihydrotestosterone In boys with delayed puberty, DHT treatment sped growth to normal growth-spurt rates.15PubMed. Androgen-stimulated pubertal growth: the effects of testosterone and dihydrotestosterone on growth hormone and insulin-like growth factor-I in the treatment of short stature and delayed puberty Unlike testosterone, it did this without raising growth hormone, which appears to rise through testosterone’s conversion to estrogen.16PubMed. Androgen-stimulated pubertal growth: the effects of testosterone and dihydrotestosterone on growth hormone and insulin-like growth factor-I in the treatment of short stature and delayed puberty
DHT and the Prostate
DHT helps the prostate develop, but in adults it can drive overgrowth.17PubMed. The role of dihydrotestosterone in benign prostatic hyperplasia It is central to benign prostatic hyperplasia (BPH), the non-cancer enlargement that causes urinary trouble in older men.18PubMed. Dihydrotestosterone and the prostate: the scientific rationale for 5alpha-reductase inhibitors in the treatment of benign prostatic hyperplasia 5-alpha reductase inhibitors such as finasteride and dutasteride lower DHT production.19PubMed. Dihydrotestosterone and the prostate: the scientific rationale for 5alpha-reductase inhibitors in the treatment of benign prostatic hyperplasia They shrink the prostate, improve symptoms and urine flow, and cut the risk of sudden inability to urinate and of surgery.20PubMed. Dihydrotestosterone and the prostate: the scientific rationale for 5alpha-reductase inhibitors in the treatment of benign prostatic hyperplasia Dutasteride blocks both enzyme types, which suppresses DHT more fully.21The Journal of Clinical Endocrinology & Metabolism. Marked Suppression of Dihydrotestosterone in Men with Benign Prostatic Hyperplasia by Dutasteride, a Dual 5α-Reductase Inhibitor
These DHT blockers work gradually, because the gland has to shrink over time. Muscle-relaxing pills, by contrast, loosen the outflow within days. If the drug is stopped, DHT generally recovers and the gland tends to grow again, so the benefit lasts only as long as the treatment does.
PSA is a blood test used to screen for prostate problems, and DHT blockers lower its readings because they shrink prostate tissue. A man on one of these drugs should ask his doctor how his PSA numbers will be interpreted. Without that context, a lowered reading could be misread as reassurance.
Advanced prostate cancer adds a twist. Some prostate cancers keep growing even after testosterone is cut to very low levels.22PubMed Central. Dihydrotestosterone synthesis bypasses testosterone to drive castration-resistant prostate cancer These tumors can make DHT through a route that skips testosterone, starting from other adrenal hormones.23PubMed Central. Dihydrotestosterone synthesis bypasses testosterone to drive castration-resistant prostate cancer Some carry a gene change that speeds up this DHT production.24PubMed Central. A gain of function mutation in DHT synthesis in castration-resistant prostate cancer This explains why treatment may need drugs beyond testosterone suppression, and why DHT remains a target even late in the disease.
DHT, Testosterone and Hair Loss
Male-pattern baldness requires DHT, as people unable to make it don’t develop it.25PubMed. Role of 5 alpha-reductase in health and disease DHT shortens the hair growth phase, so each cycle produces a smaller, finer hair.26PubMed Central. Cause of Androgenic Alopecia: Crux of the Matter Thick hairs gradually turn into fine fuzz and shedding rises.27PubMed Central. Cause of Androgenic Alopecia: Crux of the Matter In mice, DHT caused early hair regression and thinning that a receptor-blocking drug partly reversed.28PubMed. Dihydrotestosterone-induced hair regrowth inhibition by activating androgen receptor in C57BL6 mice simulates androgenetic alopecia One proposed model holds that DHT works indirectly, by helping thicken and scar tissue around follicles, starving them of space and supply.29PubMed. A hypothetical pathogenesis model for androgenic alopecia: clarifying the dihydrotestosterone paradox and rate-limiting recovery factors
Your testosterone level doesn’t predict who goes bald. Men with normal testosterone still lose hair if their scalp follicles are sensitive to DHT, and men with high testosterone don’t necessarily go bald. Follicle sensitivity, which is largely inherited, decides who is affected. Testosterone matters here mainly because it supplies the raw material for DHT.
Because the shrinkage is slow and cycle-by-cycle, results from lowering DHT take months. Follicles that have been miniaturized for a long time may not fully recover, so earlier treatment is likelier to help. Options like finasteride are worth discussing with a doctor.
Muscle, Bone and Blood
Despite its power at the receptor, DHT has weak muscle-building effects in people.30PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects Muscle contains an enzyme that quickly breaks DHT into weak products.31PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects In mouse fast-twitch muscle, DHT did raise protein building where testosterone didn’t.32PubMed Central. Dihydrotestosterone stimulates amino acid uptake and the expression of LAT2 in mouse skeletal muscle fibres through an ERK1/2-dependent mechanism Lab findings like that don’t yet show DHT is a better muscle hormone in humans. DHT also can’t be turned into estrogen, so high doses carry little estrogen-type side effect risk.33PubMed Central. Anabolic-Androgenic Steroid Misuse: Mechanisms, Patterns of Misuse, User Typology, and Adverse Effects
Testosterone protects bone both directly and by being converted to estrogen.34PubMed Central. Testosterone and the Male Skeleton: A Dual Mode of Action In older men on testosterone, bone density gains tracked rises in estrogen most closely.35PubMed Central. Relation of Testosterone, Dihydrotestosterone, and Estradiol With Changes in Outcomes Measures in the Testosterone Trials Estrogen change also best predicted gains in sexual desire.36PubMed Central. Relation of Testosterone, Dihydrotestosterone, and Estradiol With Changes in Outcomes Measures in the Testosterone Trials In mice, testosterone reduced both belly and under-skin fat, while DHT reduced only under-skin fat.37PubMed Central. Testosterone metabolites differentially regulate obesogenesis and fat distribution
Blood is the clearest case of testosterone working without DHT. Testosterone treatment raised red blood cell count about 9% and hemoglobin about 8% over a year.38PubMed Central. Testosterone alters iron metabolism and stimulates red blood cell production independently of dihydrotestosterone Adding finasteride to block DHT didn’t change those rises.39PubMed Central. Testosterone alters iron metabolism and stimulates red blood cell production independently of dihydrotestosterone Blocking DHT therefore won’t stop testosterone from thickening the blood, so men on testosterone therapy still need blood counts checked even if they take a DHT blocker.
DHT and Testosterone in Women
Women make both hormones in small amounts. Women with PCOS tend to have higher testosterone and higher free DHT than other women.40PubMed. Testosterone to dihydrotestosterone ratio as a new biomarker for an adverse metabolic phenotype in the polycystic ovary syndrome Their total DHT often isn’t higher, though.41PubMed. Testosterone to dihydrotestosterone ratio as a new biomarker for an adverse metabolic phenotype in the polycystic ovary syndrome So their ratio of testosterone to DHT runs higher, about 3.6 versus 2.7 in one comparison.42Ginekologia Polska. Total testosterone to dihydrotestosterone ratio assessed by LC-MS/MS predicts a worse metabolic profile not only in PCOS patients A higher ratio goes with more weight, waist size, and insulin resistance.43PubMed. Testosterone to dihydrotestosterone ratio as a new biomarker for an adverse metabolic phenotype in the polycystic ovary syndrome The same link appeared in women without PCOS.44Ginekologia Polska. Total testosterone to dihydrotestosterone ratio assessed by LC-MS/MS predicts a worse metabolic profile not only in PCOS patients
Excess hair growth and acne in PCOS reflect androgen effects on the skin, and the hormone pattern may hint at metabolic risk worth checking. A woman with high androgens can ask about glucose and insulin testing. The testosterone-to-DHT ratio is a research measure, not yet a routine test. Women who are pregnant or could become pregnant shouldn’t use DHT blockers, because DHT shapes a male fetus’s genitals.
Testing Your DHT and Testosterone Levels
Older antibody-based blood tests report DHT higher than the more precise mass-spectrometry method.45PubMed. Simultaneous measurement of serum testosterone and dihydrotestosterone by liquid chromatography-tandem mass spectrometry Other substances in blood get counted as DHT.46PubMed Central. Validation of a testosterone and dihydrotestosterone liquid chromatography tandem mass spectrometry assay: Interference and comparison with established methods The gap is widest and least predictable when DHT is low.47PubMed Central. Validation of a testosterone and dihydrotestosterone liquid chromatography tandem mass spectrometry assay: Interference and comparison with established methods So compare results only from the same lab and method. It’s also fair to ask whether your lab used mass spectrometry, often listed as LC-MS/MS on reports.
Blood DHT doesn’t reflect levels inside the prostate or scalp, so a normal result doesn’t rule out hair loss. Doctors usually treat symptoms rather than chase a DHT number, and testosterone is the main number checked for low-T symptoms. On a DHT blocker, blood DHT falls while testosterone often stays the same or rises slightly, because less of it is being converted.