Someone recently told me that their doctor told him that he shouldn’t use scrotal TRT, since it will cause toxic DHT. Whot!?
Can DHT even be toxic?
Clarification
Scrotal TRT is when someone applies a testosterone cream or gel on his scrotum as a form of TRT to normalize his testosterone levels.
A few good reason for topical TRT include:
- It mimics the natural daily rhythm.
- You don’t have to inject yourself.
- It converts significantly less to estrogen – thus estrogen control is better.
- It doesn’t cause as long term suppression compared to T injections with a long ester. LH will be back to normal in roughly 24 hours after T application.
The reason for scrotal application is because the absorption is 8-10 times better there compared to any other area of the body.
However, scrotal skin also contains the highest amount of 5-alpha reductase compared to anywhere else on the body, which some people think can be a problem.
Thus, applying testosterone on the scrotum will result in significantly higher DHT compared to applying it on the shoulders for example. Topical application of testosterone will almost always result in more DHT compared to injectable testosterone.
Safety of very high DHT levels
The main concerns with DHT are prostate cancer (or growth at least), hair loss and cardiovascular disease.
Many studies have been done looking at DHT as an alternative to testosterone as a hormone replacement therapy, due to it being non-aromatizable. The main reasons for using DHT instead of T (according to the researchers) are because DHT doesn’t promote prostate growth or contribute to CVD similar to what testosterone can do, which is due to excess estrogen (R, R).
Additionall, DHT does not negatively affect liver function or the lipid profile or cause any major side effects for that matter, such as hair loss (R).
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The reference range for DHT is 14 to 77 ng/dL (0.47 to 2.65 nmol/L) with some reference ranges going up to 5 or 6nmol/L (144-173ng/dl) depending on what the study deems as normal.
The average T to DHT ratio is 9-12:1 (R). Let’s use 10:1 for simplicity.
If you maximize your testosterone to 1000ng/dl, DHT will likely be around 100ng/dl or 3.5nmol/L.
We want DHT since it’s our most powerful androgen and a lot of testosterone’s benefits are due to DHT. This study found that low DHT can be associated with symptoms of hypogonadism even in men with normal testosterone (R).
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How high can you go with exogenous DHT
All DHT hormone replacement studies have been done with topical/transdermal DHT.
- 125-250mg DHT topically daily increased DHT to about 8.5 ± 6.5nmol/L (R).
- 16, 32, and 64mg DHT increase DHT levels to 8-11, 12-17, and 14-24 nmol/L, respectively (R). Serum T levels decreased to 75, 56, and 36% of baseline after 14 days of 16, 32, and 64 mg/day DHT gel. So not even complete suppression at 64mg.
- 70mg topical DHT increased serum DHT to 25.8 nmol/L (R).
How high does DHT go with topical testosterone
Topical testosterone can be applied on the scrotum or anywhere else on the body. Absorption on the scrotum is 8-10 times better, but it has significantly more 5-alpha reductase, which some docs think is a problem.
You also get 2 main ways of applying testosterone, namely patch or gel.
Non-scrotal studies
Study 1 (R):
- After T patch application mean serum DHT levels rose to about 1.3-fold above the baseline
- After T gel application (50 and 100mg doses):
- serum T increased to 17–20 nmol/L and 22–30 nmol/L, respectively
- serum DHT increased to 4 nmol/L and 7 nmol/L, respectively, throughout the 180 days.
Study 2 (R):
Topical T increased T to roughly 800ng/dl and DHT to 1.7nmol/L (50ng/dl) and E2 to 25pg/ml.
Combination study
This 2005 study found that (R):
- 125mg non-scrotal T increased T from 8 to 20 nmol/L and DHT to around 2-3 nmol/L.
- 25mg scrotal T also increased T from 8 to 20 nmol/L while boosting DHT to around 4-5 nmol/L
Scrotal T
Study 1 (R):
Topical T patch increased:
- T from 1.5 +/- 0.4 nmol/L to
- 15.2 +/- 3.4 nmol/L at week 4 (10mg T patch)
- 18.6 +/- 3.3 nmol/L at week 8 (15mg T patch)
- 17.3 +/- 2.8 nmol/L at week 12 (15mg T patch)
- DHT to 6.15nmol/L with 10mg and to 8.2nmol/L with the 15mg T patch. (T for DHT ratio was 2.47:1. The normal testosterone/DHT ratio is 9:1 to 12:1). (R)
Study 2:
50mg scrotal T increase T to 670ng/dl and DHT to 3.47-4.85nmol/L (100 and 140ng/dl). The increase in DHT in this study was not dose-dependent (they used 3 doses: 12.5, 25, 50 mg) (R). DHT would likely have increased more after a few weeks of consistent use.
Study 3:
15mg T scrotal patch increased T to 531ng/dl and DHT to 7.9nmol/L (228ng/dl) after 4 week and went up to 10.8nmol/L (315ng/dl) for the remainer of the study duration (9 to 12 months). Compared to normal men with similar T, the scrotal T group had almost 4 times higher DHT; 10.8 vs 2.9nmol/L (R).
Study 4
16mg scrotal T patch increased testosterone to around 700ng/dl and DHT to 6.9nmol/L (200ng/dl) after 12 months of use, which 4 times higher than T enanthate injection (R).
Application summary
The highest DHT with topical DHT application was almost 26nmol/L at 70mg daily.
With topical T (non-scrotal), DHT went up to 7nmol/L with 100mg dose.
With scrotal T, DHT went to 10.8 with 15mg scrotal patch over 9 months, which was much higher compared to the gels.
Summary
Topical DHT has been used for up to 2 years, which can increase DHT levels on average to 26nmol/L, and hasn’t been shown to cause side effects (R).
Why would scrotal T cream or gel, which on average increases DHT to 4.86nmol/L, cause toxic DHT?
Yes, scrotal T (as a patch) can increase DHT about 4 times as much compared to injectible T, but it’s still about 3 times lower than what they achieve with topical DHT hormone replacement.
Given that very high levels of serum DHT, achieved with topical DHT, doesn’t cause sides, why would scrotal T?
Myth busted guys. Scrotal T won’t cause toxic levels of DHT.
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