DHT is created from testosterone via 5-alpha reductase (5αR). DHT is our most potent androgen and is responsible for many of the benefits of testosterone.
You also get 5-beta reductase (5βR), which creates 5β-DHT and other β reduced steroids. We don’t want to be betas, we want to be alphas.
5α-DHT has the strongest androgenic effects, whereas 5β-DHT has very weak or even antagonistic androgenic effects (R). The bigger your 5β steroid pool, the more it will compete with and displace 5α reduced steroids.
What’s important is the 5α to 5β ratio. We still need 5βR, since it’s involved in inactivating various steroid hormones, creating neurosteroids, bile synthesis, red blood cell production, detoxification, etc (R).
The smaller the ratio, the less androgenic we can feel. The higher the ratio, meaning more 5α to 5β reduced steroids, the more androgenic we’ll feel.
Thyroid function and 5α and 5β reduced steroids
A low 5α to 5β ratio can leave us feeling like we have low testosterone, due to having low DHT. Hypothyroid individuals tend to have lower levels of testosterone, but much lower levels of DHT compared to testosterone (R). For example, a hypothyroid individual will have a 1:1 ratio of testosterone to DHT, whereas a hyperthyroid individual will have a 6:1 ratio.
“Indeed, the plasma level of dihydrotestosterone in hyperthyroid men is elevated more than sixfold” (R).
T3 boosts 5αR
As you can see from the graph below, hypothyroid rats, treated with T4, have much higher 5αR compared to hypothyroid rats without T4. Combining growth hormone (GH) and T4 had the best effect (R).
T4 is a precursor thyroid hormone to T3, which is the active thyroid hormone.
T3 specifically stimulates 5αR (R).
Hypothyroidism and DHT deficiency
Some studies have shown and suggested that (severe) hypothyroidism can lead to DHT-deficient symptoms.
“When congenitally absent (namely 5αR), it causes the syndrome described by Imperato-McGinley in the Dominican Republic, the so-called “12-year old penis,” in which 46XY individuals with ambiguous external genitalia virilize at puberty… Patients with marked hypothyroidism also have a substantial decrease in hepatic 5a-reductase activity. Although the authors state that this is reversed by the administration of thyroid hormone, they do not tell us which thyroid hormone.” (R)
Basically, low T3 can lead to micropenis due to very low DHT. This is obviously more important during puberty when penile growth is stimulated by DHT. But DHT is likely also very important for flaccid hang. Low DHT can lead to a short flaccid hang, whereas high DHT can make someone look hung like a horse. Grower vs show-er is what I’m trying to say.
Anorexic individuals also have very low DHT, due to low T3. “The fascinating observation in anorectics is that treatment with T3 completely reverses the abnormalities; the androsterone:etiocholanolone ratio (5α to 5β reduced steroids respectively) triples and cortisol metabolism returns to normal.” (R)
On the top side of the funnel/pathway, TRH (released from the hypothalamus to stimulate the release of TSH) inhibits 5αR and increases prolactin (R). In general, DHT and prolactin will have an inverse relationship. Make sure you optimize thyroid function for low prolactin and high DHT.
Tests to do
- Total and free T4 and T3
- Total and free T
- (Optional) DUTCH test that will look at the ratio of your 5α and 5β reduced steroids
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