Dr. Kyle Gillett (IG: @kylegillettmd) is a dual board-certified physician in family medicine and obesity medicine and an expert in optimizing hormone levels to improve overall health. He is also the host of The Gillett Health Podcast. His work can be found at GillettHealth.com.
In this conversation, Dr. Kyle Gillett and Brett McKay discuss how to optimize your testosterone, symptoms of low T, causes of low T, supplements, TRT, why testosterone levels are dropping, and more
Check out these Podcast Notes on Kyle’s first conversation with Andrew Huberman   
Host: Brett McKay (@artofmanliness)  
While testosterone is the most well-known androgen, there are others such as DHEA and DHT
  • DHT is vitally important for secondary sexual characteristic development 
Estrogen is important for optimal male health 
Testosterone aromatizes and directly converts to estrogen
It is best for males to have high levels of estrogen as long as they feel good, according to Dr. Kyle Gillett
  • Optimal levels of estrogen reduce the risk of heart attacks 
Sex Hormone-Binding Globulin (SHGP): an androgen-binding globulin that is made in the liver and the testes
  • SHGP regulates all the hormones and keeps them stable 
  • The higher the SHGP, the more stable the level will be 
  • Men produce a lot of testosterone when they sleep, so SHGP levels are much higher in the morning 
The most common cause for deficient levels of SHGP is insulin resistance, which is often caused by consuming too many calories, carbohydrates, or sugar 
Total testosterone and free testosterone are the two ways to measure a person’s testosterone 
Total testosterone is the total amount of T whether it is bound or unbound 
Bound testosterone can be attached to albumin or SHGP 
Free testosterone is unbound testosterone  
The free testosterone can be very different in the bloodstream (where it is measured) compared to its levels inside the cell
Muscle building and athletic performance are typically more correlated with free testosterone
How you feel is typically more correlated with total testosterone 
Insurance companies and academic studies typically put more weight into total testosterone, partly because free T is often measured inaccurately 
Low testosterone is often best treated if 1) you have symptoms and 2) have a testosterone level below 400
One blood test alone is not sufficient to diagnose low T
Testosterone levels can vary depending on the quality of your recent sleep and diet 
Dr. Kyle Gillett recommends getting at least two readings
Symptoms of low T vary across systems. Some include:
  • Depression
  • Anxiety 
  • Low libido 
  • Erectile dysfunction 
  • Low sperm production 
Low muscle mass is not a symptom that Dr. Gillett looks for
People who are significantly hypogonadal for a long time are at a much higher risk for osteoporosis, neurodegenerative disease, cardiovascular disease, and others
Metabolic syndrome is the most common cause of low testosterone
Metabolic syndrome can be caused by excess calories, excess carbohydrates, excess sugar, insulin resistance
High fasting insulin results in the liver not producing SHGP 
An individual with metabolic syndrome may be producing enough testosterone, but it could be getting metabolized so fast that it is difficult to use 
Obstructive sleep apnea is the second most common cause of low T 
Theoretically, xenoestrogens could be a cause of low T 
Xenoestrogens are things like phthalates, BPAs, and PCBs
Xenoestrogens bind to various estrogen receptors and can shut down the hormones that lead to testosterone production
Heat damage can contribute to low T 
It is optimal to keep the testes at 91 or 92 degrees
Metabolic syndrome, being overweight, and obstructive sleep apnea are probably the primary causes of falling testosterone levels, according to Dr. Kyle Gillett 
Falling rates may also be caused by “epigenetic drift” or “unnatural selection” where individuals with higher T levels are no longer being selected for as early, and also a lot of individuals are having kids later on in life
  • Parents having children in their 30s and 40s have different maternal and paternal hormone profiles compared to earlier in life 
  • This may be resulting in different hormonal profiles being passed down to offspring
Theoretically, higher T men would have been more willing to go to the front lines in WWI, WWII, and other wars, which increased the chances of them dying and not passing down their high T hormone profile to offspring
Theoretically, higher T men tend to take more risk, and doing so may take them out of the gene pool 
Theoretically, lower T men may be doing better in this high-tech world we live in, causing women to choose them as mates and therefore passing lower T profiles down to subsequent generations 
For most men, an optimal testosterone number is between 500 and as high as you can go naturally
Remember to interpret the T measurement in the context of symptoms or lack thereof 
There is little to no benefit to getting your testosterone above 600, according to Dr. Kyle Gillett   
If a pituitary issue does not cause the low T, then Dr. Gilet starts the patient with lifestyle changes: better sleep, diet, less drinking, getting to a healthy weight, reducing stress, etc.
  • Improvements in these areas help the patient become more insulin sensitive
  • It may take 1-2 months for testosterone to recover through lifestyle changes  
He may also implement medication, such as HCG or a short course of selective estrogen modifiers
Supplements that help optimize testosterone:
  • Creatine (5-10g per day) 
  • L-Carnitine (for athletic performance and body composition)
  • Calcium D-Glucarate (if the patient has high estradiol)
  • Tongkat Ali (signals to the testes to ramp up production) 
TRT is an option when the benefits of increasing T outweigh the risks of remaining at low levels of T, and when the patient understands the risks and the benefits of the therapy 
Risks of TRT:
  • Causes more fluid retention and swelling 
  • Increased blood clot risk if going into a bulk and consuming alcohol
  • “Bad cholesterol” numbers may get worse (watch apo-B)
TRT in and of itself will not improve health; it is a tool to help you achieve your goals 
TRT may reduce your likelihood of getting diabetes 
Most individuals are on TRT indefinitely once they start, but not everyone 
He estimates that 90% of people who start TRT will remain on it indefinitely 
Most will be able to achieve their previous level of T if they were to come off 
Do not do a “huge dirty bulk” in early adolescents
  • He does not advise younger men or boys to intentionally put on weight for football, for example 
  • Putting on too much adipose tissue too young may limit overall growth
Consume enough fiber 
Establish a reasonable balance between cardiovascular exercise and resistance training 
Low quality and insufficient amount of sleep are one of the primary causes of suboptimal hormone profiles in the youth 
For some, creatine supplementation may make sense
Reduce exposure to BPAs and phthalates
Test your water if you live in an area where the risk of contamination is higher
  • Dr. Gilet uses mytapscore.com to test his tap water
Eat whole foods and avoid ultra-processed foods