EP 94: Men Talk: The Decline of Serum Testosterone Levels

The Decline of Serum Testosterone Levels 

In this episode, we will talk about the decline of serum testosterone levels among young Adult Men in the USA. Testosterone is a sex hormone that plays a vital role in the body. It regulates the sex drive, bone mass, and fat distribution.

In addition to that, testosterone is responsible for muscle mass and strength. It is also in charge of sperm production and red blood cells. And small circulating testosterone is converted by the body to estradiol, a form of estrogen.

Mammals have >95% of T fused by Leydig’s cells of the testes and are regulated through the hypothalamic-pituitary-testicular (HPT) axis.

The adrenal glands also produce testosterone but in small amounts. However, the amount produced depends on gender. So, it means different areas have different amounts.

A Decline of Serum Testosterone Levels in Men

A study from 1999 to 2016 showed that the testosterone levels in young adult men and adolescent males with an average body mass index resulted in a decline, as presented in the 2020 American Urological Association Virtual Experience

The reason for this decline in testosterone level is attributed to age. It means that the decrease in these levels is time-dependent. However, the overall reduction in testosterone levels is caused by multiple etiologies. 

Researchers used data from the National Health and Nutrition Examination Surveys (NHANES) dating from 1999 to 2016 to analyze serum testosterone level changes in 40-45 AYA males. 

This study found a few factors affecting the decline of serum testosterone levels. These are as follows:

  • Age
  • Race
  • BMI
  • Comorbidity status
  • Alcohol intake
  • Smoking
  • Physical activity levels

Here are acceptable testosterone levels for men by age group

  • Early Teens: Between 12 to 13 years old, a person should have 7-800 ng/dL. But by 15 to 16 years old, the ng/dL should be 100-1,200.
  • Late Teens: Anyone between 17 to 18 years old have normal testosterone levels between 300 and 1,200 ng/dL.
  • Adults: An adult (19 years and older) should have anywhere between 240 and 950 ng/dL.

Mean Total Testosterone Decrease: 

  • 1999-2000 (605.39 ng/dL)
  • 2003-2004 (567.44 ng/dL)
  • 2011-2012 (424.96 ng/dL)
  • 2013-2014 (431.76 ng/dL)
  • 2015-2016 (451.22 ng/dL)

An increased BMI is associated with decreased total testosterone levels (P < .0001), with the mean BMI increasing from 25.83 in 1999-2000 to 27.96 in 2015-2016 (P = 0.0006). 

It was noted that even men with an average BMI of 18.5-24.9 had declining total testosterone levels of P < .05 during the same time frames.

Limitations of the Study

The study was a cross-sectional study design, a type of observational study. It is self-reported activity leading to potential bias and testosterone levels are only measured once. However, there were no results given on the participant’s symptoms. It is also the most extensive study of its kind.

Potential Causes Of Decline of Serum Testosterone

  • Increased Obesity/BMI
  • Diet/phytoestrogens 
  • Declined physical activity
  • Fat percentage
  • Marijuana use 
  • Environmental toxins

Increased Obesity/BMI

People with moderate obesity have decreased total testosterone. This decrease could be due to insulin resistance that is associated with reductions in sex hormone-binding globulin. Severe obesity connects with reductions in free testosterone levels.
 
Researchers believe it is due to a suppressed hypothalamic-pituitary-testicular axis. Obesity also affects iron metabolism and overactivity. It can further contribute to low circulating total T levels.

Diet

A small study conducted in 2016 investigated the dietary patterns associated with serum total T levels and their predictive effect on hypogonadism (low sex drive) and body composition.

Anthropometry, blood biochemistry, and food frequency questionnaires were collected for 125 adult men [1].

People whose diet is mainly composed of bread, pastries, and dairy products and those who rarely eat homemade food or dark green vegetables are most likely at risk for unhealthy body composition.

When the body composition suffers, it can increase visceral fat and decrease skeletal muscle mass. This result can also lead to lower serum total T levels.

How do endocrine disruptors affect the body?

When absorbed in the body, an endocrine disruptor can decrease or increase normal hormone levels, mimic the body’s natural hormones, or alter the natural production of hormones.

Examples: BPA, PFAS, Phytoestrogens, Phthalates, Triclosan &, etc.

Stress Levels Contributes to Decline of Serum Testosterone Levels

Stress can raise your cortisol, which is a hormone that can lower your testosterone once elevated. Reducing stress also reduces testosterone production. So if you want to reduce stress, you must get enough sleep and live a more balanced lifestyle. Exercising also helps and so does proper nutrition in your diet. 

Doing Physical Activity

A 2016 study of men with obesity found that regular exercise increased T levels than even losing weight. 41 overweight and obese men completed a 12-week lifestyle modification program (aerobic exercise training and calorie restriction).

They measured serum testosterone levels, the number of steps, and the total energy intake [2]. The best exercises to increase T levels are resistance and high-intensity interval training (HIIT). 

One study in men found that interval training helps in boosting T levels. The training consists of 90 seconds of intense treadmill running interspersed with 90 seconds recovery periods.

Results show a significant increase in T levels compared to running on the treadmill for 45 minutes straight [3]. So, to rise the T levels in your body, you must do intense exercises for half an hour or so. Running on the treadmill helps but it might slow down your T-level production. 

Doing cardio has no evidence that it can impact your T-levels, no matter the gender. However, too much cardio may lower your T-levels. 

Can Marijuana Cause a Decline of Serum Testosterone Levels?

A study from 2020 using National Health and Nutrition Examination Survey (NHANES) data from 2011-2016 had some interesting outcomes. They have studied men who are regular marijuana users and how it had impacted their testosterone levels.

This study had identified all men 18 years old and above who answered the substance use questionnaire and underwent laboratory testing for T levels.

In addition to that, regular THC users were defined as those who use THC at least once per month, every month for at least a year. Does this mean marijuana helps increase the T levels? 

Among 5,146 men who met inclusion, 3,027 endorsed using THC at least once in their lives (ever-user). Nearly half of the THC ever-users (49.3%) were regular THC users.

THC use is associated with small increases in testosterone. This means that the rise in T appears to decline as THC use increases. However, T is still higher with any amount of regular use when compared to T in non-users.

Furthermore, this increase was represented by an inverse U-shaped trend with Regular THC users using two-three times per month. It demonstrates the most significant increase in T (+ 66.77 ng/dL) over non-users [4].

Men who smoke it regularly are twice as likely to have sperm with abnormal shape and size. According to one study, males who smoke marijuana at least once a week experienced a reduced sperm count.

Conclusion: 

What you believe you believe is what you become. If you think you’ll lose intelligence by basking in the sun, you probably will. The hippocampus is 90% affected by what you believe and your confidence, in my case, at least.

If you believe that you’re smarter than Einstein, your neurons will fire corresponding signals, and you’ll be seriously reading and studying. It’s all about self-discipline and determination. 

To watch the full episode of Ep. 94, check out our latest by clicking here 👇

TIME STAMPS:

00:00 Intro
00:52 Plugs
02:11 Episode Introduction
04:02 What is testosterone?
06:00 The fun and exciting time of puberty
07:47 The Decline of Serum Testosterone Levels
11:01 The acceptable testosterone levels for men by age group
13:17 Testosterone decreased by 150 points
15:34 Potential cause of testosterone decrease
15:57 1. Obesity
18:39 2. Diet
20:48 3. Environmental Toxins
22:21 4. Stress
23:19 5. Physical Activity
25:26 6. Marijuana use
29:13 Conclusion
31:54 Wrapping up the episode

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