Weight Lifting, Weight Training, Bench Press & Bodybuilding
October 4, 2023

Natural Ways To Increase Testosterone Bioavailability
In Athletes - Part I

By Ivan Nikolov

Increase testosterone naturally

Being a natural athlete I’ve always sought to find more ways to increase testosterone levels naturally. The question I’ve always asked myself was what are the variables, which determine how much testosterone is boiavailable.

I’ve read articles before, giving some advice on what in my every day life causes my test levels to go up and what causes them to go down.

But after an extensive research I couldn’t find an article, explaining in detail how and actually what exactly I should manipulate directly in my system to achieve the effects I desired – namely not only higher levels of circulating testosterone but also how much of it will be available to the corresponding receptors in the cell walls.

Moreover, I wanted to know all this in regards to natural bodybuilding…

So, I decided to do some good digging and reading and then if I manage to put things together, to lay that in writing form so that others can benefit as well.

Without wasting even a minute more I will start this off by describing what testosterone is and what it does in the human body. Testosterone is a steroid hormone with anabolic and androgenic properties. It is the main hormone, responsible for the increase in lean muscle tissue, increased libido, energy, bone formation, and immune function.

Testosterone is secreted in the testes in men and in the ovaries in women. Small amounts are also secreted in the adrenal glands. Testosterone is derived from cholesterol. The levels of testosterone in men range between 350 and 1,000 nanograms per deciliter (ng/dl). After the age of 40 these normal levels start dropping by roughly 1 per cent a year.

In the blood stream testosterone circulates in great percentage bound to so called binding proteins. Sex Hormone Binding Globulin or SHBG is the one that concerns us the greatest.


Because this is the main reason why testosterone might not be available to reach the cell receptor. When testosterone gets attached to SHBG, it is no longer able to perform its anabolic functions.

What elevates SHBG: Anorexia nervosa, Hyperthyroidism, Hypogonadism (males), Androgen insensitivity/deficiency, Alcoholic hepatic cirrhosis (males), Primary biliary cirrhosis (females).

What suppresses SHBG: Obesity, Hypothyroidism, Hirsutism (females), Acne vulgaris, Polycystic ovarian disease, Acromegaly, Androgen-secreting ovarian tumors

Less than 1% of the circulating testosterone is in a free form in males (less that 3% in females). Only when in a free form this hormone can exhibit its properties by connecting to the androgen receptors on the cell walls. Based on a study 14 to 50 per cent of the testosterone is bound to SHBG in males and 37 to 75 in females.

It is worth mentioning that SHBG poses very high affinity for binding to testosterone. Therefore, changes in the SHBG levels noticeably influence the level of bioavailable testosterone.

Let’s discuss for a moment what exactly a testosterone bioavailability is. Other than SHBG there are two more testosterone-binding proteins, also called carriers. One of them is albumin. It is a low-affinity binding protein, thus testosterone bound to it is considered “bioavailable”.

Albumin binds to testosterone in the range 45 to 85 per cent in men (25 – 65 in women). The third carrier is the cortisol binding globulin, which binds also with low-affinity to less that 1 % of the testosterone in circulation.

The free androgen index (FAI) indicates the amount of bioavailable testosterone. FAI is the sum of the free testosterone and the albumin and cortisol binding globulin. Or it’s the total serum testosterone minus the SHBG-bound testosterone.

It is now clear why we should focus our attention on the properties of SHBG. The levels of this binding protein increase when there is excess estrogen present.

testosterone bioavailabilty - increase naturally

Conversely, SHBG levels drop if the testosterone levels are elevated. Here I should mention the fact that SHBG exhibits higher affinity to testosterone than to estrogen. Now, pay close attention…

It’s a well-known fact that testosterone is an estrogen precursor – it will convert to estrogen under the influence of the enzyme aromatase. Nothing that we don’t know so far.

Here is where it gets interesting.

Suppose that we have normal testosterone levels and we don’t suffer from any of the health ailments, which influence the SHBG levels. That means that SHBG levels are normal, too.

Bare with me now. If more of this testosterone is converted to estrogen due to abnormal aromatase levels, the SHBG I will increase as well. SHBG, being more readily bound to testosterone, will leave us with excess estrogen levels in the system, which in turn will stimulate increased production of the SHBG protein from the liver.

This whole process ultimately amplifies estrogen levels. Estrogen readily binds to the androgen receptors in cells thus leaving less opportunity for the free testosterone. Even more important, estrogen is the messenger molecule that signals the brain to decrease testosterone production.

Another thing of great importance is the fact that over 40 per cent of the SHBG protein circulates unbound in the blood stream in men (over 80 per cent in women), and albumin circulates unbound almost all of the time.

Thus increase in the total testosterone levels does not produce any noticeable changes in the free testosterone levels unless there is a significant increase like the one seen after synthetic steroid hormone administration.

Well, this whole story brings us to the conclusion that the main approach should be - to keep the testosterone bioavailability high.

In this regard a natural athlete should strive to:

** Attempt to increase the total testosterone as a means of keeping the testosterone levels from plunging

** Prevent testosterone levels from getting low

** Block the testosterone-binding effects of SHBG

** Lower the levels of the enzyme aromatase - less testosterone conversion to estrogen.

To learn more about Fitness & Nutrition be sure to stop by Web site. Until Next time! Or read Part II here.

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