How do T3/T4 work_VW Physique

Posted 1 year ago

What is T3/T4 and how do they work?

Many of you within the bodybuilding realm will know that assisted bodybuilders use the hormones T3 (triiodothyronine) and T4 (thyroxine) when dieting for a contest prep, but these hormones are also sometimes also used by individuals who are doing photoshoots or looking for an extreme body transformation. Specifically, T3 and T4 can help accelerate fat loss throughout a dieting phase, which is great; however, as with other compounds, many will take them without knowing much about how they work and what they do.

If this is you, please do not worry!! I have been in your shoes before, where I’ve blindly followed orders to get the end results. Therefore, the aim of this article is to discuss exactly what T3/T4 are, where they come from, and how the work within the body. The following article is written for informational purposes only and should not be deemed or taken as advice in any way.

Thyroid gland

If you weren’t already aware, T3/T4 are made and produced in the thyroid gland. This is a butterfly-shaped organ located in the base of your neck and is roughly 2-inches long. The hormones it produces help control your body’s metabolism, i.e., how your body uses energy. These hormones also regulate vital bodily functions such as:

-Menstrual cycle
-Body temperature
-Cholesterol levels
-Heart and breathing rate
-CNS and peripheral nervous system
-Muscle building and strength
-Regulate metabolism of carbs, fats, proteins
-Body weight

The thyroid gland uses iodine from our blood (consumed from our diet) to make T3/T4. However, the proportion of T3/T4 produced by the thyroid isn’t evenly split: in fact, a normal functioning thyroid’s daily output will be 20% T3 and 80% T4. As such, most of the T3 in our body comes from the conversion of circulating T4, as opposed to it being released from the thyroid. That conversion happens in organs such as the liver, skeletal muscle, and adipose tissue (fat tissue). Importantly, T3 influences the activity of all the cells and tissues in the body, and as such, can be understood to be the key hormone that regulates the speed at which your body’s cells work. Moreover, although more T4 is produced across the day, T3 is 3-4 times stronger, as it is the biologically active hormone (acts on cells/tissues). It’s effects are however “brief” due it’s short half-life (the time required for half the concentration of a hormone to be degraded).

In a natural individual, these hormones should never be too high or too low. If they are secreted in higher amounts, that individual would develop hyperthyroidism, meaning the body’s cells (and metabolism) work faster than usual. If they were secreted in low amounts, that individual would develop hypothyroidism, meaning the body’s cells (and metabolism) work slower than usual.

This is where I need to give you the more “sciency” stuff, but please stick with me, as it’ll all come together in the end!

The levels of T3/T4 in the blood are controlled by a delicate relationship between the thyroid, the hypothalamus, and the pituitary gland, called the HPT axis (Hypothalamic Pituitary Thyroid axis). The hypothalamus produces Thyroid Releasing Hormone (TRH) to tell the pituitary to produce more or less of thyroid stimulating hormone (TSH), which subsequently tells the thyroid gland to produce more of less of T3 and T4.

When T3/T4 levels are low in the blood, the pituitary gland will produce more TSH to tell the thyroid to increase the production and release of T3 and T4 into the blood stream. If the levels of T3 and T4 are high in the blood, the pituitary gland will produce less TSH, which will mean a slower production and release of these hormones from the thyroid gland. This effectively acts as a negative feedback loop system (Figure 1). This loop keeps the hormone levels within their ‘normal range’.

Figure 1

Now that we’ve gotten through that, you’re probably still wondering: “right Vaughan, how does that have anything to do with bodybuilders using T3/T4 hormones?”. Well, let’s look at what happens if this equilibrium of hormones is thrown off its normal balance.

Hypothyroidism and Hyperthyroidism

In the clinical condition of hypothyroidism, when the body isn’t producing sufficient levels of T3/T4, your metabolism, the cells in your body, and digestion all slow down. Hypothyroidism is an autoimmune disease, where the immune system of your body mistakenly attacks itself: in this case, the thyroid.
Signs of hypothyroidism include:

-low energy levels
-weight gain
-dry skin and hair
-joint/muscle pain
-sensitivity to cold temperatures
-frequent/heavy periods

Hyperthyroidism, on the other hand, occurs when the body is overproducing T3/T4. This again can be caused by an autoimmune disease, but in this instance, it causes an overactive thyroid as opposed to a slower one. This means that your metabolism, the cells of your body and digestion, all work at a quicker pace.

Signs of hyperthyroidism include:

-hair loss
-hand trembling
-sensitivity to high temperatures
-missed or light menstrual periods

Still with me, right?

Why would bodybuilders supplement this?

The thyroid is often seen to be the master switch in the body: if the dial is turned up just a little, everything speeds up, but turn the dial down, and everything slows down. This is the simplest way to look at it. Because of their direct relationship with metabolism, the hormones T3/T4 have a direct influence on the way fat is mobilised in the body. In other words, when there isn’t enough of them, individuals might find it very easy gain body fat, whereas when there’s a little more than is “needed”, you’ll find it very too easy to lose body fat.

Hopefully by now you can see the appeal in its use for bodybuilders who are looking to achieves extremely low levels of body fat. We know that when an individual diets to these extremes, the body’s metabolism will naturally slow down. This is because the body doesn’t like going to those low levels of body fat – at the end of the day, it only cares about survival and reproduction! – and therefore, it tries to conserve as much energy as it can, by slowing everything down. This includes the production of T3/T4, meaning that the individual cannot drop body fat at the same rates as it did earlier on in the diet. Simultaneously, digestion might slow, and one’s ability to add muscle mass (remember they are enhanced) will slow down too.

In addition to these hormonal and metabolic changes, we also know that as we pull more and more body fat off the body, stress increases simultaneously. The stress response produces higher levels of circulating cortisol in the blood stream throughout the day than we need, which adds to the difficulty of trying to drop body fat. Cortisol also directly slows down the HPT axis referred to earlier in the article.

It is for these main reasons that assisted bodybuilders will take exogenous T3/T4, as they know their body’s own natural ability to drop fat is downregulated the further they get into the diet, and the leaner that they get. It would take one far longer to get to the level of condition that is needed for bodybuilding shows with a slower HPT and a lower production of T3/T4, adding another reason for why one might want to supplement these hormones: with some preps taking 16-18 weeks, the thought of needing to diet for longer can seem unappealing to many.

Personal experience

Throughout every prep I’ve done, whether that was for a show or a shoot, I have used exogenous T3 and/or T4. 2017 was the only time I used T3 on its own, and at the time, that was simply down to following the instructions from my coach, who perhaps didn’t know the importance of using T4 alongside T3 at the time. From reading this article, you know that the thyroid’s daily output is 20% T3 and 80% T4, so if you’re going to go into supra physiological ranges of these hormones, it’s best keep that ratio in check.

Did I still get lean in 2017? Of course, but for every subsequent prep, I have used the combination of both hormones together. Did I notice much of a difference when it came to how I felt or the results I achieved? Well, it’s hard to say, because any time you diet to these extremes you feel terrible, and if you diet for long enough/hard enough, you always get lean. I have used the combination with clients, and it’s worked well over the years.

I’ve never noticed any adverse side effects when using these: of course, I used them for the accelerated fat loss and increase in metabolism, but I haven’t noticed anything else other than that. This might be different from person to person, but this is just my personal experience with it. I’ve spoken to some bodybuilders who’ve said that if they use too high of a dosage of T3, it leads to muscle wasting, which make sense, but then again, they could just use less.

I have also kept using T4 throughout the rebound periods after dieting and I’ve kept it in until my body has settled, before then dropping it and utilising a thyroid support for a month until its levels are back within normal ranges. This worked very well at helping control body composition as I pushed food and body fat levels back up post-show/shoot.

In summary, T3/T4 are hormones produced by the thyroid gland. These have a variety of roles within the body, but mainly control the body’s metabolism and cell activity. Low levels of both can lead to hypothyroidism, whereas high levels can lead to hyperthyroidism, and both conditions are caused by an autoimmune disease. Bodybuilders will often supplement these hormones when dieting for a competition or shoot to help them get down to low levels of body fat.

Vaughan Wilson Bsc Hons