T3 risk and side effects

Side effects of using T3

When used to treat hypothyroidism and in therapeutic doses, the side effects of T3 are practically nil, and the substance can be seen as something harmless.

However, it is not possible to transfer these characteristics when the hormone is used to achieve aesthetic changes, that is, in healthy people who want to raise their T3 levels above their natural levels.

Artificially raising T3 levels brings with it a range of benefits that will accelerate fat burning, but it comes with risks and side effects, such as:

Increased heart rateAnxietyInsomniaExcessive sweatingTremorsHeadacheIncreased bowel rhythmMenstrual irregularitiesLoss of muscle massSuppression of natural T3 productionRebound effectHeart failureIrritabilityRisk of overdose

The incidence and degree of these side effects may vary depending on the dose, time of use, pre-existing diseases and individual tolerance.

However, some of these side effects deserve special attention:

Cardiovascular side effects

The cardiovascular side effects of T3 require extra attention, as the hormone directly accelerates metabolism and, due to a series of factors, this also increases cardiac activity.

Therefore, side effects such as tachycardia (accelerated heartbeat), palpitations, increased blood pressure and arrhythmias may occur with use.

In predisposed individuals or those who already have an underlying heart condition, the use of T3 may worsen the problem, and may even progress to heart failure.

Loss of muscle mass

The loss of muscle mass with the use of T3 occurs because the hormone accelerates the metabolism as a whole, and this does not just involve burning fat.

When T3 levels are artificially elevated, the body enters a hypermetabolic state, where it uses more energy than normal.

It is worth remembering that the body does not obtain energy only from fats, but from all sources, such as proteins.

This includes the proteins within the muscles, which can be broken down and turned into glucose, which can then be used as fuel when the metabolism is revved up.

In simple terms, the use of T3 can favor both fat burning and the “burning” of muscle mass, especially if there is no well-defined strategy behind its use.

Additionally, T3 can directly reduce protein synthesis and increase muscle breakdown — especially in people who are not using anabolic steroids in conjunction, which in this case would generate a muscle-sparing effect.

Suppression of natural T3 production

Natural thyroid suppression occurs when the body, when receiving synthetic T3 (liothyronine), reduces or stops natural production.

This happens because the body understands that there is already enough hormone circulating, signaling the pituitary gland to reduce the release of TSH, the hormone that, in simple terms, stimulates the thyroid.

As a result, the thyroid gland will not return to normal function soon after stopping use, leading to a drop in natural T3 and T4 production.

In fact, it can take weeks for the body to return to normal thyroid function — or, in extreme cases, it may not recover at all, resulting in induced hypothyroidism, requiring ongoing hormone replacement therapy.

Risk of overdose

Unlike anabolic steroids, where abuse can occur over a long period of time and without causing noticeable symptoms until it is too late, T3 abuse can cause “immediate” overdose.

As we saw above, T3 use affects how the cardiovascular system functions, and its effects are dose-dependent.

This means that when used in very high doses, T3 can cause serious cardiac arrhythmias, hypertensive crisis and other effects that can have serious (and immediate) consequences.