T Nation

Does TRT Lower Thyroid Production?


I am under the impression that TRT will shut off thyroid signaling hormone in the testes and thus lower free t3/t4 levels ? Is this accurate? And if so would that mean thyroid hormone is necessary to use along with TRT in order to maintain thyroid health? Thnks



Please link to your sources.

But we do see a lot of guys here with thyroid problems that pre-date their TRT.

Please see the thyroid basics sticky.


Thanks for the reply.I’ve read all of the stickies and many of your posts,been a lurker for many years. The link you requested cam from Dr Marianos forum, it is pasted below

Libido - Dr. Mariano’s thoughts on Signaling changes after developing hypogonadism

From Dr. Mariano’s forum…

Signaling changes after developing hypogonadism

If a male is hypogonadal for an extended period of time, then the first exposure to testosterone replacement can be exhilarating. Then it eventually goes away.

Here is a simplification of what may be happening:

Testosterone increases dopamine signaling in the brain. Dopamine signaling promotes sex drive, attention, interest in activities, elevates mood, and is calming in effect since it also reduces norepinephrine signaling. Without testosterone, there may be an increase in dopamine receptor concentration due to the loss of dopamine signaling.

Testosterone, itself, has a calming effect on the brain. It helps reduce norepinephrine signaling. Losing testosterone loses another of the control signals on norepinephrine production.

The loss of testosterone production is also accompanied by a loss of testicular thyroid releasing hormone production. This results in a reduction in thyroid hormone production. This results in a reduction in metabolism and energy. The brain compensates by increasing norepinephrine production to increase energy. This increase in norepinephrine signaling can promote insomnia, irritability, anxiety. It also does not usually improve energy well.

Over time, with aging, thyroid hormone production is reduced. This compounds the problem of thyroid loss accompanying testosterone production loss, including a further increase in norepinephrine signaling to compensate for the loss.

Testosterone, overall, is an anti-inflammatory signal and helps govern adrenal function, preventing excessive production of cortisol. Without testosterone, under increased norepinephrine signaling levels, high cortisol production may occur - which may or may not cause problems.

The elevated norepinephrine signaling may then be accompanied by pro-inflammatory cytokine signaling as the brain becomes chronically elevated by stress signaling/norepinephrine. Over time, this may then cause hypothalamic-pituitary-adrenal dysregulation with low cortisol production.

Estradiol, functioning as an MAO, increases serotonin greater than norepinephrine. It promotes competitiveness, drive, sex drive, aggressiveness. Without testosterone, however, and the dopamine increase it promotes, Estradiol would tend to flatten sex drive and promote irritability and aggression, anger, instead. Unless testosterone production is very low, Estradiol can be maintained since so little in relationship to testosterone, is needed in men. The relative change in signaling strengths of each poses problems of excessive estrogen. This includes increased thyroid binding globulin and reduction of free thyroid hormone signals. Excess estrogen, by increasing serotonin excessively, may reduce sex drive.

Norepinephrine is important for sexual function. It promotes the high and excitement that accompanies sex drive / libido. But in excess, it does not. It causes tension, stress, distress, anxiety, irritability, which lowers sex drive. To increase norepinephrine, the brain may reduce serotonin, GABA, then dopamine production - causing problems with deficiencies in serotonin, GABA and dopamine.

Excessive norepinephrine production also causes insulin resistance. The increase in insulin production that results is pro-inflammatory. It also further reduces testosterone production. Insulin also promotes fat storage. The resulting increase in fat results in an increase in Leptin and other pro-inflammatory signals from fat cells.

And so on and so on. These are some of the changes that permeate the system from the loss of testicular testosterone production. Some are added to by changes in the metabolism of the other cells which produce other signals such as thyroid hormone, through the process of aging or with nutritional problems or with genetic predisposition to other signaling or metabolic problems or through structural changes such as the loss of cells in the hippocampus and other brain structures.

So what happens when testosterone is replaced?

There is a reversal of some of the initial signaling problems.

Because there is a larger number of dopamine receptors from the dopamine signaling deficit caused by the loss of testosterone, there is dopamine supersensitivity to the surge of dopamine signaling that accompanies the increase in testosterone with replacement. This can cause a high - with heightened sex drive, alertness. and an elevated mood.

Testosterone would also free up thyroid hormone by reducing thyroid binding globulin, reversing estrogen’s effects, improving function from this angle. This would improve energy

Testosterone would then reduce excessive norepinephrine signaling, which as it comes more in normal physiologic strength, helps dopamine in providing a higher level of libido, sex drive, and an emotional high.

The testosterone to estrogen ratio would improve, reducing effects of excess estrogen. Insulin signaling is reduced. The body becomes less in an inflammatory state.

The person feels better, if not feels a high from the initial treatment with testosterone.

Over time, however, with increased dopamine signaling, dopamine receptor production is reduced back to a normal amount. Dopamine, as the reward signal, the feel good signal, can’t be elevated for a prolonged period of time excessively, without problems occurring. It no longer becomes a reward signal if it is elevated for a prolonged period of time. Tolerance, through receptor reduction, occurs.

After the initial high, other problems also occur.

Exogenous testosterone suppresses testicular thyroid releasing hormone production. This reduces thyroid hormone production, undoing the initial increase in free thyroid hormone that testosterone caused. If there is hypothyroidism in the first place, this exacerbates that problem.

If there are other neurotransmitter, hormone, cytokine signaling problems or metabolic-nutritional problems outside of hypogonadism, these may complicate or undo what testosterone initially did.

If the man aromatizes testosterone to estrogen excessively, problems with excessive estrogen occur. If aromatization is not enough, then problems with too little estrogen occur. In either case, sex drive is impaired.

Thus, the hypogonadal man returns to Earth. And the initial high is lost.

The situation isn’t totally negative.

As long as one attempts to optimize the entire system, then testosterone will generally have a good effect on libido to one’s satisfaction.

If a good amount of testosterone in men - 650 ng/dl - is present and problems remain, then there is more work to be done on the rest of the system to improve function.

Generally, it is very difficult to maintain the testosterone high and very high level of libido as seen in the teenage years. Enough dopamine neurons, for example, may have died off as a result of agin, to prevent full return to a high state.

It is highly important to optimize nutrition to improve function. This may entail more meats and saturated fats in the diet, for example.

Keeping testosterone at fairly flat levels may help, since peaks of testosterone may result in reduction in dopamine receptors and an increase in dopamine reuptake transporters. Keeping testosterone at flat levels may require more frequent dosing. The extreme flat dosing is achieved via testosterone pellet placement.

Once as many factors are addressed, one can then look to see if growth hormone replacement is needed. This may further increase libido in some people.


In my case I’ve been on TRT for nearly 2 years
150 MG in divided doses (experimented with 2x a week up to 7x a week)
Arimidex 1-2 mgs per week in divided doses (I am estrogen dominate)
HCG 250 IU 3x a week

Recently I had a thyroid test done as I’ve suspected symptoms of low temps in morning (under 97) sparse outer eyebrows difficulty losing fat lack of libido and overall energy were related thyroid…labs revealed:

Free T3 2.2 Standard= 2.3-4.2
Free T4 1.4 Standard = 0.9-1.8
TSH 1.70 Standard = 0.27-4.20
Rt3 I do not have that number but it was low not high and not normal

I was using 600mg of EQ and 60 mg TBOL at the time of this test along with my typical TRT dose. if these drugs impact thyroid I can find no proof of in terms of studies. Many feel they do not while a few feel AAS can and will impact thyroid function including DR Mariano…

My doctor of course looked at my TSH and said I was fine and not to worry about the low T3…At this point im considering retesting thyroid values since I’m off the EQ and TBOL and back to just TRT to see if T3 has improved since coming off even though my symptoms have not subsided…If not im considering self medicating with T3.Still on the fence about this however.Any advice is appreciated… Thnks


“The loss of testosterone production is also accompanied by a loss of testicular thyroid releasing hormone production. This results in a reduction in thyroid hormone production. This results in a reduction in metabolism and energy.”

For that to be true, the function of hypothalamus+pituitary+thyroid would have to be broken and not have a functional feedback loop; which is not valid.


Ksman - So TRT isn’t a cause for low thyroid in your opinion

My thyroid panel has my TSH and t4 both normal while my t3 is low (1 point under the average) Two tests have confirmed this…My body temps are consistently in the low 97 degree range which leads me to think I have some kind of thyroid problem or at least a t3 conversion problem…im wondering if one possible cause for this is low conversion in the liver? Ive taken various oral steroids and in fact was taking them at the time of this test…Is it possible they could have decreased my liver function and also impaired t3 conversion? Or am I on the wrong track? Any thoughts or opinions are appreciated.


There are studies that show HCG can act like TSH and stimulate the thyroid. Of course most studies are with women. I’ve heard of TRT helping thyroid, but not hindering.

How is your E2 level? When my E2 is high, my morning temperatures are 0.5 degrees lower. I stopped taking thyroid meds when I finally got my target E2–it was a bigger metabolism driver than my thyroid.

Have you checked out stopthethyroidmadness.com? Lots of good info there on throid conditions. If it is a T3 conversion issue, here are some things that can help:


Thanks for the reply…I keep e2 in check with adex and or nettle root…I have issues with finding the sweet spot however as often I drive it too low…I’m on hcg 250 EOD…I wonder if the body temp issue is over rated? I read the link you posted on t3 to t4 conversion …going to try some of those remedies and then retest …I’m hoping its a liver conversion issue …