T Nation

HPTA - Friend or Foe


This one's for the older guys.

Hypothalamic Pituitary Testicular Axis (HPTA) is the name given to the system of organs that regulate testosterone production in men. For women, the counterpart is the Hypothalamic Pituitary Ovarian Axis (HPOA). (There are many other hormone systems are regulated in a similar fashion.)

The hypothalamus controls many daily hormonal cycles, including the daily testosterone cycle. It receives signals and stimuli from throughout the body and then co-ordinates the function of other organs by releasing various neurohormones. One of the neurohormones released by the hypothalamus is Gonadotropin-releasing hormone which stimulates the pituitary to release Luteinizing-hormone (LH) and Follicle-stimulating hormone (FH). LH signals the testes to produce testosterone.

Obviously, this is an extremely shortened version of things and there's a lot more going on, but it's enough to give you the big picture and to remind you that your body is a very complex system and that nothing happens in isolation. Hormones are a complex dance of stimulus and response and getting a handle on them isn't impossible by any means, but it does require a certain commitment to study.

So, in short, the HPTA regulates testosterone production. (It also regulates estrogen production but more on that later)

When we're younger, a properly functioning HPTA maintains relatively high levels of testosterone and relatively low levels of estrogen. However, as we age, these levels tend to shift. Testosterone goes down and estrogen goes up.

It's important to understand that this is perfectly normal. We're designed to wither away and die and this shift in the hormone balance is part of that process.

However, if you're like me, you might be willing to say "fuck natural" and do something to fight this natural process.

Obviously, proper diet, good training, and a healthy lifestyle are a huge part of any anti-aging regimen and nothing I'm talking about here replaces the need for those important steps. Eat right, train right, stay lean and you'll be miles ahead of the general population even if you do nothing more.

But there is something you can do to trick your HPTA into being your friend instead of your foe.

Here's how it works...

It all starts with the idea that your properly functioning, but older, HPTA thinks that it should maintain relatively low levels of testosterone and relatively high levels of estrogen.

Left unchecked, this is not such a good thing, but by understanding the process, we can use it to our advantage.

Estrogen is produced in two ways. Primarily it's produced by the conversion of testosterone.

That's worth saying again... estrogen is made from testosterone.

This is done with the help of an enzyme called aromatase. Aromatase binds to testosterone and converts it to estradiol. This is the key to this whole approach, so get that locked in.

Our bodies make estrogen by FIRST making testosterone and then using aromatase to convert it to estradiol.

Ok, so aromatase is obviously pretty important stuff.

Remember our friend the hypothalamus? He's also controlling aromatase production, so you can see how important the HPTA is to all of this.

The second way that our bodies make estradiol is in body fat cells... so get lean and stay lean.

Ok now we're ready for the real deal.

Since your HPTA is trying to maintain relatively high levels of estradiol, if your estradiol levels go down, your HPTA will try to "fix" that by pumping out more testosterone and more aromatase and using them to get those levels back up.

Think about that for a minute.

Lowering your estradiol causes your testosterone to go up... and it does this "naturally."

In other words, you can trick your body into making more testosterone if you can somehow lower your estradiol. The catch is that if you don't also control aromatase, then your extra testosterone is just going to be attacked by aromatase and converted into estradiol and you're back where you started.

Here's the beauty of it all.

If you take an aromatase inhibitor (AI), then that inhibitor will bind to the aromatase enzyme and render it useless. By lowering aromatase levels, you slow down the conversion of testosterone to estradiol and so estradiol levels go down.

Your HPTA senses that drop and tries to fix it by pumping out more testosterone. But since you're controlling aromatase by taking an AI, that extra testosterone can't be converted to estradiol and your testosterone levels go up and stay up at the same time that your estradiol levels go down and stay down! SWEET!

So by understanding how the HPTA functions, we can see that controlling aromatase is actually the key to regulating both testosterone and estradiol. Aren't you glad you decided to try and understand this stuff?

Natural Testosterone Boosters

Most herbal "testosterone boosters" are actually aromatase inhibitors. Don't forget that however they work, they have to work within the confines of your natural systems since none of them are testosterone itself. So if you want to fool around with herbal supplements, read the labels and check the contents to see if any of the ingredients are known aromatase inhibitors. Even some foods (like broccoli) are known to have aromatase inhibition properties.


But let's face it, most herbals are expensive and produce very limited, if any, effects. If you want the real deal in aromatase inhibition, you need to take drugs. The big three are anastrozole (Arimidex), letrozole (Femara) and exemestane (Aromasin). They're all aromatase inhibitors but they work in different ways so it's important that you read about and understand all three.

All three are also available without prescription as research chemicals.

I'm not going to go into detail about these drugs or how to use them exactly because I don't want you to think I am telling you to take them.

In fact, I'm specifically telling you DO NOT TAKE THEM... Unless you educate yourself and understand the risks involved. Estradiol is needed for health and blindly taking an AI can lower estradiol to unhealthful levels if you're not careful.

But AI's do represent a very real way to raise testosterone levels safely without resorting to Testosterone Replacement Therapy. .. if you know what you're doing.

Now don't forget that all of this is dependent upon you having a properly functioning HPTA . In other words, if your testicles for some reason aren't capable of making testosterone in the first place (primary hypogonadism), none of this is going to get you anywhere. If your HPTA is messed up (secondary hypogonadism) and not regulating things properly, then this won't work. But if you're "normal" and your testosterone levels are low but not low enough to qualify for TRT, this may be a real help. Check it out.

You should also be aware that there are studies that say this approach doesn't work or if it does work, it doesn't improve quality of life. Get educated and decide for yourself. I've tried it and it worked for me. My testosterone went up by almost 100 points and my E2 went down by 30 points and I noticed a significant increase in sexual and athletic performance. I wouldn't talk about it if I hadn't tried it. One guy's experience is not a scientific study but I know I'm not alone in my results.


I am not a doctor and this is not medical advice. This article was written only for information purposes. If you put powerful chemicals in your body and it all goes bad, don't blame me. Be smart and be safe. But also educate yourself and you may find that you can significantly improve the quality of your life.

Look around on the net. Lots of guys have written excellent articles about all of this and I'm encouraging you to find as much information as possible before you decide on any course of action... even if it is doing nothing and letting nature take its course.



This post was flagged by the community and is temporarily hidden.


Ah, but you are not alone in your experience: it does work, and there are lots of studies that AIs alone do work to normalize T levels in aging or obese men.
(And sick people, in various situations. And we do not know a lot about the down side in men...yet.)

Now, then, where is Buffed Samarai when we need him?....


"Amused K-9", You are the dog, Dog!....


Damn straight it should!...Mods?....


Was sure interesting.


Thank you for taking the "mystery" out of it for so many. I too am one the VERY happy campers whose quality of life is improved by the addition of an AI.
I have a doctor's prescription for Arimidex, which also means I have access to blood tests. I keep a close eye on not only how I feel, but I do the blood tests as a "fail-safe" in case I miss something.

Can using a small amount of an AI have a huge change in your QOL? Possibly. Can a small amount of an AI make your life hell too? Possibly. I asked the same question twice on purpose...
AI usage has to be very closely monitored, and if you're new to the whole business of "do I need HRT/TRT or not?" Don't jump on the hearsay wagon. Do a LOT of research. Read other guy's posts too.
Just to clarify:
I have one friend that takes 0.10 mg's a week of Arimidex and his life is good. If he takes anymore, he suffers.
I have another friend that takes 3.50 mg's a week of Arimidex, because if takes any less he suffers.
So please be rational when contemplating the self-prescribing of this family of drugs okay?


That is a great warning. The one guy is taking 35 times the amount the other guy is taking and both are are the edge of the appropriate dose.


The low dose amounts are easily explained by those who are adex over responders. The high doses are not easily explained.