Understanding Low Testosterone: Signs, Symptoms, and Diagnosis

This video discusses the topic of low testosterone and the importance of proper testing and diagnosis before initiating testosterone therapy. It explains where testosterone is produced in the body and what constitutes low testosterone levels. The video also explores the signs and symptoms associated with low testosterone and emphasizes the need for clear expectations when starting testosterone replacement therapy. It highlights the goals of therapy and the importance of follow-up and monitoring. The video concludes by promoting an online learning platform and presenting a challenge question unrelated to the topic.

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Key Insights:

  • Up to 25% of males receiving testosterone therapy did not get an initial testosterone test to determine their levels.
  • Testosterone is primarily produced in the testes by cells called interstitial cells of Leydig.
  • Normal range for total testosterone in males is between 300-1000 nanograms per deciliter.
  • Low testosterone is diagnosed with two separate tests showing low levels, along with the presence of signs and symptoms.
  • Signs and symptoms of low testosterone include reduced lean muscle mass, obesity, reduced energy, diminished work performance, decreased libido, etc.
  • Testosterone replacement therapy aims to raise testosterone levels to about 450-600 nanograms per deciliter while improving signs and symptoms.
  • Follow-up and monitoring of testosterone levels is crucial for effective testosterone replacement therapy.


Testosterone is an amazingly powerful hormone with multiple functions and now more than ever you’ve probably heard people talking about Low T or low testosterone and just testosterone clinics popping up everywhere but let me give you this interesting piece of information there are studies that estimate that up to 25 percent of males that have been receiving testosterone therapy never even got an initial testosterone test to see what their levels were at so how would you even know if you had low testosterone in that situation well in today’s video we’re going to actually talk about what constitutes low testosterone what happens to the body with low levels so the signs and symptoms that people might experience with low testosterone and of course the main goals and the whole point of why we might initiate or start someone on testosterone it’s going to be a hormonal one so let’s do this so let’s start with where testosterone is produced testosterone is produced in these amazing structures called the testes and you are looking at a very close-up view of one testis the right one to be exact and you can notice these string-like structures and these are called seminiferous tubules now the seminar first tubules actually produce sperm they don’t produce the testosterone but in between these tubules are clusters of cells called the interstitial cells of lighting or sometimes just called lighting cells now these lighting cells actually make up about 20 percent of the overall mass of the testes and these are the cells that produce testosterone now we should note that other androgens which are hormones that have masculinizing effects and testosterone being the main Androgen are produced in other areas of the body such as the outer portion of the adrenal gland called the adrenal cortex and this is actually where females can get some androgens however this is a very small amount when we compare it to the amount produced by the testes for example in males the androgens secreted are produced by the adrenal cortex accounts for less than five percent of the masculinizing effects and in females it pretty much causes no major masculine characteristics except for contributing to the development of pubic hair and axillary hair which is a fancy pants way of saying armpit hair so what constitutes low testosterone well a pretty good place to start would be what are the normal ranges so if we were to do like a total testosterone test on a male we would see that the normal range is pretty broad would actually be anywhere from 300 nanograms per deciliter up to a thousand nanograms per deciliter now there might be some subtle variations depending on which lab does the test as far as those numbers but for the most part 300 to a thousand nanograms per deciliter with females as an FYI it’s much lower it’d be 15 to about 70 nanograms per deciliter so you might think anything below 300 in a male would can be considered low testosterone and that actually is the number or the cutoff that the AUA uses which is the American neurological Association for saying low testosterone anything below 300 at least from the testing standpoint and the reason I stress that is because this is really important there is more to low testosterone than just the numbers having a number of 300 nanograms per deciliter all by itself is not enough to diagnose someone with low testosterone there are more criteria that need to be met first you actually have to have two test results that show low testosterone and these tests need to be done on separate days and ideally they’re done in the morning now the reason why it’s more ideal to take the testosterone levels or do the testing in the morning is because testosterone levels have what’s known as a diurnal variation or in other words the levels fluctuate throughout the day with the highest level levels being at about 8 am now we do need to mention or at least specify that this variation in testosterone levels throughout the day is much more prominent in younger males because as males age that variation of the testosterone levels throughout the day becomes less and less and you can really see this from this little whiteboard chart with the blue line showing how it varies with younger males and that Peak at 8 AM whereas the red line shows how it varies less and less with the older males so admittedly taking the levels in the morning does become less important as males age however many of the medical associations still tend to recommend doing the testing in the morning to help maintain consistency of timing and to help minimize any possible variation that could take place but now that we’ve gone over the ranges and the variation what else do we need to officially diagnose someone with low testosterone and this next part is very important to this diagnosis yes we need the two tests showing low testosterone levels plus the person needs to to be experiencing signs and symptoms that are associated with low testosterone and these signs and symptoms can be quite the list and this list includes physical signs and symptoms reduced lean muscle mass obesity reduced energy and fatigue reduced endurance diminished work performance diminish physical performance loss of body hair reduced beard growth cognitive signs and symptoms depression cognitive dysfunction reduce motivation poor concentration poor memory irritability sexual signs and symptoms decreased libido and reduced erectile function so as you can see having even just a few of these signs and symptoms wouldn’t be much fun at all and it’s also important for us to point out that if we go back to this list that these signs and symptoms are not just exclusive to low testosterone you could look at this list and say man I’ve experienced a handful of these signs and symptoms throughout my life and so in other words there are other potential causes to these signs and symptoms and why it’s also so important for us to not just be all willy-nilly with giving people testosterone and just blaming all of our signs and symptoms on low T if you will but yes it is justifiable if somebody meets the diagnostic criteria of those two low testosterone tests plus the signs and symptoms to initiate testosterone replacement therapy but even then it’s still important to have clear expectations and I do this with my patients one actually came in the other day where we did a lot of these tests and the expectations are hey if you’re going to take testosterone replacement therapy and you meet these diagnostic criteria you still have to understand that it’s not necessarily going to fix all of these issues and so that’s where I think we need to go to the next step here and talk about the goals of testosterone replacement therapy and that will help us to understand who should stay on the testosterone versus who maybe should come off of it even if they initially started the testosterone because of meeting this diagnostic criteria according to the AUA the American neurological Association the target range for testosterone therapy is to use the lowest dose possible while getting somebody up to about 450 to 600 nanograms per deciliter and that range can be a little bit hotly debated in some circles and we can get into that a little bit later but the AUA for the most part knows their stuff and so it’s a pretty good range to start with now remember this is not just to raise the levels just for the sake of raising the levels it’s raising the testosterone in combination with an improvement in the signs and the symptoms because there are situations where if somebody got their levels up to 450 to that 600 range and they had no improvement in their signs and symptoms the data shows that it’s a pretty good chance that testosterone is not really the problem or the cause of their symptoms and in that case the AUA actually recommends that that person should discontinue taking the testosterone again not to just take it for the sake of having higher numbers and I do want to go back to that part where I I mentioned there can be a debate around that target range for testosterone specifically around that upper limit of 600. is there ever a reason to go higher than that 600 upper limit recommended by the AUA let’s say we had somebody who got some improvement getting to around 600 but then their levels got up to like 700 or maybe even a little above and they continued to have Improvement so those are those situations where you think okay maybe in a case-by-case basis it might make sense to go higher than that initial recommended range of 450 to 600. although most people if they haven’t experienced again any Improvement in that range probably not going to be the testosterone that’s causing their symptoms but this is why it’s also again so important to be working with a clinician so that you can monitor the response to therapy which kind of takes me to a little bit of a soapbox and that is the importance of follow-up there is data that suggests that after being initiated on testosterone therapy nearly half the men and do not follow up to get their levels drawn again now we’re not going to be judgy here because yes we understand life can get in the way things come up Etc but you can’t expect to be very effective with testosterone replacement therapy or any hormone replacement therapy for that matter if we’re not monitoring the levels to see how our bodies are responding do you need a dose adjustment do we need to raise it do we need to lower it are the symptoms improving this follow-up will truly help guide the continuation of the treatment so hopefully that gives you a good Baseline understanding about testosterone levels and the approach to initiating therapy but I do have one more question for you a problem you could help me solve what if you had a very large tank and to the left of it there’s a 10 kilogram toy car in a separate tank that is 1 20th of the radius of the larger tank how much mass can the 10 kilogram toy car hold in the larger tank while the water levels are even is it 10 kilograms 40 kilograms 400 well you can find the answer to this by visiting this sponsor of today’s video brilliant brilliant.org is an amazing interactive online learning platform for stem subjects it’s one of the best ways to learn math science and computer science I personally use brilliant steel to this day and I find it fun and interactive yet challenging enough to keep my attention and some of my favorite courses are the ones on scientific thinking which is actually where you can find the answer to that toy car question that we just post brilliant is also constantly adding new lessons each and every month so you will definitely find something for you regardless of where you are on your educational Journey so if you’re interested go to brilliant.org Iha to get a free 30-day trial plus the first 200 people we’ll get 20 off their annual subscription and when you do find the answer to that car question go ahead and post it in the comments below as well as let us know what you thought of the video I also want to let everyone know if you want more information on testosterone we did a video earlier where we talk about all of its amazing effects on the human body and we’ll link it here as well and if you feel need like And subscribe and of course we’ll see in the next video foreign