In my last blog post (Got Testosterone?), I discussed the importance of testosterone and how it can be affected by various lifestyle, dietary, and environmental factors. Today I want to talk about a somewhat controversial topic. Namely, I will try to answer the question, “What is a normal testosterone level?”. Please note this article will specifically pertain to male testosterone levels. Testosterone in women is also quite important, and I talk more about female hormones HERE (**)
If you look at the reference range for total testosterone for men on a lab report from most labs in the US, you will see a range of somewhere around 300-1000 ng/dl. The numbers vary slightly because each lab uses their own testing population’s results to come up with a range. Then we also have to look at free testosterone, which is unbound active hormone. Total testosterone includes both free and bound testosterone. When testosterone is bound to carrying molecules, it is not able to bind to testosterone receptors to do its job. Since you can have a normal amount of total testosterone but a low free testosterone, it’s important to test both when treating for testosterone-related issues. Labcorp’s range for free testosterone is 8.7-25.1 pg/ml.
Now we might assume that as long as our numbers are within the reference range, they are good. However, there are some issues with that conclusion. First of all, we need to understand where the reference range comes from. Before I went to medical school, I was under the mistaken assumption that all lab values were based on correlations with disease or health outcomes. I thought that the lower limit of a reference range on a lab test was chosen because more disease was seen below that number, and similarly for the upper limit Although this is the case for some lab tests, such as cholesterol and blood sugar, it is not the case for most lab markers, including testosterone.
Instead, to create a reference range, a lab will look at all the lab values it’s been collecting for a population for that given marker (in this case, total testosterone). They then determine what range of values will include the results seen for 95% of the entire population tested. Thus, 2.5% of the tested population will have testosterone values ABOVE the reference range, and 2.5% of the tested population will have testosterone values BELOW the reference range. There is nothing in this reference range-setting methodology that seeks to find at what levels signs or symptoms of disease occur – i.e. we do not have direct evidence that correlates disease with being outside of the reference range or health with being inside the range. It’s just designed to normalize the values for 95% of the population. So, it is entirely possible that disease or sub-optimal health could occur in large numbers of people due to their having levels for some lab that are not actually healthy or optimal, yet they are still technically in-range. Just because 95% of a population has certain lab values, doesn’t mean that those values are the healthy values. What if the majority of the population tested is stressed, exposed to toxins that depress their testosterone levels (see here – link to ‘Got Testosterone’), and overweight – all things which are, unfortunately, exceedingly common in our population?
This methodology isn’t without merit, since for many tests in general, we often will see more disease when lab values are outside the reference ranges and less disease when labs are inside the range. However, not infrequently, the reference range will be problematic. What if, for example, the values of testosterone were dropping for some unknown reason in the population of men tested, such that each year the test results got lower and lower? In that case, the laboratory would see lower values across the board, and then when they update the reference range, they base it on these ‘normal’ yet declining values. So then what was previously considered a low testosterone level would now be considered normal! This is precisely what has been occurring with testosterone levels, as you’ll see below.
A large study looking at testosterone levels in men in Massachusetts from 1987 to 2004 found a population-wide decline in testosterone levels that was not associated with age, nor with health and lifestyle factors known to be associated with lower testosterone levels. The study found that men in 2004 had a 17% lower level of testosterone than those of the same age in 1984. Looking at men of the same age over the years studied, the average drop in testosterone was 1.2% per year. Interestingly, the difference in testosterone between different age groups tested in the same year was much less than the difference seen in those of the same age group over time. In other words, men age 70 in 1985-87 had only 6% less testosterone than men age 45 in the same time period. Yet 60 year old men in 2002-2004 had 13% lower testosterone levels than 60 year old men in 1985-87. (1) Thus we can presume there is something causing a precipitous decline in testosterone levels in the population. The larger issue at stake is the associated decline in sperm count and fertility rates, which are both affected by testosterone levels. (2)
I discussed some of the causes of low testosterone HERE. Although we have identified some of the chemicals we are exposed to that are associated with testosterone decline, these are likely not all of them, as there is quite a lag time between introduction of new chemicals into the environment and the recognition of potential negative effects on our physiology. The take-home message is we need to be more conservative and thorough In our vetting of new chemicals before deciding to allow them to be placed in our air, water, soil, and food supply.
So if we cannot rely on the reference range to determine ideal testosterone levels, what CAN we use to determine ideal testosterone levels? There are some doctors who are using a studies to justify a target of near 1000 for all patients. However their reasoning is flawed, and they are cherry-picking which studies to look at. One study showed that testosterone levels seemed to be directly proportional to mortality from all causes – i.e the higher the testosterone levels were within the normal range, the less death occurred – from any cause. It showed a 41% reduction in risk of death in those with testosterone in the highest quartile when compared with those in the lowest quartile (3). Furthermore, a meta-analysis of 12 studies showed that low testosterone levels conferred a 35% greater risk of death (4). However, we do not know if the people with low testosterone were more likely to have OTHER factors that were the cause of an increase in death. This is a common error in interpretation of research findings – mistaking a correlation for causation. We thus do not know if increasing testosterone to such a high level (1000 ng/dl, which is the very top of the current range on lab tests) is necessary to normalize the risks. However, we do know testosterone exerts proven benefits on blood sugar, libido, muscle and bone mass, mood, and cardiovascular health. We also have seen in one study of diabetic patients with testosterone deficiency that those given testosterone replacement had a significantly reduced risk of death (5). Finally, another study has shown increased mortality at LOWER levels of testosterone, but no association with mortality at higher levels – this means that if it’s too low it can increase mortality, but once it gets to a certain threshold, there may be no further decrease in mortality. Other studies show that intermediate levels of free and total testosterone are associated with the lowest risk, and levels above and below this were associated with elevated risk (4).
Thus we can clearly see a benefit to getting testosterone to AT LEAST what’s considered the current normal range (i.e. above 300 ng/dl). As an integrative naturopathic doctor, I recognize that not everyone is the same, and thus we need to treat people based on the whole picture – including looking at labs other than testosterone alone, as well as how the patient responds to treatment. This information helps guide our testosterone dosing and target lab levels. I help my patients raise their testosterone levels using a combination of lifestyle, diet, detoxification, and testosterone replacement therapy. I don’t have an exact number I aim for, as different men will respond best to different levels. If we have records of the patient’s own testosterone levels at a time they were most apparently healthy, this may help define the target level. Using the testosterone level as a starting point, I also take into account other lab values as well as the patient’s symptoms, in order to determine individualized treatment goals.
I hope this article gave you some more understanding of the complex topic of testosterone levels. If you would like to find out about further assistance with your hormones or other health issues, you can contact us to set up a free 10 minute phone consultation. Our number here in Sherman Oaks is 424-278-4325.
Yours In Good Health,
Dr. Fischer
References:
Travison TG, Araujo AB, O’Donnell AB, Kupelian V, McKinlay JB. A population-level decline in serum testosterone levels in American men. J Clin Endocrinol Metab. 2007 Jan;92(1):196-202. PMID: 17062768
Swan, SH, EP Elkin and L Fenster. 2000. The Question of Declining Sperm Density Revisited: An Analysis of 101 Studies Published 1934-1996. Environmental Health Perspectives 108:961-966.
Khaw KT, Dowsett M, Folkerd E, Bingham S, Wareham N, Luben R, Welch A, Day N. Endogenous testosterone and mortality due to all causes, cardiovascular disease, and cancer in men: European prospective investigation into cancer in Norfolk (EPIC-Norfolk) Prospective Population Study. Circulation. 2007 Dec 4;116(23):2694-701. Epub 2007 Nov 26.
Shores, Molly. The Implications of low testosterone on mortality in men. Current Sexual Health Rep. 2014 ec 1; 6(4): 235-243. Published online 2014 Sep 24. doi: 10.1007/s11930-014-0030-x. PMID: 25685109
Muraleedharan V, Marsh H, Kapoor D, Channer KS, Jones TH. Testosterone deficiency is associated with increased risk of mortality and testosterone replacement improves survival in men with type 2 diabetes. Eur J Endocrinol. 2013 Oct 21;169(6):725-33. doi: 10.1530/EJE-13-0321. PMID: 23999642