Published June 20 2016
Testosterone is a sex hormone that is produced by the testicles in men and ovaries in women. It is considered to be a male sex hormone, although a deficiency of testosterone in females can also cause problems. In this article I’m going to discuss some of the more important functions of testosterone, list some factors which can cause a decrease or increase in this hormone, and I’ll of course discuss how it relates to thyroid health. I’ll also talk about testing for this hormone, and how to correct a testosterone deficiency without taking bioidentical testosterone.
All of the sex hormones are derived from cholesterol. So what happens is that cholesterol forms pregnenolone, which in turn divides into two separate pathways. One of these pathways leads to the formation of progesterone, and ultimately cortisol. The other pathway leads to the formation of DHEA, which in turn converts into androstenedione, and this in turn converts into testosterone. And testosterone can convert into estradiol or dihidrotestosterone (DHT). It’s nice to have a basic understanding of the hormone pathway, as if someone has very low cholesterol levels, or a pregnenolone or DHEA deficiency, then this in turn can cause a testosterone deficiency. In addition, since testosterone is a precursor to estradiol, if testosterone gets too high (i.e. from taking DHEA or bioidentical testosterone), then this can lead to high estradiol levels, and a condition of estrogen dominance.
In males, testosterone is mainly synthesized in Leydig cells, which are regulated by the pituitary hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH). So the production of testosterone is regulated by the pituitary gland, which in turn communicates with the hypothalamus. As a result, if someone has dysregulation of their hypothalamic-pituitary-gonadal (HPG) axis, then this can affect the production of testosterone. When testosterone is transported through the blood it mostly binds to sex hormone binding globulin (SHBG), although it can also bind to another transport protein called albumin. If someone has low levels of SHBG this usually means that they have higher levels of free testosterone, whereas if they have high levels of SHBG this usually means they have lower free testosterone levels. I spoke about SHBG in greater detail in a separate article entitled ” The Facts About Sex Hormone Binding Globulin and Thyroid Binding Globulin “.
In premenopausal women, about one quarter of testosterone is produced in the ovaries, while another 25% is produced by the adrenal glands. The remaining testosterone is produced by peripheral conversion. So when women are in postmenopause, the ovarian production of testosterone will decrease, but remember that 75% of testosterone production comes from other areas in women.
What Are The Health Benefits Of Testosterone?
Testosterone has many important functions. Most people reading this probably know that testosterone is necessary for the development of male reproductive organs, as well as secondary sexual characteristics. However, there are numerous other functions of testosterone:
Increased muscle mass. Testosterone helps to increase muscle mass by increasing protein synthesis (1) (2) (3). Many people with hyperthyroidism have a decrease in muscle mass, and so when someone with hyperthyroidism or Graves’ Disease experiences a decrease in muscle mass it probably is due to the thyroid hormone imbalance, although it still might be worth measuring the testosterone levels.
Cognition. A few studies suggest that low levels of testosterone may be related to cognition, and that increasing testosterone levels may help to improve cognition (4) (5). These same studies have also mentioned how testosterone levels have been shown to be lower in those with Alzheimer’s disease. However, cognition is also commonly affected in thyroid and autoimmune thyroid conditions, especially with Hashimoto’s Thyroiditis, although it can occur with hyperthyroid conditions. But if someone has cognitive impairment and low testosterone then this is something that should be addressed.
Insulin sensitivity. Numerous studies have shown a relationship between low levels of testosterone and insulin resistance and type 2 diabetes (9) (10) (11). And these studies also show an improvement in insulin sensitivity as testosterone levels are increased. It’s worth mentioning that polycystic ovarian syndrome (PCOS) is characterized by elevated free testosterone levels, which are a result of high insulin levels. I spoke more about PCOS in an article entitled “PCOS and Thyroid Health”
Symptoms of Testosterone Deficiency:
These are some of the more common symptoms of a testosterone deficiency (15):
- Decreased libido
- Vasomotor instability
- Decreased bone mineral density
- Erectile dysfunction
- Reduced muscle strength/mass
What Factors Can Cause A Decrease In Testosterone?
Age. Pretty much all of the sex hormones decrease as we get older, and testosterone is no exception. However, this doesn’t mean that all older adults needs to take bioidentical testosterone.
Stress. There’s something called the “pregnenolone steal”, which is also known as the “cortisol steal”. When someone is in a stressed out state, the body will prioritize cortisol production at the expense of the sex hormones. An enzyme called 17,20 lyase will become inhibited, and this will lead to decreased production of DHEA and androstenedione, which in turn will lead to decreased testosterone levels. This is one of the main reasons why many men and women have low testosterone levels, and I discussed this in greater detail in a blog post entitled “The Negative Impact of The Pregnenolone Steal“.
Nutrient deficiencies. The literature shows that having certain nutrient deficiencies can affect testosterone levels. For example, there is evidence that zinc can play a role in modulating serum testosterone (16) (17). Some studies show that vitamin D supplementation may increase testosterone levels (18) (19), although other studies suggest that this isn’t the case (20) (21).
Poor sleep. There does seem to be a relationship between low testosterone levels and less sleep (22) (23). However, while it is possible that not getting sufficient sleep can lead to low testosterone levels, it’s also possible that low testosterone levels can in turn decrease sleep quality.
Environmental toxins. There is evidence that certain environmental toxins can cause decreased levels of testosterone. Mercury can affect the testosterone levels (24), and there is also evidence that bisphenol A (BPA) can lead to a decrease in the testosterone levels (25) (26).
Excess aromatase activity. Remember that aromatase is an enzyme that converts testosterone to estradiol, and so if someone has increased aromatase activity then this can lead to decreased testosterone levels and increased estradiol levels.
What Factors Can Cause Elevated Testosterone?
PCOS. I briefly mentioned earlier how PCOS is usually characterized by high free testosterone levels. For more information I would refer to the article I wrote on PCOS.
Taking bioidentical DHEA or testosterone. Not surprisingly, taking too much bioidentical testosterone can cause elevated testosterone levels. However, since DHEA is a precursor of testosterone, taking high doses of DHEA can also cause elevated testosterone levels.
Cross contamination. If you aren’t taking testosterone, but someone in your household is using a testosterone cream, then it is possible to get exposed to the cream and have elevated testosterone levels. This is more common than you may think. So for example, if someone rubs testosterone on their body and doesn’t wash their hands thoroughly, and then they touch the door knob that is touched by other people in the house, then those people will be exposed to testosterone. Of course this applies to other hormone creams as well. In fact, I came across a study which looked to determine if there was absorption of vaginal estrogen cream by men during sexual intercourse, and the study showed that this is in fact true, while reducing estradiol absorption in women (29).
Speaking of creams, apparently some over the counter body creams and lotions include small amounts of testosterone, even though it’s not on the label. I’m not suggesting that this is common, but if someone has elevated testosterone levels and they aren’t taking bioidentical testosterone, and if cross contamination isn’t the reason, then this is something to consider. This is yet another reason to try using products that are certified organic.
What Role Does Testosterone Play In Thyroid Health?
Free testosterone is reduced with primary hypothyroidism, and thyroid hormone replacement normalizes testosterone (30) (31). On the other hand, one of these same studies showed that those with hyperthyroidism frequently will have elevated levels of testosterone (30). This doesn’t make much sense to me, as sex hormone binding globulin (SHBG) is usually elevated in those with hyperthyroidism, and high SHBG is associated with a decrease of free testosterone. In addition, hyperthyroid men may have abnormalities in their hypothalamic-pituitary-testicular axes (32).
Testosterone can also play a role in autoimmune conditions such as Graves’ Disease and Hashimoto’s Thyroiditis. One study showed how testosterone might prevent Th1 differentiation (33). I’ve spoke about the Th1 and Th2 pathways in other articles and blog posts, and I have mentioned how in most cases Hashimoto’s Thyroiditis is considered to be a Th1 dominant condition. And so by preventing Th1 differentiation, testosterone might help to prevent this condition from developing. The same study showed that androgens such as testosterone can inhibit Th17 differentiation (33). Th17 cells are increased in autoimmune conditions. Keep in mind that this was a single in vitro study, and so more research is needed in this area. However, another study showed that testosterone can increase regulatory T cells (34), which play a role in suppressing autoimmunity.
Does this mean that men and women should consider taking testosterone? Well, I do think that if someone has a testosterone deficiency it should be corrected, and this in turn might prevent someone from developing an autoimmune condition, or benefit someone with an existing autoimmune condition. However, it makes sense to try to address the cause of the hormone deficiency, rather than rely on taking testosterone for a prolonged period of time.
Testing for Testosterone
Testosterone can be measured through the blood and the saliva. Total testosterone measures testosterone that is mostly bound to a protein, while free testosterone means that it is free in the circulation. Approximately 98% of testosterone is bound to a protein (either SHBG or albumin), whereas only 25 of testosterone is in the free form. In saliva you are always measuring the free form of the hormone. And the research does show that saliva is a reliable method of testing for testosterone (35).
The reference range for total testosterone in the blood is 300 to 1,100 ng/dL. You ideally want to test for this early in the morning, and if testosterone is low it is a good idea to repeat the test. The lab reference range for free testosterone is 6.6 to 18.1 pg/mL. Whenever testing for testosterone it also is a good idea to test for LH, FSH, and SHBG.
How To Increase Testosterone Levels
Improve adrenal health. Remember that if someone deals with chronic stress the body will focus on producing cortisol, and this in turn will result in a decrease in androgens, including testosterone. As a result, doing things to improve the health of your adrenals is essential to having healthy testosterone levels. In addition to doing everything you can to try to reduce the stress levels, you also want to improve your perception of handling stress. Incorporating mind body medicine techniques such as meditation and yoga can help greatly. And of course eating well is also important.
Exercise and resistance training. Doing some moderate high intensity interval exercise a few times per week, along with some resistance training can help to increase testosterone levels.
Increase protein intake. As I mentioned earlier, eating a low protein diet can cause a decrease in testosterone, and so you want to make sure you are consuming enough protein.
Supplement with zinc and vitamin D. Since a deficiency of zinc or vitamin D can cause a testosterone deficiency it makes sense to make sure you have adequate levels of these nutrients. It’s easy to test for vitamin D through the blood to see if you are deficient. It’s not as easy to test for zinc, but you can always experiment with taking a zinc supplement for a couple of months and see if this helps to raise the testosterone levels. You just want to be careful not to take large doses of zinc for a prolonged period of time, as this can cause a decrease in copper.
Tribulus. This is an herb, and there is evidence that tribulus can increase testosterone levels when combined with other pharmacological components (36) (37). On the other hand, when taken by itself it doesn’t seem to increase testosterone levels in humans.
Use natural aromatase inhibitors. For those with excessive aromatase activity, taking natural aromatase inhibitors can help. Some of the agents which can inhibit aromatase activity include resveratrol, pumpkin seed extract, white button mushrooms, and stinging nettles (40) (41) (42).
In summary, testosterone is a sex hormone that has many important functions. Testosterone can convert into estradiol or dihidrotestosterone (DHT). As a result, high levels of testosterone can overconvert into estradiol, leading to estrogen dominance. Testosterone plays a role in increasing muscle mass, improving cognition, increasing bone density, improves insulin sensitivity, and can help prevent cardiovascular disease. Some of the signs and symptoms of a testosterone deficiency include decreased libido, vasomotor instability, decreased bone mineral density, depression, fatigue, erectile dysfunction, and reduced muscle strength/mass. Some of the ways to increase testosterone levels include improving adrenal health, resistance training, consuming enough protein, supplementing with zinc and vitamin D, taking natural aromatase inhibitors, and tribulus and cordyceps can also help to increase testosterone production in some cases.