While bodybuilding and athletes may come to mind with the word testosterone, it is actually an important hormone for both men and women. In men, low serum testosterone levels are linked to an increased risk of metabolic syndrome, type-2 diabetes, atherosclerosis, and heart disease mortality.[ref][ref] And in women, increasing testosterone levels are a risk factor for fatty liver disease.[ref] Higher testosterone levels in women with PCOS are also associated with insulin resistance and higher fasting glucose levels.[ref]
While age, diet, and lifestyle choices play a role in testosterone levels, there is also a fairly strong genetic factor at play.
The sex hormone-binding globulin (SHBG) binds to testosterone (and other sex hormones) in the bloodstream, making it biologically inactive and unable to enter the cells. Often SHGB levels are tested along with total testosterone levels to determine what part of the total testosterone is ‘free’ and available to be used by the cells.
Check your 23 and Me results for rs12150660 (v4 only)
- G/G: Lower average free testosterone
- G/T: lower average free testosterone levels
- T/T: normal testosterone levels
Check your 23 and Me results for rs6258 (v4, v5):
- T/T: lower free testosterone, decreased SHBG binding affinity for testosterone
- C/T: lower free testosterone, decreased SHBG binding affinity for testosterone
- C/C: normal testosterone
A large-scale study of 14,000+ men found that these SHBG variants were associated with testosterone levels. The more minor alleles that the men carried, the likelier they were to have low testosterone levels (<300ng/dl in this study). [ref]
Check your 23 and Me results for rs6259 (v5 only)
Check your 23 and Me results for rs1799941(v4, v5):
- A/A: higher SHBG levels, higher total testosterone levels[ref]
- A/G: somewhat higher SHBG levels, testosterone
- G/G: normal SHBG
Note that the FAM9B gene is on the X-chromosome, so males will only have one copy. Yes, guys, you can blame your mom for this one.
Check your 23 and Me results for rs5934505 (v4 only):
- T- allele: lower average serum and free testosterone levels [ref]
- C-allele: normal testosterone
The FSHB gene codes for FSH (follicle-stimulating hormone) beta-subunit. This is a hormone expressed by the pituitary gland and regulates the function of either the ovaries or testes.
Check your 23 and Me results for rs10835638 (v4, v5):
- T/T: risk of low follicle-stimulating hormone levels, reduced free testosterone [ref], increased risk of male infertility[ref]
- G/T: intermediate risk of low follicle stimulating hormone levels
- G/G: normal FSH
There are other gene variants that aren’t available via 23andMe (or similar) testing. Specifically, there is a commonly repeated section of the androgen receptor that plays a role in testosterone levels.
Best way to know if your testosterone levels are normal? Go get a blood test done to see what your levels actually are. Your doctor should be able to run the test, or you can order your blood test online (in the US) through a place like walkinlab.com. You can also now order a testosterone hormone test kit off Amazon (there are other brands available there also, so read through the reviews). Keep in mind with testing that testosterone levels can fluctuate over the course of the day, with the highest levels in the morning.[ref]
I’m actually not going to list a bunch of ‘lifehacks’ for increasing testosterone levels. I’m not an expert on the topic and wouldn’t want to steer anyone in the wrong direction here :-) You can all go to the bodybuilding forums (or reddit) for that type of information.
Environmental exposure to BPA and phthalates has been shown to be associated with increased SHBG levels and decreased testosterone (total and free) in children and teens.[ref] Another study looked at phthalate levels in a larger group and found that increasing phthalate levels were associated with decreased testosterone levels for boys and for men and women ages 40-60. [ref]