So you decided to get your testosterone checked and went ahead with a full male hormone panel – total testosterone, free testosterone, sex hormone binding globulin, and estradiol (sensitive). Your results have arrived, and you’re bewildered by the nonsensical tables, charts, and reference range bar graphs. Let’s break it down.
I describe all measures in nanograms per deciliter (ng/dL) unless otherwise indicated, because it’s by far the most common unit used in hormone panels. If you need help converting units, feel free to contact me.
Total testosterone is a measure of both free plus protein-bound testosterone concentrations in the blood. Because it’s nonspecific, it’s useful as a general gauge of androgenic hormonal health. If TT is low, lifestyle and diet factors can vastly improve this and all other measures in a more specific panel; if TT is very low, it may indicate hypogonadism or other HPT axis conditions best diagnosed by a doctor. Due to the complex interplay of testosterone, SHBG, luteinizing hormone, follicle-stimulating hormone, and estrogen, total testosterone readings can sometimes present falsely low, which is why I always order a full panel.
For a relatively healthy, fit man in his 20s or 30s, ideal results for total testosterone are between 700 and 1000 ng/dL. Between 40 and 50 years old, ideal results are between 600 and 900. The ranges continue to decrease by roughly 100 ng/dL per 10 years of age.
While total testosterone is a useful number, it only gets us halfway there. To get a fuller picture, we need to look at free testosterone and sex hormone binding globulin (SHBG). If you bought a full male hormone panel, these should be included.
Free testosterone indicates what portion of total testosterone is unbound in the bloodstream, ready to be mobilized. Triggered by other hormonal events in the HPT axis, free testosterone either binds to a T receptor site and begins a chain reaction leading to some kind of anabolic or androgenic response – muscle growth, bone density activity, body hair or beard follicle stimulation, etc – or encounters the body’s T-scavenging hormone (SHBG) and removed from active circulation based on signals from the adrenals or brain. Both events effectively lower the amount of free testosterone. Albeit not a perfectly accurate depiction, this essentially describes the process in which homeostasis of testosterone is achieved in the male body. There is another important event called aromatization, whereby T is synthesized into estrogen, which I’ll go into greater detail below.
Ideal results for a fit man in his 20s are between 10 and 25 ng/dL. The lower bound continues to decline to about 4 ng/dL until the age of 55, and the upper bound decreases by about 1 ng/dL per 5 years of age.
Sex hormone binding globulin (SHBG)
As I described in the last section, SHBG is a protein synthesized in the liver that binds to free testosterone (along with DHT and estrogen) in the bloodstream. All kinds of conditions can play a role in either low or high SHBG levels, including obesity, diabetes, hypo/hyperthyroidism, hepatitis, HIV, and even some medications. Unless total testosterone is abnormally low or SHBG levels are out of reference, I don’t worry too much about the exact numbers here.
Reference range for SHBG in a healthy adult male is between 20 and 60 nmol/L.
Estradiol is the mother hormone of estrogen. Precisely how much active estrogen the male body needs is hotly debated, but what is not debated is that it is in fact needed. Since men do not have ovaries (where the majority of estrogen is produced in women), the male body has another way of efficiently synthesizing the female sex hormone. When free testosterone in the blood encounters an enzyme called aromatase, the two bind together and a process aptly named aromatization begins. Aromatization converts testosterone into estradiol for later synthesis into estrogen and estrogen analogues, which contribute to sex drive and a variety of other functions in healthy men.
The difference between sensitive and typical estradiol measures is meaningful. While expert recommendations indicate the sensitive measure only provides more accurate results than typical at low levels of estradiol, anecdotes (albeit mostly from men on hormone replacement therapy) argue typical tests show far higher – and supposedly inaccurate – concentrations than the sensitive.
The importance of maintaining ideal concentrations of estradiol alongside the more conventionally male-associated hormones can not be overstated. Low levels of estradiol in men can lead to osteoporosis, low sex drive, and predisposition to bone fractures. High levels of estradiol can contribute to atherosclerosis, stroke, coronary artery disease, prostate enlargement, and even prostate cancer. The Life Extension Foundation summarizes mortality rates correlated with out-of-range estradiol levels:
A study published in the Journal of the American Medical Association (JAMA) measured blood estradiol (a dominant estrogen) in 501 men with chronic heart failure. Compared to men in the balanced estrogen quintile, men in the lowest estradiol quintile were 317% more likely to die during a 3-year follow-up, while men in the highest estradiol quintile were 133% more likely to die.
Ideal ranges for estradiol levels are between 21.8 and 30.0 pg/mL.
I’ll be writing more on all the hormones included in this post in the future. I think this is a good start in explaining how to interpret most lab results and promoting the value of a full panel instead of a singular measure advocated by most (typically total testosterone). Feel free to comment or hit me up with any questions.