Men and women normally produce testosterone.
The normal functions of testosterone in men include sex drive or libido, sperm production, increased muscle mass, increased energy and vitality, as well as human behavior aspects of aggression and being competetive. In men, a low testosterone level leads to unwanted side effects that can severely hamper quality of life due to loss of libido, fewer spontaneous erections, impotence (erectile dysfunction) and infertility. Other complications permeate the transition to cause a loss of confidence, lack of motivation, sleep loss, increased body fat, loss of muscle mass, and even decreased bone density.
The normal function of testosterone in women include the same characteristics of increased muscle mass, increased energy and vitality. During menopause, the increased estrogen leads to a relative decrease in testosterone that can lead to loss of libido, infertility, and decreased bone density.
In the search to correct a low testosterone level, a frequently asked question is:
What’s a normal testosterone level?
Well… it’s a little complicated…
Many consider it a mistake to “just” order testosterone levels. That is because the endocrine glands also keep many other hormone levels normal. Plus, the brain’s pituitary gland stimulates various organs to make their hormone on a negative feedback loop. Finally, add the fact that the number three cause of death in the US is medical error, and it shows that mistakes can be made in either over- or under-diagnosing hormone levels as being either too high or too low, as well as missing a dual diagosis.
The Three Forms of Testosterone
Two forms of testosterone are “bound” to protein, taking them out of action, so to speak, and making them not bioavailable. The third form is “free” and this is the one that has an effect:
1. Bound with sex hormone binding globulin (SHBG): makes up 65% of testosterone.
2. Bound with the protein albumin: makes up about 35% of testosterone, and can be “unbound” when needed.
3. Free: makes up 2% of testosterone, and is bioavailable in the bloodstream to act on organs like the brain, penis, and muscles.
While testosterone levels decrease with age in men, there is a complimentary increase in sex hormone binding globulin (SHBG) such that SHBG gradually binds more testosterone molecules,effectively taking them out of the blood stream level. This means that with age, free, bioavailable testosterone decreases more abruptly than total testosterone levels. That leaves less testosterone circulating in the system, even if production remains normal. A man’s total testosterone level may be normal but his free testosterone may be abnormally low, rendering him hypogonadal.
Additionally, different labs have different low and high values for testosterone levels, with some fluctuation. Furthermore, one must note the numerical values and their units, as the two ways to measure blood concentrations of testosterone are ng/dL and pg/mL. And there is also a difference between normal and optimal levels.
Ranges of testosterone blood values in men:
“Normal“: Total Testosterone: 250 – 1,150 ng/dL | Free Testosterone: 25 – 150 pg/mL
“Optimal“: Total Testosterone: 900 – 1,150 ng/dL | Free Testosterone: 150 – 200 pg/mL
Ranges of testosterone blood values in women:
University of Rochester Medical Center: 15 – 70 ng/dL
Blood test results are always evaluated in light of the clinical picture. “Optimal” testosterone levels differ significantly from “normal” levels, being in the top 10 – 15% range for clinical effect. Testosterone replacement should have the goal of avoiding superphysiologic levels that lead to undesireable side effects.
A full work-up of all systems is best provided by physician professionals who are board-certified and specialize in optimizing all hormone levels and organ systems, as well as comprehensively treating at the whole person within the parameters of their individual lifestyle and modifications.
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