I often receive accusations from colleagues who don’t understand the difference between total testosterone (inactive form + active forms of testosterone) and free testosterone (active form.) As several of these very educated and accomplished doctors claim, my female patients’ testosterone levels are the same as a male’s testosterone level. They base this analysis on various blood tests that my patients undergo. However, any analysis that considers testosterone levels to be equal between men and women is a misleading and misinformed analysis. Testosterone, in fact, functions very differently in women than it does in men. Women have testosterone throughout their productive lives, and it is 3X as plentiful as estradiol (young women’s estrogen). After the age of 40, however, testosterone drops to a level that is too low to produce the positive effects that it once produced, and many negative symptoms may develop, including:
- Belly fat increases
- Loss of Libido
- Loss of muscle mass, strength and stamina
- Memory loss
- Dry eyes
- Dry vagina
- Sagging skin
- Increase in subcutaneous fat
Loss of testosterone after the age of 40 can also cause many of the problems that Internal Medicine doctors regularly treat with individual medicines for each problem, including:
- High Cholesterol
- High Triglycerides
- Weight gain/fat gain
- Balance problems
- Sarcopenia (loss of muscle mass and strength)
- High blood pressure
- Diabetes, insulin resistance, hypoglycemia
- Heart disease/inflammation, weak heart muscles, atherosclerosis
- Alzheimer’s disease
Most of these problems can be prevented or treated by replacing the testosterone we had in youth. This method is the same for both women and for men. Replacing testosterone in male patients is common practice and widely accepted as a means of resolving the underlying issues of the symptoms above. Interestingly, women need testosterone for the very same reasons. The problem that non-gynecologist physicians and even some within my own specialty don’t understand (and may find upsetting) is that the necessary hormone replacement dose of testosterone in women after 40, relative to their total testosterone, is not the same as what it is for men. Consider the following:
Fact 1: Men have many more genetically-programmed, cell-based receptors than women have. So, the effects of testosterone in men is amplified. In other words, a lot less testosterone makes a bigger impact in men.
Fact 2: Women lose testosterone receptors throughout their body after the age of 40. Men don’t start losing those receptors until 15 years later. So, women feel the effects of low testosterone earlier and more acutely.
Fact 3: Men have a much higher percentage of the active form of testosterone than women have. If a woman and a man each have a level of 200 total testosterone, the woman may have only 10 pg/ml of free testosterone, and the man may have 100 pg/ml of free testosterone. The total number doesn’t mean much in women except for serving as a marker to determine the ideal level for that individual woman, as well as how efficiently replacement testosterone is absorbed in the blood stream.
Fact 4: Women have much more estrogen than men. Estrogen does two things to decrease the effectiveness of testosterone in women: 1) It competes better (3 to 1) with testosterone for the same receptor sites on every cell. More estrogen means a lesser effect from testosterone. Men have almost no estrogen, so their testosterone attaches to these receptors without competition and thus is much more effective. 2) Estrogen increases the production of the protein SHBG from the liver, which increases the amount of protein that deactivates testosterone. Men have very little estrogen, and therefore have a higher free testosterone level.
Fact 5: As women age the percentage of active testosterone begins to decrease. This begins at a younger age for women than it does for men, and continues throughout their lifetime.
As you can see, the activity of testosterone in women and men is completely different for the same total testosterone level. You cannot say to a woman, “You have the testosterone of a 40 year old male,” because the same total will have a fraction of the effect as it would on a man. There are fewer receptors on a woman’s cells and the receptors for testosterone have to compete with estradiol to attach to a cell. Women have fewer testosterone receptors to begin with. We lose testosterone as we age beyond 40. Therefore, we need hormone replacement in order to prevent illness and disability. Testosterone can take the place of multiple drugs, and women need a higher level of free testosterone than we did before the age of 40.