Chapter 90
Going Bald
Does hair dye cause cancer?
Because there is typically no way to reverse the loss of hair color, up to 60 percent of men and women in Western countries use hair dyes, often to cover gray hair. You can see the whole story at see.nf/dye, but overall you learn there that the hair-dye industry, in response to the warning labels demanded by the FDA in 1979, developed new formulations to exclude the most carcinogenic components of their products. That led to some cancers becoming less common, but not others, which is why some scientists concluded that one should “expose oneself to hair dyes as little as possible.”
Going Bald
Every person has about 100 000 hairs on their head and normally loses around 100 per day, because old hairs are replaced by new ones. But aging also includes hair becoming thinner, which affects at least 50 percent of women over 50 and 40 percent of men over 35; over a lifetime this prevalence rises to 80 percent. Age-related hair loss is referred to in the hormone and gynecology literature as androgenetic alopecia; in dermatology one speaks of male or female pattern hair loss. Either way, hair loss is chronic and progressive, especially on the top of the head.
Cause and consequences
The word “androgenetic” contains a clue to the cause of male hair loss. Androgens (from the Greek andro for “man”), the male hormones such as testosterone, impair hair follicles on the head. Quite ironic, because these very hormones are also the main reason for hair growth in other parts of the body, for example on the face or in the armpits. (Eyelash follicles are not influenced in either direction.) As far back as the time of Hippocrates, perhaps even earlier, people knew something about the role of male hormones, because Hippocrates noted: “Eunuchs … do not go bald,” which indeed seems to be true. Castration can also stop the progression of hair loss in men, but it cannot reverse it. The role of testosterone was recognized when a pathologist at Yale noticed that the castrated twin brother of a bald man had a full head of hair. In an experiment, he gave the castrated brother testosterone, after which he, too, went bald.
If you see something ethically problematic in this, you should ask yourself why this man was castrated in the first place. Castration was recommended for the “feebleminded” in order to “curb abnormal behavior,” such as the “unspeakable habit” of masturbating. If, in the 19th century, the original justification for removing testes and ovaries in “idiotic children” was partly based on the effort to keep those “known to masturbate” in check, the rationale in the cultivated 20th century shifted toward eugenics. Under the eugenics laws in the United States—the first in the world—people with intellectual disabilities were routinely sterilized without their consent and without their knowledge, a practice that the U. S. Supreme Court upheld in 1927. In the 1930s, a loud proponent of this approach complained: “The Germans are beating us on our own turf.”
Does being bald bring any evolutionary advantages? Even though bald men are exposed to more sunlight, they do not have better values for the “sunshine vitamin” D. Maybe they are more virile because they have more testosterone in their blood? On the contrary, researchers found that bald men are sexually less attractive and, on average, have fewer sexual partners overall. What they get from higher testosterone levels is a greater risk of prostate problems. While men with the genetic predisposition for a lifelong higher testosterone level seem overall to have better bone density and less body fat, they are more likely to suffer not only from hair loss but also from prostate cancer and high blood pressure.
The connection to high blood pressure may explain why MRI scans more often detect traces of small strokes (white matter hyperintensities) in the brains of men with hair loss. The majority of studies on this topic found that baldness is a risk factor for cardiovascular disease. Researchers proposed that physicians should take baldness as a visible sign to identify men at increased risk of heart disease and initiate preventive interventions. In women, hair loss points to a ninefold higher risk of metabolic syndrome, a cluster of risk factors that includes extra body fat around the waist, elevated blood sugar, elevated blood pressure, and high triglyceride levels.
Reversible hair loss
What role male hormones play in women’s hair loss is still unclear, because only very few women with female pattern hair loss have elevated androgen levels in the blood. In women, hair tends to become thinner rather than progressing to baldness, especially on the top of the head and in the front, and unlike men they may feel less called to shave their heads. Female pattern hair loss can have many causes.
When a man loses his hair, that is considered normal, but in women it should be evaluated. For example, one third of women with hypothyroidism, a disease that affects women up to seven times more often than men, have diffuse hair loss. That is usually irreversible despite hormone replacement, which shows how important early diagnosis is. A common form of hair loss is called telogen effluvium and can be triggered by oral contraceptives, crash diets, and giving birth.
Unlike the hair follicles on our bodies and in our pets, which are in an unchanging “telogen” resting phase, about 90 percent of hair follicles on our scalp are in an “anagen” phase of active growth. In both men and women, stressful events such as surgery or illness may trigger a mass restart of the hair cycle, shifting follicles into the telogen phase, but that lasts only about two to three months before the cycle begins anew.(Covid-19 was one of the main triggers for this.) This restart can mean that, a few months after the traumatic event, hair suddenly falls out in clumps, because all the new hairs push out the existing hair at the same time rather than gradually. Most people do not connect this with the upheaval they went through and fear they are going to go bald, but telogen effluvium is limited. The hair loss stops as the new hairs grow in over the following months, but it can take a year or longer until you are as good-looking as you were before.
How do you know what kind of hair loss you have? You can distinguish normal hair loss from telogen effluvium with the pull test. Do not wash your hair for at least 24 hours, then take about 50 hairs between your thumb, index finger, and middle finger and pull them gently and slowly away from the scalp. Normally most hairs are in an active growth phase, so less than 10 percent should come out. If more come out and you see a small white bulb at the lower end, then you may have telogen effluvium.
Modifiable risk factors
Bald men not only have higher testosterone levels but also more testosterone receptors in the scalp, mostly genetically determined. In identical twins there is an 80 to 90 percent concordance, so if one loses his hair, in eight or nine out of ten cases the other will also go bald. But what about the remaining 10 to 20 percent who have the same genes but different degrees of hair loss? What can we learn from them?