Amos Barshad writes in The New Yorker
In the nineteen-forties, a Brooklyn anatomist named James Hamilton studied prisoners in Oklahoma who, having been convicted of sexual assault, were castrated. Hamilton identified testosterone as the root of hair loss, and showed that men castrated before or during puberty did not go bald. He then injected groups of castrated adult men with testosterone and—duly, cruelly—watched their hair fall out.
In the following decades, researchers learned that testosterone does not work alone. An enzyme converts testosterone into a substance called dihydrotestosterone, or DHT, which causes hair follicles to shrink. DHT attacks the dermal papilla, the “brain” of the hair follicle, and is the main cause of male-pattern baldness, which affects more than fifty million men in the United States and also—largely unremarked upon, but true—more than thirty million women.
Barshad has a funny paragraph about Trump:
I’d come to think that the simplest answer was the right one: this was regular male-pattern baldness, elaborately covered up. But the Air Force One incident only deepened the mystery. What kind of hair afflicted by male-pattern baldness rises in the back? I suddenly had no idea which parts of his head contained which hairs. Watching the flaps on the back of his head shoot up again and again, I became unmoored in my beliefs.
When I was young and full of hair, I never thought that I would loose my hair. Now I am bald as fuck. Comparing to all the flaws on my appearance, being bald is not the worst. Other then shaving my head every two or three weeks, I wake up every morning and do nothing to my hair. I don’t even need to go a barbershop. I just don’t care about hair.