Androgentic alopecia is the culprit behind male and female pattern hair loss. Sometimes, the problem is just in your genes.
Worse, it can skip generations, which means you can suffer from baldness even if your father or grandfather don't.
Male pattern baldness is closely related to testosterone. Testosterone has many functions in the body, including the regulation of hair growth. When you have male pattern baldness, your hair is susceptible to absorbing significant amounts of dihydrotestostrone (DHT) which disrupts the dermal papilla's signalling abilities.
DHT also causes imbalances in calcification regulators, causing damaging inflammation, tissue fibrosis, excessive calcification, and the loss of blood flow. The result? A damaged hair growth cycle that can't repair itself. Eventually hair follicles stop receiving both nutrients and oxygen, and die.
In some extreme cases you'll see excess calcification and fibrosis. The tissue hardens and creates a claustrophobic environment for the hair follicles. The effect is a bit like having weeds in a garden: allow them to grow uncontrollably, and all the surrounding plants die off. The reasons are the same: the weeds are eating up all the nutrients, and there aren't enough for all the plants to survive. Thus, they begin to die off.