What kills hair follicles naturally?

Could you elaborate on the natural factors that contribute to hair follicle demise? I'm particularly interested in understanding the biological processes and environmental triggers that may lead to hair loss. Are there specific hormones, nutritional deficiencies, or age-related changes that play a role? Also, are there any lifestyle habits or external factors that can accelerate this process? I'm seeking a comprehensive overview of the natural causes of hair follicle deterioration.