The hair growth cycle consists of three phases: anagen (active growth lasting 2-7 years), catagen (transition), and telogen (resting/shedding). Healthy adults shed 50-100 hairs daily as part of normal cycling. When the anagen phase shortens or more follicles enter telogen prematurely, net hair density declines—a process that can reduce visible hair volume by 50% before most people notice thinning.
In androgenetic alopecia—the most common form—the enzyme 5-alpha reductase converts testosterone into dihydrotestosterone (DHT), which binds to susceptible follicles and progressively shrinks them. Each successive growth cycle produces thinner, shorter, and lighter hairs until the follicle can no longer produce visible hair.
Nutritional deficiencies compound hormonal effects significantly. Iron, ferritin, zinc, biotin, and vitamin D are all essential cofactors in the keratin synthesis pathway. Studies show that up to 72% of women with hair loss have concurrent nutritional deficiencies that impair the follicle's ability to produce strong, healthy hair shafts.
