The degree of thinning that an individualexperiences can vary due to bothexternal factors, such as stress,exposure to free radicals & UV rays,& internal factors, such as geneticsand follicle sensitivity to the hormoneDihydrotestosterone, or D.H.T.
Androgenetic Alopecia, or "pattern baldness", occurs in both men & women whose hair follicles are sensitive to D.H.T. (a primary cause of thinning hair & hair loss).
Typically, hair on the top & front of the head is most sensitive to D.H.T. Over time, this hair will become weaker, finer, & may eventually stop growing.