In general, those who begin losing hair in the second decade are those in whom the hair loss will be the most severe. In some men, initial male-pattern hair loss may be delayed until the late third to fourth decade. It is generally recognized that men in their 20's have a 20 percent incidence of MPHL, in their 30's a 30 percent incidence of MPHL, in their 40's a 40 percent incidence of MPLH, etc. The amount of androgens present does not need to be greater than normal for MPHL to occur. If androgens are present in normal amounts and the gene for hair loss is present, male pattern hair loss will occur.
Receptors exist on cells that bind androgens.
These receptors have the greatest affinity for DHT followed by testosterone, estrogen, and progesterone. After binding to the receptor, DHT goes into the cell and interacts with the nucleus of the cell altering the production of protein by the DNA in the nucleus of the cell. Ultimately growth of the hair follicle ceases. The lighter color, miniaturized hairs cause the area to first appear thin. Involved areas in men can completely lose all follicles over time.