While the root cause of androgenic alopecia, or male pattern baldness, is the same for almost all men, the timing, pace and extent of hair loss varies greatly because of three important factors: genes, hormones and age.

The Genetics of Hair Loss

Stop thanking your mother for you hair loss woes. Research shows that male pattern baldness is a polygenetic trait that can involve more than one gene and can be inherited from your mother, your father, or both parents.

Genes are the working subunits of your hereditary or DNA. Each gene contains a particular set of instructions, usually coding for a particular protein or for a particular function. Genes are found in every cell of our bodies and control everything from our eye color, to our height, to our ability to even curl our tongues. For most, they also control hair loss.

Every human’s genome, or total compliment of 20,000 plus genes, is stored in 23 different pairs of chromosomes. All but one of the 23 pairs of chromosomes are called “autosomes,” or non-sex chromosomes. The remaining pair holds the sex chromosomes, also known as the X or Y chromosomes. When this pair contains one X and one Y chromosome, the person is genetically male. If this last pair contains a set of two X chromosomes, the person is genetically female. It is strongly believed that the gene responsible for hair loss is found only in X chromosomes.

Genes are either dominant or recessive. Dominant genes show their effect even if the individual only has one copy present in one chromosome. Androgenetic alopecia is a felt to be a “dominant” genetic trait that is passed down by your mother or father, but with a slight predisposition to the maternal side. For a recessive gene to show an effect, there must be copies in each chromosome of a pair.

Even though androgenetic alopecia originates from a dominant gene, it still must be turned on, or “expressed,” for male pattern baldness manifest. Factors that can turn this gene on, alone or in concert, can be hormones and age, and sometimes even stress or a medical condition.

The human genome was sequenced more than a decade ago, but little is currently understood on what each of these individual genes do and how they affect the cycle of hair growth. Gene therapies to treat male pattern baldness have been tried with some success, but these research efforts are still very much in their infancy.