The process of greying of hair also called canities is a normal physiological phenomenon, which starts with increase in age.
The term premature greying is used if the greying of hair has started before the age of 30 in Africans, 20 in Caucasians and 25 in Asians.
Before going into the topic of greying one must understand something about the pigment or the color of hair
The hair color is based on the production of melanin pigment and its distribution along the keratinocytes. Towards the end of the anagen phase of hair growth cycle melanin synthesis gradually stops after a reduction in amount of melanin synthesizing enzymes like tyrosinase. The process of pigment again starts during early anagen phase.
Commonly greying of hair starts in the sideburns and the temple region.
In majority of cases the premature greying is not pathological but in some it has been found to be associated with
- Hereditary: This may be inherited as an autosomal dominant trait.
- Autoimmune diseases like thyroid disorder, Addison’s disease, Pernicious anemia
- Nutritional deficiencies: Recent studies have shown that decreased bone density and hence deficiency of vitamin D and calcium is related to the premature greying of hair in certain percentage of patients. Vitamin B12 and decreased iron also affects hair growth and pigmentation.
- Smoking: Smoking has shown some correlation with premature greying of hair.
- Prolong stress