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Question from practice: Greying hair — is there a solution?

JelenaGoriats/dreamstime.comA. Loss of hair colour (canities) is an age-related phenomenon. The mechanisms of hair pigmentation are complex and not yet fully understood.

Spontaneous repigmentation of hair has been reported in medical literature (eg, after radiation therapy and after inflammatory events such as erythrodermic eczema), but it is not common.

At present there is no medicine or food supplement that is known to restore the colour in greying or white hair. And there is no evidence for the effectiveness of folk remedies such as rubbing the scalp with butter. Reversal of colour loss, however, is being researched and it is possible that, in future, a pharmacological treatment might be available. The agents that have been suggested as possible candidates for pharmacological reversal of canities include catalase and the TRP-2 enzyme.

How hair is coloured

Melanocytes in the bulb of the hair follicle are responsible for the production of melanin. This is transferred to the hair shaft as it grows, a phase of hair development (anagen) that typically lasts about three years in humans. The activity of the melanocytes is closely coupled with the growth phase of the hair — during the catagen (cessation) and telogen (rest) phases melanogenesis stops. This is different from the behaviour of epidermal melanocytes, which produce melanin continuously. Different hair colours are produced by different forms of melanin and this is under genetic control.

Melanin is produced from L-phenylalanine or L-tyrosine, and tyrosinase is essential for two of the early steps. Hair colour is linked to tyrosinase activity and so the regulation of this is critical. A number of other substances are known to regulate hair pigmentation, including hormones, neurotransmitters, cytokines, growth factors, eicosanoids, cyclic nucleotides, nutrients and the micro-elements.

There is a reduction in the numbers of melanocytes with age and this occurs more rapidly and sharply with hair follicle melanocytes than with epidermal melanocytes, suggesting separate control mechanisms or regulation by different melanogenetic clocks. Although the exact mechanisms are still unknown, heredity plays an important role: if your parents went grey early there is a strong possibility that you will too. The average age of onset of hair colour loss for Caucasians is mid-30s, for Asians late-30s, and for Africans mid-40s.

Supplements and research

Oxidative stress as a result of the formation of reactive oxygen species during melanin synthesis is believed to play a part in the ageing of melanocytes and, therefore, the greying of hair. Hydrogen peroxide is known to accumulate in greying hair and this is believed to be linked to a decrease in the catalase enzyme activity. This has provided the rationale for a catalase supplement that is sold in the US to reverse greying of hair, although I have been unable to find any evidence for its effectiveness. It seems doubtful that oral administration of a peptide enzyme could be efficacious.

Another feature of ageing human melanocytes is the loss of tyrosinase-related protein 2 (TRP-2), a melanogenic enzyme. Researchers at L’Oréal believe that oral treatment with TRP-2 might be able to prevent colour loss but this means it would have to be taken before hair begins to turn grey — something that is hard to predict. However, there is some concern that such treatment might interfere with the diagnosis of melanoma because TRP-2 is also expressed in melanomas.

Another mechanism that has been hailed by the popular press as a potential target for the prevention of grey hair is the Wnt-signalling pathway. This stemmed from a publication that showed that this pathway is involved in co-ordinating the activity of epithelial stem cells and melanocyte stem cells in hair follicles.1 The Wnt network is also involved in embryogenesis and cancer development, and since we are still improving our understanding of this its manipulation to control hair colour is probably a long way off.

At present there is no proven systemic treatment to prevent or reverse loss of hair colour and so the only reliable option is to dye the hair. As our understanding of the mechanisms deepens, new approaches could be developed.

Key points

  • At present there is no medicine or food supplement that is proven to restore the colour in greying or white hair although available supplements marketed to reverse colour loss include catalase.
  • Mechanisms such as the loss of TRP-2 and the Wnt-signalling pathway have been researched as potential targets for preventing grey hair but these mechanisms may also have a role in cancer development.

 

About the author

Christine Clark, PhD, FRPharmS, is a freelance pharmaceutical writer

Citation: The Pharmaceutical Journal URI: 11110100

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