Danielle Little, of Westland High School, asks :-

Why do some people go bald?

Eric Espiner, a Endocrinoligist with Canterbury Health, responded.

Scalp hair thinning in most humans is a natural process which when severe, results in balding.

The process begins after puberty, affects both sexes (males more severely) and is inheritable. It is not known exactly what determines scalp hair thinning in the first place but sex hormones are important factors. `Male pattern' balding does not occur in men who lack the sex steroid testosterone - unless testosterone treatment is given in which case balding may occur as in normal men.

Similarly women who make excessive amounts of testosterone may show a male pattern of receding hairline. Recent research shows that the cells nourishing the scalp hair root contain an enzyme which can convert testosterone to an even more active form of the hormone, di hydro testosterone. If there is a high level of gene expression, more of the di hydro testosterone will be formed in the hair root - leading to greater hair loss in those carrying the defective gene.

By applying to the scalp a chemical which inhibits the enzyme it may eventually prove to be possible for the sorely afflicted to keep their hair on.