androgenetic alopecia is male pattern balding which appears to have a multi-factorial causation although genetic polymorphisms appear to have a key role which may influence the hair follicle cycle and the drivers of this cycle such as androgens, and insulin-like growth factors (IGFs)
30% of men developed androgenetic alopecia by the age of 30 and 50% by the age of 50
the three key features of androgenetic alopecia pathogenesis are:
alteration of hair cycle dynamics
follicular miniaturisation
inflammation
eunuchs, patients with androgen-insensitivity syndrome and those with 5α-reductase deficiency do NOT go bald in this manner, suggests that androgenetic alopecia is induced by activation of follicular androgen receptors by dihydrotestosterone.
there are possible associations with other conditions such as:
prostate cancer - 50% increased risk with vertex pattern, but no increase risk with frontal pattern, although all forms showed an increased risk of high grade cancers in men aged 60-69yrs 1)
Genetic factors
this form of alopecia clearly has a familial association and is more common in some ethnic groups
the androgen receptor gene Stu1 restriction fragment length polymorphism on the X chromosome appears to be necessary (as it is present in 98% of young bald men and 92% of older bald men) but of itself is not sufficient to cause the condition (it occurs in 77% of non-bald men)2)