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androgenetic alopecia


  • 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:

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)
  • other candidate genes include3):
    • SRDA1 and SRDA5 coding for the two variants of the 5a-reductase enzymes
    • insulin gene
    • the aromatase gene
    • gene for the Erα oestrogen receptor
    • the non-recombinant area of the Y chromosome
    • IGF-2 gene
      • a polymorphism of this confers a high risk of polycystic ovary syndrome (PCOS) which may be related
      • while this gene is autosomal, the maternal allele is de-activated due to genomic imprinting


  • oral inhibitors of 5α-reductase arrest progression of androgenetic alopecia in over 90% of men and partially reverse it in over 65%
alopecia_androgenetic.txt · Last modified: 2019/07/14 02:46 (external edit)