Androgenetic alopecia is characterized by a loss of hair from the scalp that follows a defined pattern (Hamilton, 1951). It occurs in women as well as in men. It is caused by a shortening of the anagen (growth) ... Androgenetic alopecia is characterized by a loss of hair from the scalp that follows a defined pattern (Hamilton, 1951). It occurs in women as well as in men. It is caused by a shortening of the anagen (growth) phase and miniaturization of the hair follicle, which results in the formation of progressively thinner, shorter hair (Bergfeld, 1995). In men, the condition is often referred to as male pattern baldness (MPB) and appears to be androgen-dependent (Hamilton, 1942). The condition is hereditary, and follows a pattern that may be consistent with an autosomal dominant trait (Osborn, 1916). Linkage evidence for an autosomal locus on 3q26 (AGA1) has been identified (Hillmer et al., 2008). See 300710 (AGA2) for a discussion of X linkage of androgenetic alopecia. A third locus has been found on chromosome 20p11 (AGA3; 612421).
Hamilton (1951) classified pattern baldness and gave incidence figures.
Carey et al. (1993) identified families with polycystic ovaries (PCO; 184700) in females and premature male pattern baldness in males, inherited in an autosomal dominant pattern. The ... Hamilton (1951) classified pattern baldness and gave incidence figures. Carey et al. (1993) identified families with polycystic ovaries (PCO; 184700) in females and premature male pattern baldness in males, inherited in an autosomal dominant pattern. The authors postulated that polycystic ovary syndrome may be the female phenotype of premature male pattern baldness.
In studies of 81 affected individuals from 14 Caucasian families in which females had polycystic ovaries and males pattern baldness, Carey et al. (1994) found a single-base change in the 5-prime promoter region of the CYP17 gene (609300), ... In studies of 81 affected individuals from 14 Caucasian families in which females had polycystic ovaries and males pattern baldness, Carey et al. (1994) found a single-base change in the 5-prime promoter region of the CYP17 gene (609300), which seemed to modify the expression of the syndrome in some families but could be excluded as the primary genetic defect. Ellis et al. (1998) found no evidence that the gene for either of the 2 isoforms of the steroid 5-alpha-reductase enzyme (SRD5A1, 184753; SRD5A2, 607306) is involved in the genetics of MPB. From a population survey of 828 healthy families, they identified 58 young bald men (aged 18 to 30 years) and 114 older nonbald men (aged 50 to 70 years) for a case-control comparison. No significant differences were found between cases and controls in allele, genotype, or haplotype frequencies for restriction fragment length polymorphisms of either gene. Furthermore, no clear inheritance pattern of male pattern baldness was observed. A relatively strong concordance for baldness between fathers and sons found in this study was considered inconsistent with simple mendelian autosomal dominant inheritance, since bald sons would be expected to inherit the condition from either the mother or the father in equal proportions. As many as 44 bald sons (i.e., 81.5%) had bald fathers. Sprecher et al. (2000) assessed the pattern of androgenetic alopecia in 31 healthy male second-degree relatives of patients affected with atrichia with papular lesions (209500) belonging to a large consanguineous kindred. No difference in age at onset or extent of androgenetic alopecia was observed between healthy homozygotes and heterozygous carriers of the mutation in the 'hairless' gene (HR; 602302). Sprecher et al. (2000) concluded that the presence of a deleterious mutation in one allele of the HR gene does not affect the pattern of androgenetic hair loss. To further test the hypothesis that the HR gene may be involved in androgenetic alopecia, Hillmer et al. (2002) systematically screened HR for genetic variability by SSCA in 46 unrelated men with androgenetic alopecia. To test for involvement of HR in the development of androgenetic alopecia, 7 common variants were genotyped in 61 families with 93 affected offspring. The results were analyzed with the transmission/disequilibrium test (TDT). SSCA showed 15 single-nucleotide substitutions: 8 missense mutations, 4 silent mutations, and 3 mutations in exon-flanking intronic sequences. TDT results showed a marginally significant association between androgenetic alopecia and variants 3379-29G/T (P = 0.024) and 2611-68C/T (P = 0.047). These results, however, did not remain significant after applying the conservative Bonferroni correction for multiple testing. Hillmer et al. (2002) concluded that these results did not provide evidence for a strong involvement of HR in the development of androgenetic alopecia, although a minor role could not be fully excluded.