medwireNews: Prepubertal girls with hypertrichosis are likely to have genetic variants of the androgen receptor known to be particularly sensitive to androgens, say researchers.
Their hormone levels, however, are largely normal relative to unaffected girls of similar age.
Androgen sensitivity has been linked to the number of CAG (glutamine) and GGC (glycine) repeats in the transactivator domain of the androgen receptor.
In this study, 42 girls with hypertrichosis (patients), aged between 2 and 8 years, had a similar number of CAG and GGC repeats to 29 girls of similar age without hypertrichosis (controls). However, they were significantly more likely to carry haplotypes 1 and 2, which have been linked to androgen sensitivity.
Haplotype 1 (<22CAG + 17/17GGC) was present in 28.6% of patients compared with 13.8% of controls, and haplotype 2 (<14CAG + 17/18GGC) was present in 7.1% versus 0.0%.
However, the girls with hypertrichosis had normal androgen levels, supporting the notion that they develop hypertrichosis because of increased androgen sensitivity, say lead researcher Maria Hernandez (University of Chile, Santiago) and colleagues.
Levels of other hormones were also similar between patients and controls, except for sex hormone-binding globulin (SHBG), which was significantly reduced in patients (71 vs 82 nmol/L). When girls with hypertrichosis were divided by androgen receptor haplotype, the SHBG reduction was limited to those with the non-androgen-sensitive haplotypes 3, 4 and 5.
“This hormonal pattern may lead to the development of hypertrichosis due to a higher free androgen index”, the team writes in the International Journal of Pediatric Endocrinology.
Girls with hypertrichosis and androgen-sensitive haplotypes had significantly lower levels of androstenedione (0.2 vs 0.4 ng/mL), dehydroepiandrosterone sulfate (38.0 vs 161.0 ng/mL) and anti-Müllerian hormone (AMH; 41.6 vs 23.8 pmol/L) relative to those with non-androgen-sensitive haplotypes. They also had increased levels of inhibin B (18.9 vs 8.3 pg/mL) relative to controls with androgen-sensitive haplotypes.
“The higher AMH and inhibin B levels observed in these patients, suggests that they appear to have a higher number of small antral follicles, as observed in patients with [polycystic ovary syndrome]”, says the team.
By Eleanor McDermid, Senior medwireNews Reporter