Largest study to date maps how female testosterone levels change with age
Findings show testosterone declines gradually with age - rather than dropping off around menopause
A study of 5,323 women has mapped how female testosterone levels change with age, finding that they decline steadily throughout adult life rather than falling sharply around menopause.
The research, led by UK & Ireland women’s health company Hertility and published in the Journal of Endocrinological Investigation, found testosterone declined by about 1.4% a year from a woman’s twenties onwards. The variation in levels between women also widened with age.
The findings add to previous research showing that testosterone declines progressively with age, rather than falling specifically at menopause. What the new study adds is a larger reference group and a model showing how the expected range changes year by year. Hormone test results are typically compared with reference ranges to help clinicians judge whether a result is unusual - but these can use broad age bands and relatively small populations.
“When a woman has a hormone test, she is looking for an answer about her own body,” said Dr Helen O’Neill, Hertility’s chief executive and an associate professor in reproductive and molecular genetics at UCL.
“What she receives is a comparison against an average, and too often an average drawn from a few dozen women, decades ago, grouped into age brackets so broad they are almost meaningless.”
A larger reference group
Researchers initially analysed data from 30,453 women who used Hertility’s at-home hormone testing service in England, Scotland and Wales between 2020 and 2025. They then excluded women with factors known to affect testosterone, including hormonal contraception, reproductive conditions, irregular cycles and BMI outside the study criteria, leaving 5,323 women aged 19 to 59 in the reference group.
That group is larger than those used in previous studies specifically designed to establish female testosterone reference ranges. Hertility argues that modelling levels continuously by age could give clinicians more useful context than broad age categories when interpreting an individual result.
“Precision medicine requires reference data of sufficient scale and rigour that an individual can be interpreted as an individual,” continued Dr O’Neill.
“Better reference ranges will never replace clinical judgement, but they change what clinical judgement has to work with, and set a standard for what should be expected before any hormone result is described as normal or abnormal for a woman.”
The study authors also acknowledge limitations. The women were a self-selected group who had paid for private hormone testing and may therefore differ from the wider population. They said further longitudinal research is needed to understand how testosterone changes within individual women over time.
Hirsutism linked with higher testosterone
The researchers separately analysed 2,338 women who reported hirsutism, or excess hair growth, and found they had higher testosterone levels than the reference group, particularly at younger ages. The finding supports hirsutism as a possible clinical sign of androgen excess that may warrant further investigation.
Hertility is now calling for laboratories and medical bodies to consider more age-specific reference ranges for female hormones. The researchers have published their age-specific testosterone tables alongside the study.