Male fertility problems are determined in the womb, research
from the University of Edinburgh suggests.
Common genital disorders, low sperm count and testicular
cancer could all be linked to hormone levels early in
pregnancy, studies in rats suggest.
It was found that levels of male hormones, such as testosterone,
in a critical "window" at 8-12 weeks determine future
The results are published online in the Journal of Clinical
Problems with reproductive development such as the testes
not descending properly into the scrotum (cryptorchidism)
or the urinary tract opening in the wrong place on the
penis (hypospadias) are fairly common in young boys.
Other disorders, such as low sperm counts and testicular
cancer, are thought to be part of the same pathway.
Using the mouse model, researchers at the Medical Research
Council Human Reproductive Sciences Unit found the disorders
resulted from low levels of male hormones - or androgens
- at the equivalent to 8-12 weeks human gestation.
They also found that the level of androgen hormone at
this time was related to the distance between the base
of the penis and the anus.
This measurement could be an early warning system of
future reproductive problems in baby boys, they said.
It could also give insights into links between hormones
in the womb and fertility problems in later life.
Study leader, Dr Michelle Welsh, said: "We know from
other studies that androgens work during foetal development
to programme the reproductive tract.
"But our assumption was that it would be much later
She added the anogenital measurement would be a useful
"Say a clinician were to examine a 30-year-old man with
testicular cancer - previously there would have been no
way of knowing what hormones he was exposed to in the
"We would suggest that this measurement, even at this
later stage in life, could offer an indication of hormone
"For example, the shorter the distance, the less confident
we can be that hormones have acted correctly and at the
Co-author, Professor Richard Sharpe, said around 7%
of boys had cryptorchidism and low sperm counts affect
as many as one in five young men.
Dr Allan Pacey, senior lecturer in andrology at the
University of Sheffield, said scientists had been worried
for many years about the increasing incidence of problems
resulting from disrupted development of the male reproductive
system during pregnancy.
"Understandably, this is almost impossible to study
in humans directly and so animal models are needed to
unravel the precise details.
"To use the adult anogenital distance as a proxy marker
of foetal exposure in utero is a good suggestion and I
would encourage studies to investigate how well this correlates
with problems of the male reproductive system."