Hormones and Gender
Chromosomes initially determine a person’s sex
but most gender development is actually
governed by hormones. They are produced both
prenatally (e.g. testosterone) and in adolescence
(puberty).Hormones influence the development of
genitalia and/or affect the development of the
brain, both of which influence gender behaviour.
Testosterone is the male sex hormone which is
produced by the testes and contributes to the
development of the male reproductive system.
Testosterone initiates the process of puberty
including the growth of facial hair, deepening of
the voice and muscle growth.
Estrogen is the female sex hormone produced in
the ovaries and stimulates the widening of the hips,
the onset of menstruation, and the growth of sex
organs, breasts and pubic hair.
Between four and eight weeks after conception
the gonads start to release hormones. In males
the testes are instructed to release
testosterone which acts on the hypothalamus of
the brain. Without testosterone the brain would
develop in the female form (Green, 1995). In the
female, hormone release from the ovaries is
Differences in brain structure result from the
release of hormones. Geshwind and Galaburda
(1987) argue that sex differences are caused by
the release of testosterone. Male brains are
exposed prenatally to more testosterone than
female brains and this leads to a masculinised
brain. For example females are known to be better
at socialising and empathising, whereas males are
said to be better at special navigation (Hoag,
The effects of testosterone on brain development
have been tested and confirmed through animal
studies. Quadagno et al. (1997) found that female
monkeys deliberately exposed to testosterone
during prenatal development, later engaged in
more rough and tumble play than normal females.
Genetics and Gender
In the first few weeks after conception there are
no structural differences between genetically
male and genetically female embryos. Both male
and females have two rigid of tissue, called
gonadal ridges from which the male and female
sexual organs will develop. Each person has 23
chromosomes, each of these chromosomes carry
hundreds of genes containing instructions on
physical and behavioural characteristics.
One pair of chromosomes (the 23rd
) are the sex
chromosomes, because they determine an
individual’s sex. The male pair of chromosomes are
known as XY and the female pair are known as XX.
If an embryo inherits an X chromosome from both
parents it will become a girl and if it inherits an X
from the mother and a Y from the father, it will
become a boy.
There is a direct link between an individual’s
chromosomal sex (XX and XY) and their external
genitalia (vagina or penis) and internal genitalia
(ovaries and testes). During prenatal development
all individuals look the same – and embryos have
genitalia that externally look feminine.
At about 6 weeks, a gene on the Y chromosome,
the SRY gene, causes the gonads (sex organs) of
the embryo to develop as Testes. If the embryo
has no Y chromosome, it will not have the SRY
gene, without the SRY gene, the gonads will
develop as ovaries. The testes and ovaries begin
to produce different levels of sex hormones
which affect gender development.
Biology explains how an individual acquires their
sex genetically. It may also explain some aspects
of gender (a person’s sense of whether they are
male or female) because of the link between
genes and genitalia and hormones.
Babies can be born with atypical sex
chromosomes. For example some baby boys have
an extra X chromosome (XXY). Interestingly, such
boys grow up to have more feminine traits as well
as more female looking bodies. This shows that
chromosomes can have a significant on gender.