The interactions of hormones and sexual behavior affect the determination of gender identity
and remain difficult and dubious tasks. Apparently, gender identity is usually consistent with
chromosomal sex and anatomical sexual development (Pinel, 2009). Men and women differ in
their physical attributes, reproductive function, and thought process (Meyers, 2011). Although
displaying patterns of behavioral and cognitive differences, hormonal influences on brain
development are apparent (Pinel, 2009). Understanding brain morphology, sexual differentiation,
gender roles, and gender identity continue to add knowledge toward the answers society assumes
while evaluating the role of experience independent of physiological predisposition continues.
In contrast, evidence recently accumulated suggests the environment responds differently to
the pre- wired brains in boys and girls (Myers, 2011). Fundamentally, flawed is mamawawa, the
misconception that men-are-men and women-are-women (Pinel, 2009). The biological bases of
sex differences in brain and behavior have become much, better known through increasing
numbers of behavioral, neurological, and endocrinological studies. Sex refers to biological traits
whereas gender is sociological. Biological factors include genetics and a complex interaction
among prenatal hormonal activity whereas the issue of „nature versus nurture‟ discusses
psychosocial factors (Pinel, 2009).
Sexual differentiation is the process by which males and females develop distinct
reproductive anatomy (Rathus, Nevid, & Fichner-Rathus, 2010). According to Pinel (2009),
“One could say that the basic blueprint of the human embryo is female,” (p. 435). The embryo
deviates from the female developmental course with the instructions from the Y chromosome
(Pinel, 2009). The SRY (sex-determining region Y gene) binds to the strand of genes called
DNA and distorts it (Developmental Origins of Health and Disease, 2012) . This distortion leads
to the formation of the testes (Pinel, 2009).
According to DOHaD (2012), “The cortex of the primordial gonad develops into an ovary
if no Y chromosome exists whereas under the influence of the Y chromosome, the medulla of
the primordial gonad develops into a testis,” (para 18). Unfortunately, mixed gender is the
result of confusion with H-Y antigen entering a male fetus causing ovaries or a genetic female
with testes (Pinel, 2009). In addition, the third month of fetal development determines
testosterone stimulation and Mullerian-inhibiting substance (MIS) that causes the Mullerian
system to degenerate activating dissention of the testes into the scrotum (Rathus, Nevid, &
Fichner-Rathus, 2010). Confusion of this fetal period can cause development of female
reproductive ducts along with male ones (Pinel, 2009). Concurrently, in theory, testosterone is
responsible for the external genitals (Pinel, 2009).
According to Pinel (2009), “Steroid hormones play the major role in sexual development,”
(p. 315). Synthesized from cholesterol, steroid hormones easily penetrate cell membranes,
bind to receptors in the cytoplasm of the nucleus, and directly affect gene expression (Pinel,
2009). Once formed the testes (gonads) and ovaries begin to produce androgens and estrogens
with estradiol the most common estrogen and testosterone the most common androgen (Pinel,
2009). In addition, the adrenal cortex releases not only the principal steroid hormones but also
small amounts of the same sex steroids released by the gonads (Pinel, 2009). Concurrently,
the hypothalamus regulates the anterior pituitary gland while regulating the 28-day cycle
experienced by females (Pinel, 2009). The cycle involves levels of gonadal and gonadotropic
hormones preparing the female reproductive system (Pinel, 2009).
Researchers today continue developing the connections between brain dimorphisms and
sex chromosomes. Aromatization is the process causing a slight change of a testosterone
molecule to a benzene ring (Pinel, 2009) converting testosterone to estradiol affecting the
masculinization of the brain by testosterone. According to Pinel, “Volumetric differences
between particular structures develop by preferential apoptotic cell loss, not cell growth,” (p.
325). Biological views focus on the possible affect of hormones on the brain during prenatal
development and the specialized hemispheres within the brain (Meyers, 2011). In theory,
prenatal hormones may masculinize or feminize the brain during development. According to
research, left-handed people are right brain dominant (Pinel, 2009). Scientific research
regarding the release of testosterone into the right-hemisphere during prenatal development
investigates the theory that testosterone may cause masculine influence onto right-brained
female (DOHaD, 2012).
In contrast, hormonal errors produce various congenital defects during prenatal
development (Pinel, 2009). As stated earlier, gender identity is usually consistent with
chromosomal assignment. However, gender assignment (sex assignment) is labeling a
newborn female or male regardless of the fetal brain‟s exposure to androgens in the uterus
(Pinel, 2009). From birth, hermaphrodites have ovarian and testicular tissue, possibly one
gonad of each sex (Pinel, 2009). Congenital adrenal hyperplasia is a form of intersexualism
where a genetic (XX) female with internal female ovaries (Rathus, Nevid, & Fichner-Rathus,
2010) displays masculinize external genitals and displays a clitoris enlarged resembling a
small male penis (Berenbaum & Hines, 1992; Zucker, 1999; as cited on p. 176).
In contrast, genetic (XY) males with sensitivity to androgens receive feminized external
genital, including a small vagina, undescending testes, no sparse pubic or underarm hair, and
feminized breasts (Adachi, 2000; Hughes, 2000 as cited in Pinel, 2009, p. 339). Because the
testes produce MIS (Mullerian inhibiting substance) prevention of the development of a
uterus or fallopian tubes exists (Rathus, Nevid, & Fichner-Rathus, 2010).
Environmental influences include a set of behavior expectations (norms) for males and
females, gender roles across generations, and expectations of what society labels as
normal and acceptable ideas, attitudes, behaviors, and traditions (Pinel, 2009). According
to Rathus, Nevid, & Fichner, 2005, “Gender identity is our psychological awareness or
sense of being male or being female and one of the most obvious and important aspects of
our self-concepts.” The gender difference is evident early in life before culture has much
effect (Rathus, Nevid, & Fichner-Rathus, 2010). Unfortunately, clearly defined within our
society is the connection between sexual behavior and gender roles.
Little girls are taught to be submissive always waiting for the male‟s first approach.
Children become aware of their anatomical sex by the age of 18 months and by the age of
36 months, most have a firm sense of their gender identity (Pinel, 2009). Children learn to
categorize themselves by gender very early in life. Behavior expectations and differences
such as, men repair things whereas women clean up things define gender roles (Myers,
2010). Judging from scientific studies it appears that our society still believes in sex-role
(gender identity) theory, which says that we humans learn from society's institutions to
behave in ways appropriate to our sex (Meyers, 2011). Studies indicate that women are
biologically less sexual than are men. Because of society‟s stigma placed upon the
sexually active female, it is difficult to achieve an accurate reading regarding female
sexuality. Subsequently, time bends the gender roles as shown by the amount of females
acquiring medical and law degrees. In addition, women in politics are a dramatic cultural
change over a remarkably short time.
Clinical implications and progress of gender variations, hormones, and gender identity
are evident in The Case of the Little Girl Who Grew up to Be a Boy (Money & Ehrhardt,
1972 as cited in Pinel, 2009, p. 328). Raised as a little girl, male secondary sex
characteristics began developing at the onset of puberty (Pinel, 2009). Because of
scientific progress, the patient received surgical procedures decreasing the size of her
clitoris and increasing the size of her vagina. Suppressing androgens allowing her own
estrogen to circulate feminized her body allowing her to enjoy a normal sex life and happy
marriage (Money & Ehrhardt, 1972 as cited in Pinel, 2009, p. 328).
Biopsychology emphasizes that body type, sexual or gender identity, and sexual
attraction are sometimes unconnected (Pinel, 2009). Sexual identity, sexual orientation,
and sexual body formations are often independent combining femaleness and maleness
discounting the outdated, fundamentally incorrect theory of mamawawa, men-are-men,
and women-are-women. Biology and culture interact as advances in genetic science
indicate how experience uses genes to change the brain (Quarts & Sejnowski, 2002, as
cited in Myers, 2010, p. 223). Today, scientific research continues to show the female
brain and the male brain develops differently with various mechanisms, at different times
with variations in genetics and hormones creating a variety of sexually independent and
sexually interconnected male and female individuals (Pinel, 2009).
Developmental Origins of Health and Disease (DOHaD). (2012). Endocrine and reproductive
system. Retrieved from
Myers, D. (2011). Exploring social psychology (6th ed.). Boston, MA: McGraw-Hill.
Pinel, J. (2009). Biopsychology (7th ed.). Boston, MA: Allyn & Bacon.
Rathus, S., Nevid, J., & Fichner-Rathus, L. (2010). Human sexuality: In a world of diversity (7th
ed.). Boston, MA: Allyn & Bacon.