The Science Of Sexual Development
Key Takeaways
A hormone has to be able to bind the receptor and take action on target cells to be effective
Testosterone and estrogen can travel into cells and interact with the DNA of cells to control gene expression
Primary sexual characteristics show up at birth (external genitalia) while secondary sexual characteristics take place during puberty (deepening of the voice, hair growth, etc.)
Masculinization of the brain in males and females is accomplished by estrogen via aromatase which converts testosterone to estrogen
Estrogen sets up masculine circuitry in the brain, testosterone controls the display of behaviors
In utero exposure to androgens may have an impact on mate selection and sexual orientation later in life
Pre-conception and in utero exposure to certain substances can impact the sexual characteristics of the fetus
The average density and volume of human sperm has decreased significantly in the U.S. and Europe
Hormone Overview And Development Of Fetus
Definition of hormone: released in one area of the body (usually from a gland) that travel and have effects on that gland and other tissues in the body
Hormones have direct effects on the brain, body, and spinal cord
Androgen: category of hormones, including testosterone
Chromosomal sex: in general – the XY chromosome is male and XX chromosome is female
Y chromosome has genes that suppress female reproductive organs, promote the formation of testes, inhibit müllerian ducts
The placenta itself is an endocrine organ
Gonadal sex: in general – if gonads are testes then the fetus is male; if gonads are ovaries then the fetus is female
Steroid sex: effect of steroid hormones (i.e., testosterone and estrogen) on traits such as the shape of the baby, human, genitalia, jaw
What Hormones Do
The hormone has to be able to bind the receptor and take action on target cells to be effective
Hormones have two categories of effects: fast and slow in terms of the effect on genes
Fast-acting hormones: cortisol, adrenaline
Slow-acting hormones: testosterone, estrogen – can signal and attach to a cell to induce quick effects but generally have long-term effects
Testosterone and estrogen can travel into cells and interact with the DNA of cells to control gene expression
Effects of hormones are seen in primary sexual characteristics (the ones you’re born with) and secondary sexual characteristics (show up in puberty)
Primary Sexual Characteristics In Males
Primary sexual characteristics show up at birth – external genitalia which defines sex
Enzyme dihydrotestosterone is actually what’s responsible for the development of the penis in baby’s that have an X and Y chromosome – not testosterone
Dihydrotestosterone masculinizes primary sex characteristics
The brain has receptors for testosterone and estrogen
Masculinization of the brain is not accomplished by testosterone
Masculinization of the brain is accomplished by estrogen, not testosterone – testosterone is converted to estrogen by an enzyme called aromatase (made by body fat and neurons in the brain)
Estrogen sets up masculine circuitry in the brain, testosterone controls the display of behaviors later in life
Secondary Sexual Characteristics In Males
Testosterone is involved in the development of secondary sexual characteristics – deepening of the voice, growth of pubic hair
Dihydrotestosterone is responsible for facial hair but also lack of hair on the head
Speed of entry and exit from puberty might be worthwhile to study correlation to aging and longevity arc
In-Utero Effects Of Hormones On Sexual Preference
Study: young males (versus young females) have more auto-acoustic emissions as picked up by the device
Females who identify as lesbians had comparable auto-acoustic emission to males
In utero exposure to androgens may have an impact on sexual preference
This type of study has been replicated approximately six times and has shown interesting correlations
It’s possible the brain organizes early and impacts same- or the opposite- sex choices later in life
Environmental Factors In Sexual Characteristics
Maternal use of evening primrose oil and skin contact with infant or young males accelerated breast bud development
Primrose oil promoted estrogenic activity in the body
Atrazine exposure in water causes severe testicular malformation in the organ
Herbicides have negative effects by impacting the ratio of hormones in the mother or testes or father – and – direct effects altering fetus
The average density and volume of human sperm has decreased significantly in the U.S. and Europe
Lifestyle Factors In Sexual Characteristics & Child Development
THC and other things in cannabis promote significant activity in aromatase (which converts testosterone to estrogen)
Pot smokers have a higher rate of development of gynecomastia (male development of breasts)
Smoking marijuana during pregnancy can promote more circulating estrogen in the body of developing fetus
No peer-reviewed, quality studies that cell phones are bad for the brain – but – there is evidence of defects in ovarian and testicular development
Cell phone storage in males: chronic exposure to cell phone emitted waves on gonads could impact swimming speed and density, and testosterone levels
Cell phone storage in females: chronic exposure to cell phone emitted waves can impact estrogenic levels and regularity of cycle, and prolactin levels
Creatine promotes balding in some males because of its effects on dihydrotestosterone