The way a person appears—as a girl or a boy—is not as simple as merely carrying genes associated with being male or female.
At birth, doctors (and parents) usually determine a baby’s sex based on the appearance of the external genitalia. However, in some cases, these anatomical features may not accurately reflect the child’s biological sex.
Boys and girls are biologically different—this is quite evident. Yet certain medical conditions can blur these differences. In such situations, distinguishing a child’s sex based solely on outward appearance becomes difficult. This highlights once again how complex and multifaceted human biology truly is.
The Role of Hormones
Hormones play a decisive role in shaping a person as male or female. For example, if a genetically female newborn is exposed to excessive levels of the hormone testosterone in the womb, her external genitalia may resemble male anatomy. Conversely, too little testosterone can hinder the normal development of reproductive organs in a genetically male infant.
Testosterone and other male hormones influence not only the development of the genitalia but also many other organ systems, including the kidneys, urinary system, and most importantly, the brain. At birth and throughout life, the size and function of certain brain regions may differ between males and females.
How Does Testosterone Increase in the Female Womb?
Testosterone belongs to a group of male sex hormones known as androgens. This raises an important question: how and why can this hormone increase in the female womb?
In some cases, a mother may be exposed to medications containing testosterone during pregnancy. More commonly, however, the cause is genetic mutations. These mutations can signal the fetus’s body to produce excessive amounts of testosterone or to produce it at inappropriate times. It is important to note that both male and female bodies produce testosterone, but in different quantities.
Such hormonal imbalances can sometimes lead to small but critical changes in a baby’s development.
Differences of Sex Development (DSD)
When these changes occur at a very early stage of development, a baby may be born with a condition known as Differences (or Disorders) of Sex Development (DSD).
Important note:
There is no scientific evidence demonstrating a direct link between DSD and transgender identity.
One expert who emphasizes the rarity of DSD cases is William Reiner, a child and adolescent psychiatrist as well as a pediatric urologist. He specializes in developmental disorders affecting the urinary tract and the male reproductive system.
The Most Studied DSD: Congenital Adrenal Hyperplasia (CAH)
One of the best-studied forms of DSD is congenital adrenal hyperplasia (CAH). The adrenal glands—small, grape-sized organs present in everyone—produce small amounts of testosterone. However, a specific genetic mutation can cause these glands to produce excessive levels of androgens.
This mutation usually does not affect boys, as their bodies already produce high levels of androgens. However, girls born with CAH may appear physically male, and in some cases, their reproductive anatomy may resemble that of a male. This condition is medically referred to as intersex.
In severe cases, a genetically female infant may appear completely male at birth. Sometimes, infants born with characteristics of both sexes undergo surgical intervention shortly after birth. In other cases, doctors and parents must work together to decide which sex will be assigned to the child.
Other Genetic Factors
Some genetic mutations prevent the body from producing enzymes necessary for the synthesis of DHT (dihydrotestosterone). DHT is a more potent androgen than testosterone and plays a crucial role in the development of male genitalia. A deficiency in this enzyme can cause a genetically male infant’s genitalia to appear partially or completely female.
Conclusion
William Reiner summarizes the issue as follows:
“You cannot definitively determine whether a child is biologically male or female based solely on the appearance of the genitalia.”
This reality clearly demonstrates how complex, multilayered, and individual human biology truly is.