Many males may have concerns about the size or appearance of their penis from time to time. People may wonder if penis size is genetic. We address whether this, and any other factors, play a role in determining penis size.
While it is true that people can consider penis size to be a genetic trait, many other factors impact penis size. These factors include hormones, nutrition, and diet.
In this article, we explore factors that affect penis size, average penis length, and the risks of penis enlargement methods.
Genes are the building blocks that determine a living organism’s appearance and behavior. Humans inherit two copies of each gene, one from each parent. Multiple genes make up chromosomes.
Humans have 23 pairs of chromosomes. Of these, there are 22 autosomes and one set of sex chromosomes.
A person’s sex chromosomes determine their biological sex and secondary sexual characteristics.
Males inherit one Y chromosome from their male parent and one X chromosome from their female parent. Females inherit two X chromosomes, one from each parent.
The Y chromosome carries genes that oversee the development of male genitalia and fertility.
The Y chromosome determines the development of the penis and testes but not necessarily penis size or girth. These characteristics may be dependent on the X chromosome.
The X chromosone contains 900–1,400 genesTrusted Source, whereas the Y chromosome houses only about 70–200 genesTrusted Source.
This difference may explain why penis size varies among siblings with the same biological parents.
Genetic mutations may also affect penis size and appearance as well as other physical characteristics.
While quite rare, genetic conditions sometimes influence penis size include Kallmann syndrome and Klinefelter syndrome.
Thus, penis size depends on a combination of a person’s parental genes, their own unique genes, and other external factors.
Other factors that affect size
The following factors also affect penis size:
Hormones
Just as estrogen and progesterone affect female sexual characteristics, such as breasts, hips, and fat storage, male sex hormones, or androgens, contribute to testicular and penile growth.
During puberty, the pituitary gland produces more luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
LH promotes testosterone production in the Leydig cells of the testicles, and FSH promotes sperm production.
Variations in testosterone levels during pregnancy may cause penile abnormalities. For example, the mother may not produce enough human chorionic gonadotrophin (hCG) hormone. The hCG hormone stimulates testosterone development in the fetus.
Rare conditions, such as 5 alpha reductase deficiency and congenital adrenal hyperplasia, also affect testosterone levels and may affect genital appearance.
Even if testosterone levels are normal, some medical conditions may stop a person’s body from responding to testosterone correctly. This response is called androgen insensitivity.
When any of these hormonal issues arise, the penis of a male fetus may not develop in the usual way.
Environment
Environmental pollutants, such as pesticides, plasticizers, and other chemicals, may have a negative effect on penis size. These chemicals may act as endocrine disruptorsTrusted Source and impact gene and hormone expression.
Epigenetics is a growing area of science investigating how the environment may affect gene expression.
ResearchersTrusted Source believe epigenetics plays a role in development and disease. They suspect it may influenceTrusted Source hormone function and have a role in hormone disorders.
Studies in 2015Trusted Source and 2016Trusted Source both suggest that prenatal exposure to chemicals, such as phthalates, negatively impacts the genital development of male newborns.
A 2019 study also suggests that epigenetic-associated dietary influences may slow genital progression in adolescent boys.
Nutrition
Malnutrition in the womb and throughout life may impact hormones and affect growth and development.
Furthermore, malnutrition in adolescence, as is seen in anorexia or bulimia, can delayTrusted Source normal puberty.
While individuals undergoing delayed puberty typically catch up eventually, symptoms of delayed puberty include a smaller penis and testicles.
Other factors
Genetics are the strongest predictors of penis size. However, factors, such as body fat and the presence or absence of pubic hair, can make the penis appear larger or smaller without affecting its true size.
When exposed to cold temperatures, the blood vessels in the penis constrict. This physiological reaction causes the penis to shrink temporarily.
