Table of ContentsView AllTable of ContentsSex ChromosomesSpecific GenesGenetic DisordersEnvironmental ToxinsMalnutritionOther Factors
Table of ContentsView All
View All
Table of Contents
Sex Chromosomes
Specific Genes
Genetic Disorders
Environmental Toxins
Malnutrition
Other Factors
Genetics plays a significant role in the size of the penis, but it is not the only factor. Nutritional deficiencies and environmental toxins can impact thedevelopment of the penisinside and outside of the womb. Variations in the production oftestosteronecan also affect the development of the penis during puberty.
Your body size, type, and weight can influence the appearance and perception of penis size, potentially making your penis appear smaller even if it is ofaverage (or above average) length.
A Note on Gender and Sex TerminologyVerywell Health acknowledges thatsex and genderare related concepts, but they are not the same. To accurately reflect our sources, this article uses terms like “male," “female,” “father,” and “mother” as the sources use them.
A Note on Gender and Sex Terminology
Verywell Health acknowledges thatsex and genderare related concepts, but they are not the same. To accurately reflect our sources, this article uses terms like “male," “female,” “father,” and “mother” as the sources use them.
How Sex Chromosomes Influence Penis Size
Your mother has two X chromosomes, and your father has an X and Y chromosome. To be biologically male, you would need to inherit one X chromosome from your mother and one Y chromosome from your father. Each chromosome contributes to penis size either directly or indirectly.
How the Y Chromosome Contributes
It is the testicles that produce testosterone in males. This is the hormone that directs the development of secondary male characteristics during puberty, including a larger bone mass, the formation of the Adam’s apple, facial and body hair, and the size of the adult penis.
Although the SRY gene doesn’t inherently influence the size of testicles, mutations of the gene can lead to underdeveloped testicles. This, in turn, can reduce the amount of testosterone produced during puberty, along with the ultimate size of the penis.
How the X Chromosome Contributes
The X chromosome inherited from a mother contains between 900 to 1,400 genes. Of them, a gene calledandrogen receptor (AR) geneplays a direct role in the development of the penis.
The AR gene determines whether tissues contain specialized proteins—called androgen receptors (ART)—that testosterone can attach to. Both males and females have androgen receptors, but males have more of them.
During early development, an embryo will develop an outgrowth of tissue called thegenital tubercle. The AR gene directs whether the tubercle has AR receptors or not. If it does, the tubercle willform into a penisandscrotum; if not, the tubercle will form avaginaandclitoris.
Although the AR gene does not direct how big the penis will grow, certain mutations can increase the accumulation of AR receptors on the genital tubercle, which can influence penis size.
Genes That Influence Testosterone Production
While the AR gene triggers the formation of a penis, it only plays a partial role in the size of the penis. For this, testosterone plays a more central role—not only during fetal development but also during a period just after birth known as “mini-puberty.”
Mini-puberty spans the first three to six months of life during which sex hormones—testosterone in males andestrogenin females—are exceptionally high. It is the phase when the sex organs mature and, in males, the eventual length and size of the penis are established.
Certain genes are thought to influence mini-puberty, including:
DHT is the hormone that chiefly influences the development of the penis during mini-puberty and puberty (between the ages of 9 and 14). While the amount of DHT doesn’t solely determine penis size, a lack of DHT certainly can.
When Does a Penis Start and Stop Growing?The penis will grow proportionately from mini-puberty onward but then experience a sudden growth spurt during puberty, typically around age 12. At this age, thehypothalamusandpituitary glandin the brain release a hormone calledluteinizing hormone (LH)that stimulates the production of testosterone from the testicles.The growth of the penis will continue until the end of puberty, typically between the ages of 18 and 21.
When Does a Penis Start and Stop Growing?
The penis will grow proportionately from mini-puberty onward but then experience a sudden growth spurt during puberty, typically around age 12. At this age, thehypothalamusandpituitary glandin the brain release a hormone calledluteinizing hormone (LH)that stimulates the production of testosterone from the testicles.The growth of the penis will continue until the end of puberty, typically between the ages of 18 and 21.
The penis will grow proportionately from mini-puberty onward but then experience a sudden growth spurt during puberty, typically around age 12. At this age, thehypothalamusandpituitary glandin the brain release a hormone calledluteinizing hormone (LH)that stimulates the production of testosterone from the testicles.
The growth of the penis will continue until the end of puberty, typically between the ages of 18 and 21.
Congenital Disorders That Affect Penis Size
Congenital disorders like Kallmann syndrome and 5-alpha reductase deficiency can lead to an abnormally small penis, known as amicropenisor microphallus. A micropenis is defined as being at least 2.5 standard deviations (variation from the mean) smaller than the mean (average) penis size in adults.
This translates to a stretched penis length of 3.67 inches compared to the mean stretched penis length of 5.21 inches.
Micropenis is a rare condition that affects only 1.5 per 10,000 children in the United States.
Environmental toxins like pesticides, pollutants, and industrial chemicals can also disrupt theendocrine (hormonal) system, including the production of testosterone.
Exposure to these toxins, called “endocrine disruptors,” before and after birth has been shown to affect sexual development in boys and adolescents, including the development of the penis during puberty.
One of the most common examples is a chemical calleddiethylhexyl phthalate(DEHP) used in the production of soft plastics. A 2024 study published inPediatric Researchshowed that exposure to DEHP during pregnancy was linked to a smaller penis length and width in male offspring.
An earlier study from Mexico reported that mothers exposed to a similar chemical calledmono-2-ethylhexyl phthalatealso had male babies with abnormally smaller penises.
Nutritional Factors
Malnutritionduring pregnancy can affect normal fetal development and, according to certain animal studies, may also affect the sexual maturation of males in later life.
Prior to puberty, malnutrition associated witheating disordersin boys, includingbulimia nervosaoranorexia nervosa, has been shown to delay puberty and sexual maturation.This suggests that any form of severe malnutrition before the onset of puberty may have the same effect.
While research into the impact of nutrition on penis growth is lacking, a 2021 study in theJournal of Clinical Endocrinology and Metabolismreported that male infants fed soy formula had had a more rapid increase in penile length during mini-puberty than those fed cow’s or breast milk.
In some cases, theactualsize of a penis and theperceivedsize of a penis are mismatched. For instance, people who are extremely tall may be perceived to have a smaller penis than someone with the same-sized penis who is short.
What Is the Average Size of a Penis?
The average penis size may be smaller than some people realize. Epidemiologic studies of adult males report the average flaccid (soft)penislength from the base to the tip is 3.4 inches, while the average erect (hard) penis length is 5.5 inches.
And, despite popular belief, penis size has no relationship to one’s height, shoe size, or nose size.
Summary
Genetics plays a role in the size of a penis. This includes certain genes on the X and Y chromosomes that direct the formation of the testicles and penis. Other genes, like the MKRN3 and KISS1R genes, regulate testosterone production, while the SRD5A2 gene regulates the conversion of testosterone into its active form, known as dihydrotestosterone (DHT).
Other factors influencing penis size include congenital disorders like Kallman syndrome and 5-alpha reductase deficiency, exposure to industrial toxins like diethylhexyl phthalate (DEHP), and malnutrition before and after birth.
15 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.MedlinePlus.SRY gene.Akcan N, Uyguner O, Bas F, et al.Mutations in AR or SRD5A2 genes: clinical findings, endocrine pitfalls, and genetic geatures of children with 46,XY DSD.J Clin Res Pediatr Endocrinol.2022 Jun;14(2):153–71. doi:10.4274/jcrpe.galenos.2022.2021-9-19Lanciotti L, Cofini M, Leonardi A, Penta L, Esposito S.Up-to-date review about minipuberty and overview on hypothalamic-pituitary-gonadal axis activation in fetal and neonatal life.Front Endocrinol (Lausanne).2018;9:410. doi:10.3389/fendo.2018.00410Khan L.Puberty: onset and progression.Pediatr Ann. 2019;48(4):e141-e145. doi:10.3928/19382359-20190322-01MedlinePlus.Kallmann syndrome.Genetic and Rare Diseases Information Center.Congenital adrenal hyperplasia (CAH).Gunasekaran K, Khan SD.Micropenis. In:Sexual Medicine: Principles and Practice. New York, NY: Springer; 2019:113-20.Salvi NB, Ghassabian A, Brubaker SG, et al.Prenatal phthalate exposure and fetal penile length and width.Pediatr Res.2024 May;95(6):1587–1595. doi:10.1038/s41390-023-02939-xBustamante-Monte LP, Hernandez-Valero MA, Flores-Pimental D. et al.Prenatal exposure to phthalates is associated with decreased anogenital distance and penile size in male newborns.J Dev Orig Health Dis. 2013 Aug;4(4):10.1017/S2040174413000172. doi:10.1017/S2040174413000172Matsuzaki T, Munkhzaya M, Tungalgsuvd A, et al.Prenatal undernutrition disrupted the sexual maturation, but not the sexual behavior, in male rats.Reprod Med Biol. 2017 Oct;16(4):325–329. doi:10.1002/rmb2.12045Soliman A, De Sanctis V, Elalaily R.Nutrition and pubertal development.Indian J Endocrinol Metab.2014 Nov;18(Suppl 1):S39–S47. doi:10.4103/2230-8210.145073Chin HB, Kelly A, Adgent MA.Reproductive hormone concentrations and associated anatomical responses: does soy formula affect minipuberty in boys?J Clin Endocrinol Metab. 2021 Aug 18;106(9):2635-45. doi:10.1210/clinem/dgab354Cohen PR.Adult acquired buried penis: a hidden problem in obese men.Cureus.2021 Feb;13(2):e13067. doi:10.7759/cureus.13067Belladelli F, Giudice FD, Glover F, et al.Worldwide temporal trends in penile length: a systematic review and meta-analysis.World J Mens Health. 2023. doi:10.5534/wjmh.220203Alves Barboza R, Da Silva EA, Ruellas T, Damião R.Anthropometric study of penile length in self-declared Brazilians regarding the color of the skin as White or Black: the study of a myth.Int J Impot Res. 2018;30(1):43-7. doi:10.1038/s41443-017-0009-z
15 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.MedlinePlus.SRY gene.Akcan N, Uyguner O, Bas F, et al.Mutations in AR or SRD5A2 genes: clinical findings, endocrine pitfalls, and genetic geatures of children with 46,XY DSD.J Clin Res Pediatr Endocrinol.2022 Jun;14(2):153–71. doi:10.4274/jcrpe.galenos.2022.2021-9-19Lanciotti L, Cofini M, Leonardi A, Penta L, Esposito S.Up-to-date review about minipuberty and overview on hypothalamic-pituitary-gonadal axis activation in fetal and neonatal life.Front Endocrinol (Lausanne).2018;9:410. doi:10.3389/fendo.2018.00410Khan L.Puberty: onset and progression.Pediatr Ann. 2019;48(4):e141-e145. doi:10.3928/19382359-20190322-01MedlinePlus.Kallmann syndrome.Genetic and Rare Diseases Information Center.Congenital adrenal hyperplasia (CAH).Gunasekaran K, Khan SD.Micropenis. In:Sexual Medicine: Principles and Practice. New York, NY: Springer; 2019:113-20.Salvi NB, Ghassabian A, Brubaker SG, et al.Prenatal phthalate exposure and fetal penile length and width.Pediatr Res.2024 May;95(6):1587–1595. doi:10.1038/s41390-023-02939-xBustamante-Monte LP, Hernandez-Valero MA, Flores-Pimental D. et al.Prenatal exposure to phthalates is associated with decreased anogenital distance and penile size in male newborns.J Dev Orig Health Dis. 2013 Aug;4(4):10.1017/S2040174413000172. doi:10.1017/S2040174413000172Matsuzaki T, Munkhzaya M, Tungalgsuvd A, et al.Prenatal undernutrition disrupted the sexual maturation, but not the sexual behavior, in male rats.Reprod Med Biol. 2017 Oct;16(4):325–329. doi:10.1002/rmb2.12045Soliman A, De Sanctis V, Elalaily R.Nutrition and pubertal development.Indian J Endocrinol Metab.2014 Nov;18(Suppl 1):S39–S47. doi:10.4103/2230-8210.145073Chin HB, Kelly A, Adgent MA.Reproductive hormone concentrations and associated anatomical responses: does soy formula affect minipuberty in boys?J Clin Endocrinol Metab. 2021 Aug 18;106(9):2635-45. doi:10.1210/clinem/dgab354Cohen PR.Adult acquired buried penis: a hidden problem in obese men.Cureus.2021 Feb;13(2):e13067. doi:10.7759/cureus.13067Belladelli F, Giudice FD, Glover F, et al.Worldwide temporal trends in penile length: a systematic review and meta-analysis.World J Mens Health. 2023. doi:10.5534/wjmh.220203Alves Barboza R, Da Silva EA, Ruellas T, Damião R.Anthropometric study of penile length in self-declared Brazilians regarding the color of the skin as White or Black: the study of a myth.Int J Impot Res. 2018;30(1):43-7. doi:10.1038/s41443-017-0009-z
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
MedlinePlus.SRY gene.Akcan N, Uyguner O, Bas F, et al.Mutations in AR or SRD5A2 genes: clinical findings, endocrine pitfalls, and genetic geatures of children with 46,XY DSD.J Clin Res Pediatr Endocrinol.2022 Jun;14(2):153–71. doi:10.4274/jcrpe.galenos.2022.2021-9-19Lanciotti L, Cofini M, Leonardi A, Penta L, Esposito S.Up-to-date review about minipuberty and overview on hypothalamic-pituitary-gonadal axis activation in fetal and neonatal life.Front Endocrinol (Lausanne).2018;9:410. doi:10.3389/fendo.2018.00410Khan L.Puberty: onset and progression.Pediatr Ann. 2019;48(4):e141-e145. doi:10.3928/19382359-20190322-01MedlinePlus.Kallmann syndrome.Genetic and Rare Diseases Information Center.Congenital adrenal hyperplasia (CAH).Gunasekaran K, Khan SD.Micropenis. In:Sexual Medicine: Principles and Practice. New York, NY: Springer; 2019:113-20.Salvi NB, Ghassabian A, Brubaker SG, et al.Prenatal phthalate exposure and fetal penile length and width.Pediatr Res.2024 May;95(6):1587–1595. doi:10.1038/s41390-023-02939-xBustamante-Monte LP, Hernandez-Valero MA, Flores-Pimental D. et al.Prenatal exposure to phthalates is associated with decreased anogenital distance and penile size in male newborns.J Dev Orig Health Dis. 2013 Aug;4(4):10.1017/S2040174413000172. doi:10.1017/S2040174413000172Matsuzaki T, Munkhzaya M, Tungalgsuvd A, et al.Prenatal undernutrition disrupted the sexual maturation, but not the sexual behavior, in male rats.Reprod Med Biol. 2017 Oct;16(4):325–329. doi:10.1002/rmb2.12045Soliman A, De Sanctis V, Elalaily R.Nutrition and pubertal development.Indian J Endocrinol Metab.2014 Nov;18(Suppl 1):S39–S47. doi:10.4103/2230-8210.145073Chin HB, Kelly A, Adgent MA.Reproductive hormone concentrations and associated anatomical responses: does soy formula affect minipuberty in boys?J Clin Endocrinol Metab. 2021 Aug 18;106(9):2635-45. doi:10.1210/clinem/dgab354Cohen PR.Adult acquired buried penis: a hidden problem in obese men.Cureus.2021 Feb;13(2):e13067. doi:10.7759/cureus.13067Belladelli F, Giudice FD, Glover F, et al.Worldwide temporal trends in penile length: a systematic review and meta-analysis.World J Mens Health. 2023. doi:10.5534/wjmh.220203Alves Barboza R, Da Silva EA, Ruellas T, Damião R.Anthropometric study of penile length in self-declared Brazilians regarding the color of the skin as White or Black: the study of a myth.Int J Impot Res. 2018;30(1):43-7. doi:10.1038/s41443-017-0009-z
MedlinePlus.SRY gene.
Akcan N, Uyguner O, Bas F, et al.Mutations in AR or SRD5A2 genes: clinical findings, endocrine pitfalls, and genetic geatures of children with 46,XY DSD.J Clin Res Pediatr Endocrinol.2022 Jun;14(2):153–71. doi:10.4274/jcrpe.galenos.2022.2021-9-19
Lanciotti L, Cofini M, Leonardi A, Penta L, Esposito S.Up-to-date review about minipuberty and overview on hypothalamic-pituitary-gonadal axis activation in fetal and neonatal life.Front Endocrinol (Lausanne).2018;9:410. doi:10.3389/fendo.2018.00410
Khan L.Puberty: onset and progression.Pediatr Ann. 2019;48(4):e141-e145. doi:10.3928/19382359-20190322-01
MedlinePlus.Kallmann syndrome.
Genetic and Rare Diseases Information Center.Congenital adrenal hyperplasia (CAH).
Gunasekaran K, Khan SD.Micropenis. In:Sexual Medicine: Principles and Practice. New York, NY: Springer; 2019:113-20.
Salvi NB, Ghassabian A, Brubaker SG, et al.Prenatal phthalate exposure and fetal penile length and width.Pediatr Res.2024 May;95(6):1587–1595. doi:10.1038/s41390-023-02939-x
Bustamante-Monte LP, Hernandez-Valero MA, Flores-Pimental D. et al.Prenatal exposure to phthalates is associated with decreased anogenital distance and penile size in male newborns.J Dev Orig Health Dis. 2013 Aug;4(4):10.1017/S2040174413000172. doi:10.1017/S2040174413000172
Matsuzaki T, Munkhzaya M, Tungalgsuvd A, et al.Prenatal undernutrition disrupted the sexual maturation, but not the sexual behavior, in male rats.Reprod Med Biol. 2017 Oct;16(4):325–329. doi:10.1002/rmb2.12045
Soliman A, De Sanctis V, Elalaily R.Nutrition and pubertal development.Indian J Endocrinol Metab.2014 Nov;18(Suppl 1):S39–S47. doi:10.4103/2230-8210.145073
Chin HB, Kelly A, Adgent MA.Reproductive hormone concentrations and associated anatomical responses: does soy formula affect minipuberty in boys?J Clin Endocrinol Metab. 2021 Aug 18;106(9):2635-45. doi:10.1210/clinem/dgab354
Cohen PR.Adult acquired buried penis: a hidden problem in obese men.Cureus.2021 Feb;13(2):e13067. doi:10.7759/cureus.13067
Belladelli F, Giudice FD, Glover F, et al.Worldwide temporal trends in penile length: a systematic review and meta-analysis.World J Mens Health. 2023. doi:10.5534/wjmh.220203
Alves Barboza R, Da Silva EA, Ruellas T, Damião R.Anthropometric study of penile length in self-declared Brazilians regarding the color of the skin as White or Black: the study of a myth.Int J Impot Res. 2018;30(1):43-7. doi:10.1038/s41443-017-0009-z
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