Testosterone (T) is one of the male sex hormones called androgens which play a significant role in regulating sexual health.
In fact, T is the main factor stimulating the development of reproductive organs in boys and the formation of a penis even before birth.
The hormone has the most significant effect on penile growth during puberty when the levels of testosterone and other androgens such as dihydrotestosterone (DHT) reach their peak.
Yet, once puberty is complete, penile tissues no longer respond to the growth stimuli by testosterone.
Therefore, administering exogenous testosterone, such as testosterone replacement therapy (TRT), is not effective for increasing penis size if you are an adult man.
Nevertheless, TRT can have multiple benefits if you are suffering from low T and hypogonadism. They include increasing muscle mass, fat loss, libido, mood, energy levels, bone health, and more!
Does testosterone make your penis bigger?
Testosterone promotes penile formation and growth since the 8th week of intrauterine development. That’s the period when its production in the developing testicles begins.
At first, T production is stimulated by the placental human chorionic gonadotropin (hCG), while later, the hypothalamus and the pituitary gland take over by producing the gonadotropins – luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
In addition, the enzyme 5-alpha reductase found in peripheral tissue converts T into the more potent DHT, which also plays a significant role in penile growth. In women, elevated testosterone levels can stimulate the growth of the clitoris and also increase its sensitivity.
After birth and before puberty, both androgen levels and penile growth remain low. Thus, the size of the penis increases only following whole-body development.
Yet, penile growth does not depend only on testosterone and dihydrotestosterone (DHT). The human growth hormone (HGH) also influences the normal development of the reproductive system.
Therefore, children with congenital growth hormone deficiency (GHD) may develop micropenis. Furthermore, HGH therapy has been shown to ameliorate the condition and restore normal penile growth in prepubertal pediatric patients.
After the onset of puberty, androgen levels and penile growth reach their peak, and by the end of this period, the phallus reaches its final length and girth.
Although androgens can no longer stimulate penile growth after puberty, they play a role in normal erectile function in adults.
According to studies, testosterone has a complex effect on erections, and its presence even in extremely low levels is essential for the process.
Can testosterone therapy increase penis size?
Testosterone replacement therapy (TRT) has been shown as highly effective in restoring average size in boys with micropenis as long as the treatment is taken before or during early puberty.
For example, one study has reported that testosterone injections increased the average stretched penile length from 15.54 to 37.18 mm in boys younger than 11 years old.
Research reports that topical and oral TRT is also effective in increasing penis size in children. In fact, studies report that there is no difference when comparing the benefits of topical to injectable testosterone for penile growth.
Yet, scientists warn that even though TRT may help increase penis size in children, the final penile length of many patients treated for micropenis remains lower than average in adulthood.
Starting early treatment is usually the main factor that leads to better results in final penile length. Furthermore, the researchers noted that TRT in childhood might not increase penis size beyond its genetically predetermined length and girth.
Evidence in adults with low T and hypogonadism does not report any benefits of TRT for penis size in adults.
Currently, only one study in hypogonadal adults with micropenis has reported an increase in penis length after 6 months of TRT. However, this trial has a tiny sample size, and results are likely unreliable.
How does low T affect penile growth?
Since T levels and thus penile growth are at their peak during puberty, factors that affect testosterone production can have a negative effect on final penis size.
One such factor is childhood obesity. According to research, obese children have lower testosterone levels and penile growth during puberty. The average penile length was 10% shorter than participants with normal body weight.
Yet, these effects occur only if obesity is present during puberty. Penile growth during the prepubertal period does not appear to be influenced by body weight and body fat levels.
Losing weight before puberty may be an excellent strategy to increase testosterone levels and improve penile growth during this period of rapid growth.
Weight loss will also be beneficial for your testosterone levels during adulthood if you are overweight or obese. Yet, it will not increase penis size in adults, apart from the purely visual effect of reduced prepubic fat on the penis.
Furthermore, if you develop hypogonadism after the end of puberty, your penis size will likely remain unaffected. Therefore, penile atrophy or reduced penis size is not considered a symptom of hypogonadism.
Unfortunately, some forms of hypogonadism, such as those caused by pituitary problems, may affect the size of your testicles instead and lead to testicular atrophy.
Some studies report that extremely low levels of testosterone and DHT, such as those achieved during androgen deprivation therapy for prostate cancer, may lead to penile shrinkage. In one trial, 15 months of androgen deprivation therapy reduced mean stretched penile length from 10.76 cm to 8.05 cm.
What are the causes of micropenis?
Micropenis is a relatively rare congenital condition, which affects about 0.015% of all male newborns in the US.
The condition is defined as stretched penile length in newborns under 0.7 inches (2 cm). In adults, micropenis is considered as stretched penile length under 3.6 inches (9.1 cm).
The possible causes of micropenis include:
- defects in the hypothalamic-pituitary-gonadal axis
- defects in the biosynthesis of T and/or DHT
- defects in androgen and gonadotropin receptors
- isolated growth hormone deficiency
- a primary structural anomaly of the reproductive organs
- genetic mutations and conditions such as Prader-Willi, Klinefelter, and Noonan syndromes
The most common cause is abnormal hypothalamic or pituitary function. In such cases, the penis forms normally thanks to the stimulation of the testicles by maternal hCG. However, the process of penile growth stops after the 14th gestational week.
In addition, conditions such as buried penis and webbed penis can be often mistaken for micropenis.
A buried penis may occur due to obesity, folds of skin, or swelling of the scrotum and the surrounding tissues. Misdiagnosis with micropenis usually occurs in obese prepubertal children, in which the prepubic fat surrounds and “hides” the penis.
In adults, it may also occur due to weak muscles of the pelvic floor. The condition often leads to erectile problems as well.
A webbed penis usually develops after circumcision due to the adhesion of scrotal skin to the shaft’s skin. The condition requires surgery which is generally performed during late childhood.
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