Is a small penis a disease?

Patient's question:

I am a 23-year-old young man. When I was 16-17, during the normal sexual development of men, I accidentally learned what is now referred to as "masturbation." At that time, I didn't know anything about it, so I didn't touch my sexual organs with my hands; instead, I just made my sexual organs move intensely and then let them ejaculate. Afterwards, I only knew it felt good and had no other thoughts. But as time went by, the frequency of my actions increased. It wasn't until a few years later that I learned about sexual knowledge and, after comparing with friends, realized the severity of the situation. Now my sexual organs are very small, and when erect, they are less than 10 centimeters. Masturbation time

Doctor's answer:

How is a penis considered too small?
A young woman told the doctor that her husband's penis was particularly short, even when erect, and that she had never experienced any pleasure during sexual activity. Therefore, she specifically came to ask the doctor whether her husband's penis was normal.
Most young men are curious and often secretly compare the size of their penises in places like public baths. Once they realize their penis is smaller than others', they may develop a sense of inferiority, shame, and frustration, to the point where they no longer want to go to public baths or swimming pools. Is the problem really that serious?
To answer such questions, it's first necessary to clarify what constitutes an abnormal penis. Next, one must determine whether the issue is abnormal development or simply individual variation within the normal range. Finally, and most importantly, if the penis is slightly smaller, will it affect normal sexual activity? In other words, can it provide pleasure to the partner?
The penis, like height, weight, and facial features, varies greatly in size, length, and circumference. Shi Chengli of China measured the penis sizes of 1,412 healthy young Chinese men and the erect lengths of 126 healthy men. The results showed that in a normal state, the longest penis was 14.5 cm, the shortest 4 cm, with an average of 8.375 cm. The circumference ranged from a maximum of 12 cm to a minimum of 4.5 cm, with an average of 8.3 cm. When erect, the longest penis was 16 cm, the shortest 9 cm, with an average of 12 cm. The circumference during erection ranged from a maximum of 14 cm to a minimum of 8 cm, with an average of 10.75 cm. Liu Guozhen et al. surveyed 1,000 normal adult men and found that the penis length in a non-erect state ranged from 4.9 to 8.6 cm, with an average of 6.55 cm, the longest being 10.6 cm and the shortest 3.7 cm. Wu Weicheng et al. measured the penises of 2,547 male college students aged 16–40 and found an average length of 7.43 cm and an average circumference of 8.17 cm. The average penile stretch was 13.34 cm, similar to the calculated erect length of 13.08 cm, suggesting that penile stretch can represent the length after erection. It is clear that different authors' measurements vary, and the results are also influenced by region and ethnicity. Additionally, a person's penis length in a normal state is not constant; it can shorten under stress, cold, or severe fatigue. Moreover, measurement methods differ significantly, making it difficult to judge normality solely based on length. Therefore, these numbers are only for reference and should not be used to rigidly compare one's own length. Clinicians also prefer not to judge normality based on penis size. As long as sexual intercourse is normal and the ability to reproduce is maintained, the penis is considered normal. Otherwise, this family line would have been eliminated long ago.
To further explain the factors or causes of a larger or smaller penis, let's revisit the development process of the penis. For convenience, we can divide it into four stages:
(1) Weeks 10–12 of pregnancy: The penis has just differentiated and is only 3.5 mm long. At this stage, the hormone hCG secreted by the placenta stimulates testosterone production.
(2) Mid-to-late pregnancy (6 months): The penis grows rapidly, reaching 2.5–3.5 cm at birth. At this time, the fetal pituitary begins to secrete gonadotropin hormones LH and FSH.
(3) From birth to before puberty (around age 7): Penis growth is slow due to the slower development of the hypothalamus and pituitary, as well as low testosterone levels.
(4) After puberty begins, the pituitary and testes secrete hormones in abundance, and the penis grows rapidly, reaching adult size in about 5 years, increasing in both length and girth. When elderly hormone levels significantly decrease or after surgical castration, the penis may undergo secondary atrophy. If secondary erectile dysfunction persists for many years without sexual activity, pathological atrophy may also occur. This is not the usual "use it or lose it" phenomenon but rather the result of degenerative changes in smooth muscle fibers.
In summary, the differentiation and development of the penis rely entirely on testosterone levels in the body. If testosterone secretion is insufficient during weeks 6–9 of pregnancy, the penis will develop more slowly, resulting in a smaller penis at birth.
So, how is a truly small penis defined? If the penis is shorter than 2.5 cm before puberty and shorter than 5 cm after puberty, and if it is underdeveloped, lacks erection function, and exhibits poor secondary sexual characteristics, sexual dysfunction, infertility, and no sperm, then it can be considered abnormally developed. The causes of true micropenis include:
(1) Hypogonadism with high gonadotropin levels originating in the testes. In this case, the hypothalamus and pituitary are normal and can issue strong commands, but the testes are diseased and cannot execute the commands to produce hormones and sperm.
(2) Hypogonadism with low gonadotropin levels, where the hypothalamus and pituitary are damaged and cannot issue instructions to secrete testosterone. These two conditions have been described in the book (page 232).
(3) Partial androgen insensitivity syndrome, where the penis is insensitive to androgens. The patient's testosterone levels are normal, but their secondary sexual characteristics are abnormal, and they may even have hypospadias.
(4) Idiopathic micropenis, where the cause or reason remains unknown.
Let's return to the woman mentioned earlier. Since she became pregnant about 9 months after marriage and gave birth to a healthy son, it indicates that her husband's sexual function is normal and that there are no endocrine issues. His penis clearly falls within the normal range. Such normal physiological differences need not cause concern. As for female sexual satisfaction and mutual sexual harmony, these are primarily due to a lack of sexual knowledge and techniques, not the size of the penis. By the way, the method of measuring penis length is important: first, measure in a flaccid state, and then measure the change during erection. The room temperature should be around 25°C, and the person should be calm and rested before measuring. The penis should be held flat, and one end of a ruler should be pressed firmly against the pubic symphysis, compressing the subcutaneous fat layer as much as possible. The other end should be aligned with the urethral meatus of the glans to read the normal flaccid length. A tape measure can then be used to measure the circumference of the penis shaft, 1 cm away from the corona. Since patients may become tense or uncomfortable in the clinic, they often cannot achieve full erection, so the stretched length of the penis is often used as a substitute for the erect length.
Additionally, the testicles should not be as big as eggs.