Patient's question:
I've always wondered what size a man's penis should be, and why there are so many advertisements for aphrodisiacs. Are they trustworthy?Doctor's answer:
What is the standard size of the penis?How can a penis be considered abnormal? If the penis is slightly smaller, will it affect normal sexual life? In other words, can it provide pleasure to the wife?
Methods for measuring penis length:
1. Measure in a flaccid state, and 2. Measure the change during an erect state. The measurement should be done at a room temperature of around 25°C after calming down and resting appropriately. Gently hold the penis flat with one end of a ruler firmly pressed against the pubic symphysis, compressing the subcutaneous fat layer as much as possible. The other end of the ruler should be aligned with the urethral meatus of the glans penis, and the reading obtained is the normal length of the penis. Then, use a tape measure to measure the circumference of the penile shaft, 1 cm away from the corona.
The penis, like height, weight, and facial features, varies greatly among individuals, with differences in length and thickness. Shi Chengli measured the penis size of 1,412 healthy Chinese young men and the erect length of 126 healthy men. The results showed that the longest normal length was 14.5 cm, the shortest 4 cm, and the average 8.375 cm. The maximum circumference was 12 cm, the minimum 4.5 cm, and the average 8.3 cm. During erection, the longest was 16 cm, the shortest 9 cm, and the average 12 cm. The maximum erect circumference was 14 cm, the minimum 8 cm, and the average 10.75 cm. Liu Guozhen et al. surveyed 1,000 normal adult men and found that the normal length 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 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 erect length. It is evident that different authors' measurements vary, and the results are also influenced by region and ethnicity. Additionally, a person's penis length is not constant under normal conditions; it may shorten during tension, cold, or severe fatigue. Moreover, measurement methods themselves differ significantly, making it difficult to judge whether a penis is normal solely based on length. Therefore, these figures are only for reference and should not be rigidly compared to one's own length. Clinicians are also reluctant to judge normality based on penis length. As long as normal sexual intercourse can be achieved and the ability to reproduce is maintained, it is considered normal. Otherwise, this family line would have been eliminated long ago.
So, what constitutes a truly small penis? A penis shorter than 2.5 cm before puberty and shorter than 5 cm after puberty, with abnormal development, no erection function, poor secondary sexual characteristics, sexual dysfunction, infertility, and no sperm can be considered abnormally developed. The causes of true micropenis include:
(1) High gonadotropin-dependent hypogonadism where the testes are diseased but the hypothalamus and pituitary are normal, unable to execute the command to produce hormones and sperm.
(2) Hypogonadism due to low gonadotropin, where the hypothalamus and pituitary are diseased, unable to issue testosterone secretion commands. These two conditions have been described separately in this book.
(3) Partial androgen insensitivity syndrome, where the penis is insensitive to androgens, with normal testosterone levels but abnormal secondary sexual characteristics, possibly even hypospadias.
(4) Idiopathic micropenis, with unknown causes or etiology.
To further explain the factors or causes of a large or small penis, let's revisit the process of penis development. For convenience, we divide it into four stages:
(1) Weeks 10-12 of pregnancy, when the penis has just differentiated and is only 3.5 mm long, with testosterone produced by hCG secreted by the placenta.
(2) Mid to late pregnancy (6 months), when the penis grows rapidly, reaching 2.5-3.5 cm at birth, with the fetal pituitary beginning to secrete LH and FSH.
(3) From birth to prepuberty (around 7 years old), penis growth is slow due to the slow development of the hypothalamus and pituitary and low testosterone levels.
(4) After puberty, the pituitary and testicular hormones are secreted vigorously, and the penis grows rapidly, reaching adult size and thickness in about 5 years. With significant decreases in sex hormone levels in old age or after surgical castration, the penis may undergo secondary atrophy. If secondary erectile dysfunction persists for many years without sexual contact, it may lead to pathological atrophy, which is not the general issue of "use it or lose it" but rather the result of degenerative changes in smooth muscle fibers.
In summary, the differentiation and development of the penis rely entirely on the testosterone level in the body. If testosterone secretion is insufficient during weeks 6-9 of pregnancy, penis development will be slower than normal, and the penis will be smaller at birth.