Patient's question:
What size is normal for a penis?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: One is to measure in a flaccid state, and the other is to measure the change during an erect state. The measurement should be done in a room with a temperature of around 25°C after calming down and resting appropriately. The penis should be held flat with one end of a ruler slightly 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 external urethral orifice 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 male youth and the erect length of 126 healthy males. 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 males, finding 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, with 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 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 in a normal state is not constant; it can shorten under stress, cold, or severe fatigue. Moreover, the methods of measurement themselves differ significantly, making it difficult to judge whether a penis is normal solely based on length. Therefore, these numbers 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 performed 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 and no erectile function, especially poor development of 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 the primary site of the lesion, with normal hypothalamus and pituitary that can issue strong commands but the testes are diseased and unable to execute the command to produce hormones and sperm.
(2) Hypogonadism due to low gonadotropin, where the hypothalamus and pituitary are affected and cannot issue commands to secrete testosterone. 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, and even possible hypospadias.
(4) Idiopathic micropenis, with the cause or etiology still unknown.
To further explain the factors or causes of a large or small penis, let us 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. The testosterone produced by hCG secreted by the placenta is the active factor at this stage.
(2) Mid to late pregnancy (6 months), when the penis grows rapidly, reaching 2.5-3.5 cm at birth. The fetal pituitary begins to secrete LH and FSH.
(3) From birth to pre-puberty (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 hormone secretion is, and the penis grows rapidly, reaching adult size and thickness in about 5 years. With a significant decrease in sex hormone levels in old age or after surgical castration, the penis may undergo secondary atrophy. If secondary erectile dysfunction stops sexual contact for many years, it may also lead to pathological atrophy, which is not the usual 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, the penis develops at a slower rate, and the penis will be smaller at birth.