| disease | Small Penis |
Microphallus is a relatively common congenital anomaly, characterized by a penis length that is 2 standard deviations (cm) smaller than that of peers, and is referred to as microphallus.
bubble_chart Etiology
Disease cause: Micropenis is associated with testosterone deficiency in the body, which results from underdevelopment of hormone target organs. It is often accompanied by poor testicular development and incomplete descent. Additionally, the development of other organs (including the scrotum) may also be affected. There is a reduction in luteinizing hormone-releasing hormone (LHRH) secreted by the hypothalamus. Since the pituitary-gonadal axis is unaffected, testosterone treatment can still have some effect, though it may be weak. For example, topical application of 5% testosterone cream can help increase penile size by facilitating local hormone absorption, which subsequently promotes the development of the reproductive system systemically.
bubble_chart Clinical Manifestations
The external genitalia, especially the penis, may be smaller, with no scrotum or undetectable testes, and the prostate is also notably small. (Appendix 1)
Table 1 Length of the Flaccid Penis and Testicular Size from Infancy to Adulthood
| Age (years) | Penis Length (cm±SD) | Testicular Diameter (cm±SD) |
| 0.2～2 | 2.7±0.5 | 1.4±0.4 |
| 2.1～4 | 3.3±0.4 | 1.2±0.4 |
| 4.1～6 | 3.9±0.9 | 1.5±0.6 |
| 6.1～8 | 4.2±0.8 | 1.8±0.3 |
| 8.1～10 | 4.9±1 | 2±0.5 |
| 10.1～12 | 5.2±1.3 | 2.7±0.7 |
| 12.1～14 | 6.2±2 | 3.4±0.8 |
| 14.1～16 | 8.6±2.4 | 4.1±1 |
| 16.1～18 | 9.9±1.7 | 5±0.5 |
| 18.1～20 | 11±1.1 | 5±0.3 |
| 20.1～25 | 12.4±1.6 | 5.2±0.6 |
bubble_chart Treatment Measures
In recent years, there have been some improvements in the treatment of micropenis. However, androgen replacement remains the primary treatment method. By providing sufficient testosterone to the patient's body, it stimulates penile development without affecting bone growth and closure. The treatment recommended by Aller involves administering 25mg of oral testosterone every three weeks, with a total dose not exceeding 100mg. The effectiveness of the treatment should be evaluated by measuring the penile length (from the pubis to the glans) before and after treatment. Treatment should begin at the age of one. The goal is to ensure that the child's genital development keeps pace with overall body growth. If the child's penile growth is significantly slower than that of peers, the above treatment should be repeated. For children with cryptorchidism, orchiopexy should be performed before the age of two. LHRH can also be used to promote penile development and testicular descent.
Microphallus should be distinguished from concealed penis. Other endocrine and central nervous system abnormalities should be ruled out. Delayed bone growth, anosmia, learning disabilities, deficiencies in adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH) are all associated with microphallus. Sexual function should also be thoroughly assessed.