Levels of evidence (1a-4) and grades of recommendation (A-C) are defined at the end of the "Major Recommendations" field.
Background
Micropenis is a small but otherwise normally formed penis with a stretched length of less than 2.5 standard deviations (SD) below the mean.
Besides an idiopathic micropenis, two major causes of abnormal hormonal stimulation have been identified:
- Hypogonadotropic hypogonadism (due to an inadequate secretion of gonadotrophin-releasing hormone [GnRH])
- Hypergonadotropic hypogonadism (due to failure of the testes to produce testosterone).
Diagnosis
The penis is measured on the dorsal aspect, while stretching the penis, from the pubic symphysis to the tip of the glans. The corpora cavernosa are palpated, the scrotum is often small, and the testes may be small and descended. Micropenis should be distinguished from buried and webbed penis, which is usually of normal size.
The initial evaluation has to define whether the aetiology of the micropenis is central (hypothalamic/pituitary) or testicular. A paediatric endocrinology work-up has to be carried out immediately. Karyotyping is mandatory in all patients with a micropenis.
Endocrine testicular function is assessed (baseline and stimulated testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) serum levels. Stimulated hormone levels may also give an idea of the growth potential of the penis. In patients with non-palpable testes and hypogonadotropic hypogonadism, laparoscopy should be carried out to confirm vanishing testes syndrome or intra-abdominal undescended hypoplastic testes. This investigation can be delayed until the age of 1 year.
Treatment
Pituitary or testicular insufficiency is treated by the paediatric endocrinologist. In patients with testicular failure and proven androgen sensitivity, androgen therapy is recommended during childhood and at puberty to stimulate the growth of the penis (Level of evidence: 2; Grade of recommendation: B). In the presence of androgen insensitivity, good outcome of sexual function is questioned and gender conversion can be considered.
Definitions:
Levels of Evidence
1a Evidence obtained from meta-analysis of randomized trials
1b Evidence obtained from at least one randomized trial
2a Evidence obtained from at least one well-designed controlled study without randomization
2b Evidence obtained from at least one other type of well-designed quasi-experimental study
3 Evidence obtained from well-designed non-experimental studies, such as comparative studies, correlation studies and case reports
4 Evidence obtained from expert committee reports or opinions or clinical experience of respected authorities
Grades of Recommendation
- Based on clinical studies of good quality and consistency addressing the specific recommendations and including at least one randomized trial
- Based on well-conducted clinical studies, but without randomized clinical studies
- Made despite the absence of directly applicable clinical studies of good quality
