Gynaecomastia results from an imbalance in hormone levels in which levels of oestrogen are increased relative to levels of androgens. When the condition occurs in normally growing infant and pubertal boys, that resolves on its own with time, is known as physiological gynaecomastia.
All individuals, whether male or female, possess both female hormones and male hormones. During puberty, levels of these hormones may fluctuate and rise at different levels, resulting in a temporary state in which oestrogen concentration is relatively high. Studies regarding the prevalence of gynaecomastia in normal adolescents have yielded widely varying results, with prevalence estimates as low as 4% and as high as 69% of adolescent boys. These differences probably result from variations in what is perceived to be normal and the different ages of boys examined in the studies.
Gynaecomastia caused by transient changes in hormone levels with growth usually disappears on its own within six months to two years. Occasionally, the condition can develop in puberty and persist beyond two years. This is referred to as persistent pubertal gynaecomastia.
A number of medical conditions may also result in gynaecomastia:
- Malnutrition and re-feeding have both been shown to create a hormonal environment that may lead to the condition. Similarly, cirrhosis of the liver alters normal hormone metabolism and may also lead to this.
- Disorders of the male sex organs can result in decreased testosterone production and relatively high oestrogen levels, leading to gynaecomastia. These disorders may be genetic, such as Klinefelter’s syndrome or acquired due to trauma, infection, reduced blood flow, or ageing. Testicular cancers may also secrete hormones that cause this.
- Other conditions that are associated with an altered hormonal environment in the body and may be associated, are chronic renal failure and hyperthyroidism. Rarely, cancers other than testicular tumours may produce hormones that can cause gynaecomastia.