Are Klinefelter boys hypogonadal?

Area of Science:

• Endocrinology
• Reproductive Biology
• Genetics

Background:

• Male hypogonadism involves decreased function of testicular germ, Leydig, or Sertoli cells.
• Klinefelter syndrome is the most common cause of adult male hypogonadism.
• Early gonadal function in boys with Klinefelter syndrome is debated.

Purpose of the Study:

• To review the onset and progression of gonadal dysfunction in Klinefelter syndrome during infancy and childhood.
• To analyze the impact on germ, Leydig, and Sertoli cell function.
• To clarify controversial findings regarding Leydig cell function in affected boys.

Main Methods:

• Literature review of studies on testicular cell function in Klinefelter syndrome.
• Analysis of data on anti-Müllerian hormone (AMH), inhibin B, and testosterone levels.
• Comparison of findings across different age groups from fetal life through puberty.

Main Results:

• Germ cell degeneration begins in fetal life, leading to reduced numbers at birth and significant depletion during puberty.
• Leydig cell testosterone production shows controversial results, reported as normal to low or normal to high in infancy and childhood.
• Sertoli cell function, indicated by normal AMH and inhibin B in prepubertal boys, declines only in mid- to late puberty.

Conclusions:

• Klinefelter syndrome is a primary hypogonadism impacting all testicular cell types.
• Germ cells are affected early, with severe depletion occurring at puberty.
• Leydig cells may be normal or mildly affected early on, and Sertoli cells remain functional until later puberty.