Growth during puberty in the XYY boy

Area of Science:

• Genetics
• Pediatrics
• Endocrinology

Background:

• XYY syndrome, a chromosomal condition, affects approximately 1 in 1,000 male births.
• Longitudinal growth studies in XYY individuals identified through newborn screening are limited.
• Understanding growth patterns in XYY syndrome is crucial for clinical management and genetic counseling.

Purpose of the Study:

• To longitudinally assess the growth patterns of XYY boys identified by newborn screening.
• To compare the growth trajectories of XYY boys with a control group from the same population.
• To investigate the influence of the Y chromosome on sexual dimorphism in human growth.

Main Methods:

• A cohort of eight unselected XYY boys was identified via newborn cytogenetic screening.
• Growth parameters, including height and height velocity, were measured longitudinally.
• Comparison was made with age- and population-matched control subjects.

Main Results:

• No significant differences in birth dimensions were observed between XYY boys and controls.
• XYY boys exhibited increased height velocity during childhood, leading to a 7.6 cm height advantage at puberty onset.
• Pubertal growth spurt in XYY boys showed increased intensity (peak height velocity 10.6 cm/year), contributing to an average adult height of 188.1 cm.

Conclusions:

• XYY syndrome is associated with significantly increased adult height compared to the general male population.
• The Y chromosome appears to exert a quantitative effect on growth, amplifying the male-female height difference.
• Newborn screening for XYY syndrome provides a valuable opportunity to study its long-term developmental impact.