Age-specific Contributions to Height in Boys with Klinefelter Syndrome: Analysis of Growth Using the QEPS Model.

CONTEXT: Increased height is a characteristic of Klinefelter syndrome (KS). Detailed evaluation of growth patterns in boys and adolescents carrying a 47,XXY karyotype is lacking.

OBJECTIVE

To delineate detailed growth patterns during the different growth phases and their contribution to the increased adult height in boys with KS.

METHODS

Longitudinal data on growth from 55 boys with KS were compared with a reference from the GrowUp1974Gothenburg cohort using a statistical growth model using 4 mathematical functions: the QEPS model. A subgroup of 35 boys out of whom 34 were on testosterone replacement therapy (TRT) reached final height.

RESULTS

The infant growth period was shorter with a lower height gain (Emax, 63.3 vs 65.1 cm, P < .001) in boys with KS. The boys gained more height during the childhood growth phase, (Qmax, 110.9 vs 104.1 cm, P < .001), and onset of pubertal growth was earlier as compared with the reference (11.3 vs 11.8 years, P < .001). The total pubertal height gain was higher (32.9 vs 30.6 cm, P < .001) due to more basic growth; the specific pubertal growth was equal, resulting in a taller adult height (184.6 vs 180.5 cm, P < .001).

CONCLUSION

The boys with KS exhibited a different growth pattern as compared with a healthy reference population, with less and shorter growth in infant life and more basic growth during childhood and the pubertal years (the Q-function growth by the QEPS model), resulting in taller adult height.