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.