ESPE Abstracts

Background: Klinefelter syndrome (KS) is associated with an increased metabolic and cardiovascular risk profile^1,2 and a metabolic syndrome is evident at a prepubertal age in 10% of the affected boys. Boys with KS tend to avoid competitive sports and describe themselves as ‘not good at sports’. Cardiopulmonary fitness in adults with KS has been found to be compromised by chronotropic insufficiency (CI) and a reduced maximal oxygen uptake (V'O2max; ml/min) as a parameter of aerobic cardiorespiratory fitness.² We aimed to investigate cardiopulmonary fitness in boys and adolescents with KS as part of the KliBone study.

Methods: Boys and adolescents (6 – 25 years) with KS were included in the KliBone study (DRKS 00024870). Body composition was measured using a Tanita impedance scale. Hand grip strength (HGS) was measured using a Jamar handgrip dynamometer. Participants underwent an incremental symptom-limited cardiopulmonary exercise test (CPET) on a bicycle ergometer according to the recommended protocol. Individual z-scores for participants were calculated based on the age-appropriate normative data. Age-predicted maximal heart rate was calculated, and CI was defined according to Pasquali et al.²

Results: Nineteen participants with KS (five on testosterone replacement therapy) aged 15.90 ± 4.12 (range 9 – 25) years with a BMI z-score of 0.47 ± 1.22, (range -2.00 – 1.90) participated in the study. Mean adipose mass (%) was 23.36 ± 9.00. 17 participants underwent CPET. Mean z-scores were -2.48 ± 2.13 (range -7.97 – 0.41) for HRmax; -1.29 ± 1.37 (range -3.04 – 1.77) for Wattmax and -2.28 ± 2.48 (range -6.88 – 0.57) for V'O2max. Seven participants (41.2%) met the criteria for CI. These participants reached significantly reduced Wattmax (134.14 ± 29.70 vs. 182.20 ± 52.42; P=0.04) and tended to a reduced V'O2max(1789.29 ± 568.32 vs. 2280.30 ± 652.84; P=0.08) when compared to KS participants without CI. Mean HGS z-score was 0.97 ± 1.37 without differences between participants with or without CI.

Conclusion: Cardiopulmonary impairment has been reported in adult men with KS. Here we show that impaired cardiopulmonary fitness can be detected already in boys and adolescents with KS and in 40% of the participants CI was detected. The presence of CI is associated with further reduction of cardiopulmonary performance. Further research needs to focus on this important aspect of KS, that may explain the avoidance of competitive sports in KS and may contribute to the unfavorable metabolic phenotype.

1. Salzano et al. Klinefelter syndrome, cardiovascular system, and thromboembolic disease

2. Pasquali et al. Cardiovascular abnormalities in Klinefelter syndrome.