Cardiorespiratory fitness in adolescents and young adults with Klinefelter syndrome - a pilot study

Abstract

Background: Klinefelter syndrome (KS) may be associated with a wide spectrum of phenotypic changes including endocrine, metabolic, cognitive, psychiatric and cardiorespiratory pathologies in adults. However, in adolescence the clinical phenotype of KS is not well described, especially regarding physical fitness. The present study reports on cardiorespiratory function in adolescents and young adults with KS.

Methods: Adolescents and young adults with KS were recruited in a cross-sectional pilot study. Biochemical parameters of fitness including hormonal status, a body impedance analysis, the grip strength, the amount of physical activity at home for 5 days via trackbands and anamnestic parameters were assessed. In addition, participants underwent an incremental symptom-limited cardiopulmonary exercise test (CPET) on a bicycle ergometer.

Results: Nineteen participants with KS aged 15.90 ± 4.12 years (range: 9.00 - 25.00) participated in the study. Pubertal status was Tanner 1 (n = 2), Tanner 2 - 4 (n = 7) and Tanner 5 (n = 10). Seven participants received testosterone replacement therapy. Mean BMI z-score was 0.45 ± 1.36 and mean fat mass was 22.93% ± 9.09. Grip strength was age-appropriate or above normal. 18 participants underwent CPET with subnormal results for maximum heart rate (z-score -2.84 ± 2.04); maximum workload (Watt_max; z score -1.28 ± 1.15) and maximum oxygen uptake per minute (z- score -2.25 ± 2.46). Eight participants (42.1%) met the criteria for chronotropic insufficiency (CI). Data from track-bands showed sedentary behavior for 81.15% ± 6.72 of the wear time.

Conclusion: A substantial impairment of cardiopulmonary function can be detected in this group of boys to young adults with KS, including chronotropic insufficiency in 40%. The track-band data suggest a predominantly sedentary lifestyle, despite normal muscular strength as assessed via grip strength. Future studies need to investigate the cardiorespiratory system and its adaption to physical stress in a larger cohort and in more detail. It is feasible that the observed impairments contribute to the avoidance of sports in individuals with KS and may contribute to the development of obesity and the unfavorable metabolic phenotype.

Keywords: Klinefelter syndrome; XXY; adolescence; cardiovascular disease; children; chronotropic insufficiency; physical activity.

Figure 1

Hand grip strength. Results of hand grip strength measurement in participants with KS (red squares and green circles) and age-appropriate percentiles according to Dodds et al. (21) Presence of chronotropic insufficiency (CI) in participants is indicated by color (red squares = with CI; green circles = without CI).

Figure 2

Cardiopulmonary exercise test (CPET). Results of CPET in participants with KS (red squares and green circles) expressed as (A) maximum workload achieved on the ergometer in Watt, (B) the maximum heart rate in BPM, (C) the maximum oxygen uptake per minute [ml/min] and (D) the respiratory minute volume [l/min]. The grey area indicates the age-appropriate mean and standard deviation according to the results of Klemt et al. (28) for children and adolescents aged 6 to 18 years; the gray patterned area indicates the age-appropriate mean and standard deviation according to the results of Gläser et al. for adults (30). Participants with chronotropic insufficiency (CI) are shown as red squares; participants without chronotropic insufficiency as green circles. HR, Heart rate; V’O2 max, Maximum oxygen uptake; V’E max, Maximum respiratory volume; CI, Chronotropic insufficiency.