Testosterone Effects on Short-Term Physical, Hormonal, and Neurodevelopmental Outcomes in Infants with 47,XXY/Klinefelter Syndrome: The TESTO Randomized Controlled Trial

Abstract

Context: 47,XXY/Klinefelter syndrome (XXY) is associated with impaired testicular function and differences in physical growth, metabolism, and neurodevelopment. Clinical features of XXY may be attributable to inadequate testosterone during the mini-puberty period of infancy.

Objective: We tested the hypothesis that exogenous testosterone treatment positively effects short-term physical, hormonal, and neurodevelopmental outcomes in infants with XXY.

Design: Double-blind randomized controlled trial, 2017-2021.

Setting: US tertiary care pediatric hospital.

Patients: Infants 30-90 days of age with prenatally identified, non-mosaic 47,XXY (n=71).

Intervention: Testosterone cypionate 25mg intramuscular injections every 4 weeks for 3 doses.

Main outcome measures: The a priori primary outcomes were change in percent fat mass (%FM) z-scores and change in the total composite percentile on Alberta Infant Motor Scales (AIMS) assessment from baseline to 12 weeks.

Results: The between group difference in change in %FM z-scores was -0.57 [95% CI -1.1, -0.06], p=0.03), secondary to greater increases in lean mass in the testosterone-treated group (1.5±0.4 kg vs 1.2±0.4, p=0.001). Testosterone suppressed gonadotropins and inhibin B (p<0.001 for all). In contrast, there were no significant group differences in short term motor, cognitive, or language outcomes (p>0.15 for all).

Conclusions: In this double-blind randomized controlled trial in infants with XXY, testosterone injections resulted in physical effects attributable to systemic androgen exposure; however, there was no impact on neurodevelopmental outcomes and the hypothalamic-pituitary-gonadal axis was suppressed. These results do not support routine testosterone treatment in infants with XXY, however long term follow up on physical health, neurodevelopment and testicular function is needed.

Keywords: Klinefelter syndrome; critical window; mini puberty period; testosterone.

Figure 1.

CONSORT diagram detailing participant allocation and completion of primary outcome measures for the TESTO trial.

FIGURE 2.

Mean and 95% confidence interval of the mean by study visit for Group A (blue line; testosterone first, placebo second) and Group B (orange dashed line, placebo first, testosterone second) at Visit 1 (baseline, ~2 months of age), Visit 2 (~5 months of age), and Visit 3 (~8 months of age). Outcomes from blinded physical examination (row 1), PEAPOD air displacement plethysmography (row 2), neurodevelopmental assessment (row 3), and parent-reported development (row 4). Where applicable, dashed line represents the average in the general population and normal ranges are depicted with a shaded background. Significant differences between groups is indicated by asterices (* = <0.05, ** = <0.01, *** = <0.001). AIMS = Alberta Infant Motor Scales; ABAS = Adaptive Behavior Assessment System Third Edition

Figure 3.

Spaghetti plots for longitudinal hormone concentrations by age (1–9 months) and corresponding box plots at each study visit for those in group A (blue) treated with testosterone followed by placebo, and group B (orange) treated with placebo followed by testosterone. Each circle is a value for an individual participant at a given time; lines of the spaghetti plot represent individual participants over time, and the bolder lines are smoothed loess curves with 95% confidence intervals around the loess curves for each group. Box plots show the 1^st and 3^rd quartiles as the bottom and top of the box respectively with median in the middle and error bars representing 95% of the data. LH = luteinizing hormone, FSH = follicle stimulating hormone, AMH = anti-mullerian hormone.