Title of the manuscript: Chylothorax in a 4-year-old boy with trisomy 21

Background: Low endogenous testosterone has been associated with increased cardiovascular risk in men.

Objectives: To determine the prevalence of low serum testosterone level (TT) in a cohort of male US career firefighters and to examine its relation with left ventricular wall thickness (LVWT).

Material and methods: We conducted a cross-sectional study among 341 career firefighters, (age:37.5±10.3 years; BMI:28.9±4.5 kg/m² ), who underwent an occupational medical screening examination. TT quartiles were determined and LVWT distribution among them were plotted. Then, TT values were categorized as low (<264 ng/dL), borderline (264-399 ng/dL), reference range (400-916 ng/dL) and high (>916 ng/dL). To further investigate the association of mildly decreased TT on LVWT, we divided the borderline group into borderline-low (264-319 ng/dL) and borderline-high (320-399 ng/dL) ranges. LVWT values were classified as low-LVWT when <0.6 cm. A multivariate model was used to compare LVWT, age, BMI, systolic blood pressure (SBP) and HbA1c among groups by TT values.

Results: The prevalence of low TT was 10.6%, and borderline was 26.4%, while 58.7% had levels in the reference range. The low-TT group was older, had higher BMI and SBP as compared to the reference group (p<0.01). LVWT values were different among groups (p=0.04) and significantly lower in firefighters with borderline-low TT as compared to the reference group (p<0.05). This finding also occurred within obese firefighters (p=0.03). The borderline-low group had a higher adjusted risk for a low-LVWT as compared to the reference group [OR:4.11(95%CI:1.79-9.43)].

Discussion: Our findings highlight the possible relationship between a mild reduction in testosterone levels (borderline) and lower LVWT.

Conclusions: A high prevalence of subnormal TT levels (low and borderline: 37%) was observed in this relatively homogeneous cohort of career firefighters. Mildly decreased TT levels and lower LVWT might represent a preclinical condition and a window of opportunity for cardiovascular preventive interventions in firefighters.

Keywords: Testosterone; cardiac structure; cardiovascular risk; firefighter; heart; left ventricular; preclinical testosterone deficiency.