Relationship between age, BMI, and hormones

The cohort was stratified according to BMI into three groups: nonobese (BMI <25 kg/m²), overweight (BMI ≥25 to <30 kg/m²), and obese (BMI ≥30 kg/m²). Mean (95% CI in shaded area and vertical lines) total and free testosterone and SHBG were significantly lower in the overweight and obese at all ages, compared with nonobese. The total testosterone and SHBG age trends in the three BMI categories were similar (indicating no interaction between BMI and age); the free testosterone age trend in the obese group was less steep than in the other two groups (indicating an interaction between BMI and age). Mean LH was not significantly different among the three groups at the median age of 60 years. LH was higher in the older than 70 years nonobese, compared with the overweight and obese groups, due to a negative BMI/age interaction.