Han YY, Forno E, Witchel SF, et al. - Experts aspired to explore whether a change in free testosterone or free testosterone-to-estradiol ratio is correlated with changes in lung function and eosinophils in the Puerto Rican youth. In a prospective study of 317 children (with and without asthma) followed up from ages 6 to 14 years to ages 10 to 20 years (146 females, 171 males) in San Juan, Puerto Rico, they looked for a link between changes in sex hormone levels and changes in lung function or eosinophils. The increased free testosterone-to-estradiol ratio in Puerto Rican youth was associated with increased FEV ₁/FVC in both genders and increased FEV ₁ in males over time.