Comparison of the mean serum TGF-1β concentration (ng/ml) in baboons by gender and age group (<9 yrs, n = 31 females, 12 males; 9-17 yrs, n = 34 females, 6 males; >17 yrs, n = 31 females, 4 males). Different lower case letters represent differences between female age groups and different upper case letters represent differences between male age groups. Due to the lower number of males in each age group, a comparison of the mean levels of serum TGF-1β between females and males within the same age group was not included. Data are expressed as means ± SEM. Means with no common letters differ significantly, P ≤ 0.05.