Testosterone and leptin in older African-American men: relationship to age, strength, function, and season

Testosterone (T) and bioavailable testosterone (BT) levels have been shown to decline with aging in Caucasian males. We are unaware of any studies that have examined this in African-American men. Previous studies have suggested a relationship of T to strength and leptin levels, but no such correlation with measured functional tests exists. This study explores these associations in a cross-sectional sample of older African-Americans from the Saint Louis University Inner City Aging Project. The participants were 65 African-American males aged 70 to 102 years. Measurements included T, BT, and leptin levels, isometric muscle strength, and relevant physical impairments. Statistical analysis included a t test and simple and multiple ordinary least-squares regression. Age was inversely related to T and BT. Of these older African-American males, 90.7% had a BT value less than the normal range for young males. T correlated with upper- and lower-limb strength and functional tests. Leptin was correlated with the body mass index (BMI) and inversely with T, but not with BT. Circannual rhythms for T, BT, and leptin were present. This study demonstrates for the first time an age-related decrease in T and BT in African-Americans and a circannual rhythm for leptin. T was correlated with upper- and lower-limb strength and functional status.