Growth Hormone and Weight Gain in African-American Girls

Researchers have long sought to explain why African-American girls are more sexually mature, taller and heavier, with more muscle mass and body fat than their Caucasian peers. One clue may lie in higher-than-normal levels of a growth hormone (J Pediatrics 1999; 135:296).

Researchers at Baylor College of Medicine, Houston, found higher blood levels of a potent growth hormone, free IGF-1, in African-American girls than in their Caucasian peers. The study examined hormonal levels of 136 healthy African-American and Caucasian girls of normal weight between the ages of 9 and 17. The results raised the question of whether higher levels of free IGF-1 may be accelerating growth in African-American girls, and whether the higher levels might be a factor in excessive weight gain if the hormone levels remain high once an individual’s growth is complete.

Insulin may also be involved in the degree of free IGF-1 in circulation in the body Insulin inhibits production of one of the binding proteins that inactivate IGF-1. According to the authors, this connection is significant because healthy, normal-weight African-American children have higher blood insulin levels than Caucasians. High insulin is though to predispose people to adult-onset, or Type 2, diabetes. Even when diabetes doesn’t develop, higher than normal insulin levels might contribute to high cholesterol, weight problems, and hypertension. All of these problems are more prevalent among African-Americans.