GDF11 and coronary artery disorder: It has been recently reported that both the level of GDF11 in the blood and the leukocyte telomere lengths (LTLs) are inversely correlated to the age, and the LTLs are associated with the GDF11 expression level in patients who suffered coronary artery diseases (Opstad et al., 2019), implying that GDF11 is associated with telomere length but no causal evidence has been provided.