Hormonal
Women exhibit higher skeletal muscle expression of GRB10 and ACVR2B compared to men, which may contribute to smaller muscle mass by inhibiting IGF-1 signaling and increasing myostatin activity.
This research highlights a biological basis for why women, on average, have less muscle mass than men, potentially due to higher levels of specific genes (GRB10 and ACVR2B) that inhibit muscle growth signals. For women, this means that building muscle may require specific attention to resistance training to overcome these inherent signaling constraints, rather than assuming equal ease of growth compared to men.
The women had >2-fold greater expression than the men (P<0.0001) of two genes that encode proteins in growth factor pathways known to be important in regulating muscle mass: growth factor receptor-bound 10 (GRB10) and activin A receptor IIB (ACVR2B)... If these sex-related differences in mRNA expression lead to reduced IGF-1 activity and increased myostatin activity, they could contribute to the sex difference in muscle size.
Why this rating
Strong statistical significance (P<0.0001) and replication in an independent cohort, but limited by reliance on mRNA data without protein validation.
Source
Sex-Related Differences in Gene Expression in Human Skeletal Muscle
Stephen Welle et al. · PLoS ONE · 2008
DOI 10.1371/journal.pone.0001385
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