How does muscle grow (evolution, liver/pituitary axis and sexual dimorphism)

sources *GLUT4 / post-exercise glucose uptake* Richter EA, Hargreaves M. Exercise, GLUT4, and skeletal muscle glucose uptake. *Physiol Rev*. 2013;93(3):993–1017. Podcast / interview with Prof. Erik Richter:    • Podcast with Prof Erik Richter - Exercise,...   Knudsen JR et al. (including Richter). Prior exercise in humans redistributes intramuscular GLUT4 and enhances insulin-stimulated sarcolemmal and endosomal GLUT4 translocation. *Mol Metab*. 2020;39:100998. *Muscle memory / myonuclei* Egner IM, Bruusgaard JC, Eftestøl E, Gundersen K. A cellular memory mechanism aids overload hypertrophy in muscle long after an episodic exposure to anabolic steroids. *J Physiol*. 2013;591(24):6221–6230. Bruusgaard JC, Johansen IB, Egner IM, Rana ZA, Gundersen K. Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. *Proc Natl Acad Sci U S A*. 2010;107(34):15111–15116. *GH / IGF-1 axis and androgens* Sjögren K et al. / Yakar S et al. (1999). Liver-specific IGF-1 knockout models showing near-normal postnatal growth despite large reductions in circulating IGF-1. Venken K et al. Impact of androgens, growth hormone, and IGF-I on bone and muscle in male mice during puberty. *J Bone Miner Res*. 2007. *Trenbolone and satellite cells* Kamanga-Sollo E et al. (Dayton group). Papers on trenbolone acetate effects on bovine satellite cells requiring both androgen receptor and IGF-1 receptor (e.g., 2008, 2011). *Sexual dimorphism and androgen action on muscle* Reviews and primary papers establishing that androgen receptor signaling is a major driver of male-biased muscle mass and sexual size dimorphism in mammals (e.g., work on muscle-specific AR knockout mice showing reduced lean mass, and comparative studies linking circulating testosterone to sex differences in muscle). Classic observations on 5α-reductase deficiency and incomplete masculinization of external genitalia / secondary sexual characteristics (supporting tissue-selective amplification of testosterone to DHT). Adrenarche literature: rise in adrenal DHEA/DHEAS in humans and some great apes, with peripheral conversion to active androgens (e.g., reviews in J Clin Endocrinol Metab and primatology papers on catarrhine primates). *Evolutionary conservation of skeletal muscle* Steinmetz PRH et al. / Technau U et al. (2012). Independent evolution and ancient origin of striated-muscle components (including myosin heavy-chain diversification predating animals). Nature / related phylogenetic papers. Broader comparative work showing that the actin–myosin sarcomeric apparatus is present early in metazoan evolution and is shared across vertebrates and many invertebrates (mice, cattle, humans, and fruit flies all use the same basic contractile unit). Reviews noting that local/paracrine signaling systems for muscle are older than the vertebrate circulating GH/IGF-1 endocrine axis.