Read the full study: The Somatotropic Axis in Neonatal Calves Can Be Modulated by Nutrition, Growth Hormone, and Long-R3-IGF-I (AJP-Endo 1997)
That modification is the key engineering trick: it makes the molecule more resistant to the enzymes that would normally break GHRH down quickly, giving tesamorelin a longer working window than sermorelin while still acting on the same GHRH receptor
3 However, if a couple has concerns about their fertility, a screening history and physical exam can be undertaken at any time
eng Iliceto S, Scrutinio D, Bruzzi P, D'Ambrosio G, Boni L, Di Biase M, Biasco G, Hugenholtz PG, Rizzon P: Effects of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Ecocardiografia Digitalizzata Infarto Miocardico (CEDIM) Trial
Heres the trick
On the other hand, GHK-Cu skips all of that