Sermorelin is a GHRH analog with a genuine prescribing history. As a starting point it's reasonable; the physique and anti-ageing outcomes commonly attached to it are weakly evidenced.
With limited or no human safety data for this combination, there is no established marker set to monitor against — which is a reason for more caution, not less. Baseline bloods and a clinician conversation matter here. General information, not medical advice.