Taking 5 mg of melatonin raised growth hormone by 157% within 40...

When resistance training was performed 60 minutes after ingestion, GH rose again — reaching a 132% increase by the 83rd minute.
Exercise alone (placebo group) likely increased GH by ~50–70%, though exact figures were not reported.
A lower dose of 0.5 mg melatonin led to a 106% increase in GH post-exercise, indicating melatonin's role
Study: PMID: 17956623
Melatonin boosts GH by suppressing somatostatin, enabling GH release even during the day, independent of sleep.
While exercise alone raises GH, it does so to a lesser extent — but it appears to extend the GH response when combined with melatonin, preventing the typical decline after its peak.
That's because the rise of IGF-1 from growth hormone takes several hours - up to 8-24 hours
Thus, it's biologically plausible that the melatonin intervention resulted in higher IGF-1 in 8 hours, although it wasn't measured in this study

