Insulin is used with GH in bodybuilding to enhance anabolic effects, but metformin has been shown to blunt the anabolic response to GH and may reduce muscle growth. Insulin optimizes GH's muscle-building properties while metformin can counteract them by potentially reducing muscle hypertrophy and the effect of GH on muscle glycogen.
Insulin with GH
Anabolic synergy:
Insulin and GH work together to improve protein synthesis and muscle growth.
Risk of hypoglycemia:
Insulin can cause dangerously low blood sugar, a serious risk that is even more pronounced with the use of GH.
Performance-enhancing drug (PED):
Both insulin and GH are banned in sports by the World Anti-Doping Agency.
Metformin with GH
Counteracts GH effects:
Metformin can reduce muscle glycogen and may blunt the anabolic response from GH.
Reduced hypertrophy:
One study found that metformin inhibited muscle hypertrophy in response to exercise, a negative effect on muscle growth.
Increased fat loss:
Some research has shown that metformin can reduce both visceral and subcutaneous fat, but this effect may be counteracted by GH.
No performance enhancement:
Combining GH and metformin has been shown to not improve performance metrics like VO2max.
Key takeaway
For the purpose of muscle building, insulin is used with GH because it is thought to potentiate GH's anabolic effects.
Metformin may interfere with the anabolic effects of GH and is not recommended for use in combination with GH for bodybuilding purposes.
