Always ask for sources with ChatGPT. For example..
Short answer: carbohydrates (via insulin) suppress endogenous (natural) GH secretion from the pituitary, but they do NOT meaningfully blunt the biological action of exogenous (injected) growth hormone. This is the key distinction that bodybuilding forums often miss.
- Insulin/carbs suppress endogenous GH (this part is true) Veldhuis et al., 2005 – Endocrine Reviews
“Regulation of growth hormone secretion”
Hyperglycemia and hyperinsulinemia markedly suppress spontaneous and stimulated GH secretion. This applies only to pituitary GH release.
Ho et al., 1988 – Journal of Clinical Endocrinology & Metabolism
“Effects of glucose and insulin on GH secretion”
Oral glucose reliably suppresses GH secretion and is the basis of the oral glucose tolerance test used for acromegaly diagnosis.
- Insulin does NOT block exogenous GH receptor signaling or IGF-1 production
Leung et al., 2004 – Journal of Clinical Endocrinology & Metabolism
“Insulin regulation of growth hormone receptor signaling”
Insulin does not inhibit GH receptor activation or downstream STAT5 signaling in the presence of circulating GH.
Yakar et al., 1999 – Proceedings of the National Academy of Sciences (PNAS)
“Circulating IGF-1 is directly regulated by GH receptor activation”
Hepatic IGF-1 production depends on GH receptor activation and is independent of insulin levels within normal physiological ranges.
- Insulin is permissive (supportive), not antagonistic, to GH/IGF-1 anabolism
Thissen et al., 1994 – Endocrine Reviews
“Nutritional regulation of the insulin-like growth factors”
Insulin is permissive for IGF-1 action and enhances anabolic effects in skeletal muscle.
- Why fasted GH can favor fat loss (but is not required for GH to work)
Møller et al., 1990 – Metabolism
“Growth hormone and lipid metabolism”
Placental transfer of flecainide
pubmed.ncbi.nlm.nih.gov
GH-stimulated lipolysis is reduced in the presence of hyperinsulinemia. This affects fat mobilization, not GH efficacy or IGF-1 production.
Bottom line:
Carbs and insulin suppress natural GH secretion, but they do not “turn off” injected GH. Exogenous GH works regardless of insulin levels. Eating carbs near GH injections may reduce acute fat burning, but it does not negate GH’s anabolic or IGF-1–mediated effects.