Research brief · 2026-09-09
What Growth Hormone Actually Does in Adults
Growth hormone does not stop mattering when growth stops. It is a 191-amino-acid peptide made by the pituitary gland and released in pulses through the day, with the largest pulse arriving shortly after sleep begins. Much of its downstream work is done by IGF-1, which the liver produces in response and which acts on muscle, bone and other tissues.
In adults, the growth hormone and IGF-1 system helps maintain lean tissue and bone, promotes the breakdown of stored fat, and has effects on blood sugar. Output declines with age. A 2000 study in JAMA by Van Cauter and colleagues, analyzing sleep and hormone records from 149 men, found growth hormone secretion fell across adulthood in parallel with the loss of slow-wave sleep, with most of the decline happening between early adulthood and mid-life.
The clearest test of what growth hormone does in adults is what happens when it is replaced. In adults with true growth hormone deficiency, the Endocrine Society's 2011 clinical practice guideline reports that replacement increases lean mass, decreases fat mass and improves some quality-of-life measures, which is why it is an FDA-approved prescription treatment for that condition.
Healthy older adults are a different story. A 2007 systematic review in Annals of Internal Medicine pooled 31 studies covering roughly 220 participants who received growth hormone. Lean body mass rose by about 2.1 kilograms and fat mass fell by about 2.1 kilograms. Muscle strength did not significantly improve, and treated participants had more soft-tissue swelling, joint pain, carpal tunnel syndrome and glucose problems. The reviewers concluded it could not be recommended as an anti-aging therapy.
The limit is that a change in body composition on a scan is not the same as better function, and the only adult use with an approved evidence base is diagnosed deficiency. Growth hormone is a prescription medication, and any question about it belongs with an endocrinologist.
Sources
- Van Cauter E, Leproult R, Plat L, Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men
- JAMA 2000
- Liu H et al., Systematic review: the safety and efficacy of growth hormone in the healthy elderly
- Annals of Internal Medicine 2007
- Molitch ME et al., Evaluation and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society Clinical Practice Guideline
- Journal of Clinical Endocrinology & Metabolism 2011
Peptide Proof reports what studies found. We do not give medical advice, dosing guidance, or treatment recommendations.