Growth Hormone
Also known as: GH, HGH, Somatotropin
What Does Growth Hormone Measure?
Growth Hormone (GH), also known as somatotropin or human growth hormone (HGH), is a protein hormone produced and secreted by the pituitary gland, a small gland located at the base of the brain. A blood test for GH measures the concentration of this hormone circulating in the bloodstream at a given moment. Because GH is released in pulses throughout the day—with the largest surge occurring during deep sleep—a single measurement can vary widely, and doctors often use stimulation or suppression tests alongside random GH levels to get a more accurate picture of pituitary function.
Why Does Growth Hormone Matter?
Growth Hormone plays a central role in regulating body composition, metabolism, bone density, and muscle growth throughout life—not just during childhood. In children, adequate GH is essential for normal linear growth and development; deficiency leads to short stature, while excess causes gigantism. In adults, GH continues to influence fat distribution, muscle mass maintenance, cardiovascular health, and energy levels. Abnormal GH levels are associated with conditions such as acromegaly (excess GH in adults), pituitary tumors, hypopituitarism, and metabolic disorders. Evaluating GH is critical for diagnosing growth disorders, monitoring pituitary function, and guiding hormone replacement therapy.
Normal Ranges
Males
0.01–3.0 ng/mL (random, fasting); stimulation test peak >10 ng/mL considered normal
Females
0.01–8.0 ng/mL (random, fasting); slightly higher due to estrogen influence
Children
Varies by age and pubertal stage; stimulation test peak >10 ng/mL generally considered normal
Causes of High Levels
- Pituitary adenoma (GH-secreting tumor) — the most common cause of chronically elevated GH, leading to acromegaly in adults or gigantism in children
- Acromegaly — a condition caused by a GH-secreting tumor producing excess hormone in adults, resulting in enlarged hands, feet, and facial features
- Ectopic GH secretion — rare tumors in the lungs, pancreas, or other organs that secrete GH or GHRH outside the pituitary
- Stress, exercise, or hypoglycemia — physiological triggers that cause transient spikes in GH through normal regulatory pathways
- Fasting or malnutrition — paradoxically raises GH levels as the body attempts to preserve muscle and mobilize fat for energy
- Poorly controlled type 1 diabetes — insulin deficiency impairs IGF-1 feedback, causing compensatory GH elevation
Causes of Low Levels
- Growth hormone deficiency (GHD) — caused by pituitary gland damage, tumors, surgery, or radiation therapy reducing GH production
How to Improve Your Growth Hormone
Diet
- Consume adequate dietary protein (1.2–2.0 g/kg body weight daily) to support GH synthesis and IGF-1 signaling
- Practice intermittent fasting or time-restricted eating, as short-term fasting significantly stimulates GH secretion
- Reduce refined carbohydrates and sugar intake — high insulin levels suppress GH release
- Include foods rich in arginine (nuts, seeds, legumes, meat) and glutamine (eggs, dairy, leafy greens), which are amino acids that support GH secretion
- Avoid large meals close to bedtime, as elevated insulin at night blunts the nocturnal GH surge
Supplements
- L-Arginine: 5–9 g taken before sleep or exercise may modestly increase GH secretion by inhibiting somatostatin
- GABA (gamma-aminobutyric acid): 3–5 g at night has been shown in small studies to increase GH levels during rest
- Melatonin: 0.5–5 mg at bedtime may enhance the nocturnal GH pulse by improving sleep quality and depth
- Vitamin D3: 1,000–4,000 IU daily to maintain adequate levels, as deficiency is associated with reduced GH secretion
- Zinc: 15–30 mg daily supports pituitary function and has been shown to increase GH levels in deficient individuals
Related Biomarkers
Frequently Asked Questions
What is the difference between a random GH test and a GH stimulation test?
A random GH blood test simply measures the hormone level at a single point in time, which can be misleading because GH is released in pulses and levels naturally fluctuate throughout the day and night. A GH stimulation test is a more reliable diagnostic tool where substances like insulin, arginine, or glucagon are administered to trigger GH release, and the pituitary's peak response is measured. Doctors typically use stimulation testing to diagnose GH deficiency, while suppression tests (using an oral glucose load) are used to diagnose excess GH in conditions like acromegaly.
Can adults have growth hormone deficiency, and how does it affect them?
Yes, adults can develop GH deficiency, most commonly following pituitary gland damage from a tumor, surgery, radiation therapy, head trauma, or autoimmune conditions. Adult GHD is different from childhood GHD and does not affect height, but it significantly impacts quality of life and metabolic health. Symptoms include increased body fat (especially around the abdomen), reduced muscle mass and strength, decreased bone density, fatigue, poor concentration, low mood, and increased cardiovascular risk. Treatment with recombinant GH injections can improve many of these symptoms under medical supervision.
Is using human growth hormone for anti-aging or bodybuilding safe?
Using synthetic HGH for anti-aging or performance enhancement outside of a diagnosed medical condition is not recommended and carries significant health risks. While GH does decline with age, supplementing without a deficiency can cause serious side effects including joint and muscle pain, carpal tunnel syndrome, fluid retention, insulin resistance, type 2 diabetes, and potentially increased risk of certain cancers. It is also banned in competitive sports. Legitimate GH therapy is only FDA-approved for diagnosed GH deficiency, HIV-related wasting, short bowel syndrome, and specific pediatric growth disorders.