Growth Hormone (GH) Test: Purpose, High/Low Levels, Symptoms, Normal Range & Complete Guide
Overview
The Growth Hormone (GH) Test measures the amount of growth hormone present in the bloodstream. Growth hormone is a protein hormone produced by the pituitary gland, a small but powerful organ located at the base of the brain. GH plays a central role in childhood growth, height development, and bone formation. In adults, it helps regulate metabolism, muscle mass, fat distribution, bone density, and overall energy levels.
Doctors recommend a GH test when a person—child or adult—shows signs of abnormal growth, delayed puberty, unexplained weakness, hormonal imbalance, or symptoms suggesting a pituitary gland disorder. Since GH levels rise and fall throughout the day, additional tests such as GH stimulation or GH suppression tests are often needed for accurate diagnosis.
Where Is Growth Hormone Produced?
Growth hormone is made in the anterior pituitary gland. This gland:
- Lies at the base of the brain
- Produces GH in short bursts (pulsatile secretion)
- Releases more GH during sleep, exercise, and stress
Growth hormone works closely with IGF-1 (Insulin-like Growth Factor-1), a hormone produced in the liver. While GH levels fluctuate widely throughout the day, IGF-1 remains more stable and reflects long-term GH activity.
Main Functions and Importance of Growth Hormone
Growth hormone is essential throughout life, but its functions differ between children and adults.
1. Stimulates Growth in Children
GH helps children grow taller and supports the development of:
- Bones
- Muscles
- Organs
It is especially important during childhood and puberty.
2. Regulates Muscle Mass and Fat Distribution
In adults, GH helps:
- Build and repair muscle
- Reduce excess body fat
- Maintain a healthy metabolism
Low GH levels often cause increased fat around the waist and reduced lean body mass.
3. Aids Tissue Repair
GH plays a role in:
- Cell regeneration
- Wound healing
- Recovery from injuries
4. Improves Bone Density
GH strengthens bones by helping them absorb minerals such as calcium.
This reduces the risk of bone weakness and fractures.
5. Regulates Metabolism
GH influences several metabolic processes:
- Breaks down fats to release energy
- Helps maintain stable blood sugar
- Boosts protein synthesis for cell repair
6. Stimulates IGF-1 Production
GH signals the liver to produce IGF-1, which carries out many of the growth-related actions of GH, including:
- Bone growth
- Muscle development
- Cell multiplication
Because IGF-1 levels remain steadier than GH, doctors often check IGF-1 along with the GH test.
Causes of Low Growth Hormone Levels
Low GH levels usually suggest that the pituitary gland is not producing hormones properly. Common causes include:
1. Pituitary Gland Damage
Damage may occur due to:
- Pituitary tumors
- Brain surgery
- Radiation treatment
- Infections
- Poor blood supply to the gland
2. Genetic Growth Hormone Deficiency
Some children are born with mutations that prevent the pituitary gland from producing GH.
3. Hypopituitarism
A condition where the pituitary gland underproduces multiple hormones, including GH.
4. Brain Injury
Head trauma or skull fractures can affect pituitary function.
5. Chronic Illness or Malnutrition
Severe long-term illnesses or poor nutrition can reduce GH production in both children and adults.
Symptoms of Low Growth Hormone Levels
In Children
- Short height
- Slow growth rate
- Delayed puberty
- Increased fat around the waist
- Poor bone development
- Reduced muscle mass
In Adults
- Decreased muscle strength
- Increased body fat
- Fatigue or low energy
- Bone weakness (osteopenia or osteoporosis)
- Anxiety or depression
- Poor quality of life
- Increased sensitivity to cold and heat
Causes of High Growth Hormone Levels
Excess GH is most often caused by conditions that overstimulate the pituitary gland.
1. Pituitary Tumor (Most Common Cause)
A benign tumor called an adenoma can produce excess GH.
2. Genetic or Hormonal Disorders
Certain rare genetic or endocrine problems may lead to high GH levels.
3. Ectopic GH Secretion (Very Rare)
Tumors outside the pituitary gland may produce GH-like hormones.
Symptoms of High Growth Hormone Levels
In Children — Gigantism
- Excessive height
- Abnormally large hands and feet
- Rapid growth rate
- Increased appetite
In Adults — Acromegaly
- Enlarged facial bones
- Thickened skin
- Enlarged jaw (prognathism)
- Large hands or feet
- Coarse facial features
Other Symptoms (Both Children & Adults)
- Headaches
- Vision problems (due to tumor pressure)
- Joint pain
- High blood pressure
- Heart enlargement
- High blood sugar or diabetes
Reference Ranges
Because GH secretion is pulsatile, levels can vary widely. A single measurement may not reflect true GH activity.
Children
- GH levels depend on age and puberty stage
- 10–50 ng/mL may be seen after stimulation testing
Adults
- Baseline fasting GH: < 5 ng/mL
- Stimulation tests are used to diagnose deficiency
- Suppression tests are used to diagnose excess GH
Sample Type
- Blood sample (serum)
- Often collected multiple times
- Used for baseline GH, stimulation tests, or suppression tests
Test Preparation
Preparation depends on the type of GH test being done.
General Preparation
- Fasting may be required (doctor will specify)
- Avoid strenuous exercise before the test
- Inform your doctor about:
- Medications
- Recent illness
- Pregnancy
- Hormonal therapy
For Stimulation or Suppression Tests
- You may need to stay at the testing center for 2–4 hours
- Medicines or glucose may be given to evaluate GH response
- Multiple blood samples will be collected at regular intervals
When to Consult a Doctor
Seek medical care if you or your child experience:
For Children
- Noticeably slow growth
- Declining growth rate
- Short stature compared to peers
- Delayed puberty
- Frequent headaches or vision problems
For Adults
- Persistent fatigue
- Loss of muscle mass
- Increased body fat
- Bone pain or frequent fractures
- Enlarged hands, feet, or facial features
- Headaches or vision disturbances
Early diagnosis of GH disorders helps prevent long-term complications and improves quality of life.
Important Word Explanations
Suppression Test: Test that checks GH excess by reducing hormone levels
Pituitary Gland: Hormone-producing gland located at the base of the brain
IGF-1: Hormone made in the liver that mediates many GH functions
Acromegaly: Condition in adults caused by high GH levels
Gigantism: Excessive growth in children due to high GH
Hypopituitarism: Underactive pituitary gland producing low hormones
Stimulation Test: Test that checks GH deficiency by triggering hormone release
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