Growth Hormone

Purpose of the Growth Hormone Test

• Diagnose Deficiencies (GHD): Used when children have slow growth, short stature, or delayed development.
• Diagnose Excess (Acromegaly/Gigantism): Used in adults or children with rapid, abnormal growth of bones and tissues.
• Monitor Pituitary Function: Evaluates the overall health of the pituitary gland, which produces GH.
• Monitor Treatment: Evaluates the effectiveness of GH replacement therapy.

Types of GH Testing

Because GH levels fluctuate throughout the day, a single random blood sample is rarely used.

• Growth Hormone Stimulation Test: Used if low GH is suspected. Medicines (like arginine or clonidine) are given to force the pituitary to release GH, and blood is drawn over 2-5 hours to see if levels rise.
• Growth Hormone Suppression Test: Used if high GH (acromegaly) is suspected. A sugary drink (glucose) is given, which should naturally suppress GH. Blood is taken to see if levels fail to drop.
• IGF-1 Test: Often, doctors check Insulin-like Growth Factor-1 (IGF-1), a protein produced by the liver in response to GH, because its levels remain stable throughout the day.

Preparation and Procedures

• Fasting: Overnight fasting (no food or drink except water) is required.
• Rest: Patients are often asked to rest for 30-90 minutes before the test because exercise affects GH levels.
• Medication Review: Some medications (steroids, blood pressure meds) might be temporarily stopped by a doctor.
• Procedure: A small, flexible tube (cannula) is usually inserted into a vein to draw multiple samples without repeated needle sticks.