Growth Hormone (HGH)

Function

Human Growth Hormone (HGH), secreted by the anterior pituitary gland, is essential for growth, body composition, cell repair, and metabolism. In children, it is the primary driver of height; in adults, it helps maintain bone density, muscle mass, and healthy adipose tissue distribution. HGH levels fluctuate throughout the day in a pulsatile manner, heavily influenced by the circadian rhythm and physiological stressors.

Why it is Ordered

HGH testing is rarely performed as a single random draw because of its pulsatile nature. It is typically ordered as part of stimulation or suppression tests. It is used to investigate growth delays in children, or in adults to diagnose GH deficiency or excess. Symptoms of excess include enlarging hands and feet or coarsening facial features, while deficiency symptoms include decreased vitality, increased body fat, and decreased bone mass.

Associated Conditions

• Acromegaly: GH excess in adults, usually caused by a benign pituitary tumor.
• Gigantism: GH excess in children before the closure of epiphyseal plates.
• GH Deficiency: Resulting from pituitary damage, trauma, or congenital issues.
• Pituitary Adenomas: Tumors that can either hyper-secrete HGH or crush HGH-producing cells.

Clinical Management

Because HGH levels can be undetectable in healthy individuals during 'troughs,' clinicians often use Insulin-like Growth Factor-1 (IGF-1) as a proxy, as it provides a more stable reflection of 24-hour HGH activity.