Growth Hormone
Overview
Growth hormone (GH) measures a peptide hormone secreted by the anterior pituitary gland in pulsatile fashion that stimulates insulin-like growth factor-1 (IGF-1) production in liver and promotes linear growth, protein synthesis, and lipolysis. It binds membrane receptors to activate JAK-STAT signaling. Elevated levels indicate acromegaly or gigantism from pituitary adenoma, while low levels suggest GH deficiency, hypopituitarism, or Laron syndrome. GH testing is clinically useful for diagnosing GH excess or deficiency when IGF-1 is equivocal, typically requiring dynamic stimulation or suppression testing due to pulsatile secretion.
Clinical Use Cases
- Diagnosing acromegaly/gigantism (with IGF-1 and oral glucose tolerance test).
- Evaluating growth failure or short stature (stimulation testing).
- Assessing hypopituitarism after pituitary surgery or traumatic brain injury.
- Monitoring treatment response to GH therapy or somatostatin analogs.
Specimen Types
- Serum.
- Plasma (EDTA or heparin for some assays).
Measurement Methods
- Immunoradiometric assay (IRMA).
- Chemiluminescent immunometric assay.
- Two-site sandwich immunoassay.
Test Preparation and Influencing Factors
- Requires dynamic testing: stimulation (ITTs, arginine, GHRH) or suppression (OGTT).
- Obesity blunts GH response; malnutrition or hypothyroidism enhance it.
- Estrogen therapy increases GH levels; glucocorticoids suppress.
- Stress, exercise, sleep, fasting influence pulsatile secretion.
Synonyms
- Human growth hormone (hGH).
- Somatotropin.