Growth Hormone

The Growth Hormone test (human growth hormone, hGH) aids in assessing hypothalamic–pituitary axis function when deficiency or excess of GH is suspected. It contributes to the evaluation of short stature and slowed height velocity in children and to the diagnostic workup of acromegaly in adults and gigantism in children. In suspected GH deficiency, dynamic GH stimulation testing—using agents such as insulin, arginine, clonidine, or glucagon—is employed; in suspected GH excess, oral glucose suppression testing is used. IGF-1 serves as a more stable indicator of integrated GH secretion over time. This assay also supports monitoring of therapeutic response and long-term follow-up for recurrence of GH-related disorders, including in individuals who have received cranial irradiation and are at risk for pituitary dysfunction.

Growth hormone secretion is episodic and increases at night; therefore, an isolated fasting GH concentration is of limited diagnostic utility. Dynamic protocols are preferred: pharmacologic stimulation tests help establish GH deficiency, whereas an oral glucose load is used to assess GH suppression in suspected excess. Measurement of IGF-1 complements these procedures by reflecting average GH activity over time. GH drives normal linear growth in childhood and, in adults, contributes to bone mineralization, skeletal muscle mass, and lipid metabolism. Persistent GH excess, most often from a pituitary adenoma, produces gigantism in children and acromegaly in adults and is associated with complications such as type 2 diabetes, hypertension, increased cardiometabolic risk, arthropathy, and shortened life expectancy. Adult GH deficiency can be associated with reduced bone density and altered body composition; however, true GH deficiency is an uncommon cause of these features.