GH deficiency causes short stature in children. In adults, GH deficiency results in a reduction in muscle mass, an increase in body fat (particularly abdominal fat), and a decrease in bone mineral density. Quality of life, including energy, is also reduced in adults with GH deficiency.

GH deficiency most commonly occurs in conjunction with other pituitary hormone deficiencies. Causes of GH deficiency include large pituitary tumors, a history of pituitary surgery or radiation treatment, or as a complication of traumatic brain injury.

GH levels also decline naturally with age and obesity, but it is unclear whether this age- and weight-related decline is pathologic (abnormal) and whether GH therapy is helpful or harmful in such patients. In addition, GH therapy is not FDA-approved for these conditions.

GH deficiency in children causes short stature. In adults, GH deficiency is associated with adverse changes in body composition. This can include a reduction in muscle mass and strength, as well as an accumulation of abdominal fat. In addition, patients with GH deficiency may develop osteoporosis (bone loss). Quality of life, including energy, also have been shown in studies to be reduced in adults with GH deficiency.

GH deficiency is diagnosed with a GH "stimulation test.” This is a test that typically takes 3-4 hours and must be done by staff with expertise in this area. IGF-1 levels are sometimes useful, but only if they are low, as some patients with normal IGF-1 levels will be shown to have GH deficiency on a GH stimulation test. Studies have shown that there is an extremely high likelihood of GH deficiency in patients with 3 or more other pituitary hormone deficiencies. A random GH level is not useful to diagnosis GH deficiency because GH is pulsatile, meaning the levels go up and down rapidly multiple times per day. Therefore, a low random GH level may simply reflect a normal trough between pulses.

GH deficiency does not need to be treated in adults, and in some cases there are contraindications to treatment (for example, a history of cancer). GH deficiency can be treated with GH injections that are self-administered once daily. A long-acting GH injection self-administered once per week is also available. The GH dose is titrated based on IGF-1 levels. Side effects can include swelling of the hands and feet, which is usually mild and transient, and worsening of glucose control. Therefore, patients with diabetes mellitus or pre-diabetes should be monitored closely if prescribed GH. Carpal tunnel syndrome can be exacerbated by GH therapy. GH is not prescribed to patients with a history of cancer.