To achieve adult height, everyone needs GH. But some people are born with inadequate amounts of GH — called congenital growth hormone deficiency — and others may acquire the problem later on.

A deficit in GH in children has been recognized for decades, in large part because the problem is so apparent. Children without enough GH simply don't grow and develop normally. Growth is significantly slowed, and the child often slips to the lower percentages on height and weight charts. Your child may also have delayed puberty.

But the condition was largely unrecognized in adults until the 1990s. That's when experts realized that GH affected virtually every type of body tissue. Experts also learned that a deficit in GH is associated with higher mortality.

GH deficiency most often develops as a result of a problem with the pituitary gland, caused by a tumor or surgery or radiation to treat that tumor. When something goes wrong with the pituitary gland, GH is one of the first hormones to be affected.

Diagnosing GH deficiency involves the use of stimulation testing. One test is called an insulin-tolerance test, in which low blood glucose is achieved by insulin administration. Blood is drawn to measure GH. Another test more widely used is called an Arginine-GHRH test, in which arginine, an amino acid, and GH-releasing hormone are injected into the body. Blood measurements are then done to see how much GH is released.

Adults without enough GH tend to experience a decrease in muscle, an increase in fat, and a reduction in exercise capacity. Some people with GH deficiency will experience sleep problems, fatigue, and depression. Because some of these symptoms are the same as those in hypothyroidism, the two conditions can easily be mistaken for one another.