How Human Growth Hormone Is Produced in the Pituitary Gland

If your child has been diagnosed with pediatric growth hormone deficiency (GHD), you may feel like you have a steep learning curve ahead of you. You’ve likely heard of human growth hormone (HGH), but how and where is it produced? And what exactly causes it to run low in some children?

The answers to these questions lie within the pituitary gland.

“Growth hormone deficiency is what the name implies; the pituitary gland does not make enough growth hormone. It usually starts to present itself at around age four, but can also show up during puberty,” says Supamit Ukarapong, M.D., the medical director of pediatric endocrinology at Johns Hopkins All Children’s Hospital in St. Petersburg, FL.

Whether your child is in the younger age window or they are in the midst of puberty, it is the workings of their pituitary gland that will be at the center of their treatment for GHD. Let’s take a closer look at what that means.

Understanding the Pituitary Gland’s Role in Growth

The pituitary gland is responsible for controlling your child’s growth but it does a lot more, too. In fact, it is often called the “master gland” because it controls the activity of most other hormone-secreting glands, including the thyroid and adrenal glands. The pituitary thereby has a hand in a host of important functions such as metabolism, sexual maturation, reproduction, blood pressure, and more, according to the Society for Endocrinology.

This small, pea-sized gland consists of two lobes: a front (anterior) lobe and a back (posterior) lobe. It is housed at the base of the brain and its main job is to secrete hormones: Some hormones, like human growth hormone, are secreted directly into the bloodstream, while others are funneled to other glands for release.

So what starts off this cascade effect?

The pituitary gland is attached to the hypothalamus, the structure that serves as a sort of orchestra conductor in keeping your body functions balanced. Via a connection of blood vessels and nerves called the pituitary stalk, the hypothalamus communicates with the pituitary gland, sending hormone messengers that either cue the release of other hormones like human growth hormone or signal to turn off the tap. In this way, the pituitary consistently pumps out HGH in short bursts all day long.

“Proper nutrition and fasting during sleep hours are two factors that enhance how the hypothalamus stimulates growth hormone’s release from the pituitary. In fact, growth hormone is released in the greatest amount during sleep, making sleep therefore really important for growth,” says Robert W. Benjamin, M.D., a pediatric endocrinologist at Duke Children’s Health Center Endocrinology Clinic in Durham, NC.

Once released, growth hormone exerts most of its growth effects “by signaling the production and release of insulin-like growth factor hormones from the liver called IGF hormones,” explains Dr. Benjamin. These IGF hormones (also known as somatomedins) are proteins that stimulate the growth of many different types of cells throughout the body, including those in muscles, organs, cartilage, and bone.

By stimulating growth in those latter two components—cartilage and bone—the IGF hormones increase height in children, up until the growth plates (or zones of cartilage) at the ends of their bones have fused. That generally occurs at the end of puberty, or around age 13 to 15 for girls and age 15 to 17 for boys. (Even when children attain their full height, growth hormone continues to be released as it plays other important roles in controlling blood cholesterol, and maintaining muscle mass and bone strength.)

When There Is a Growth Hormone Deficiency

Ever wondered what exactly is behind those growth spurts you went through as a kid? “Growth hormone production is highest in infancy and then again during puberty,” says Dr. Benjamin. “On average, a baby will grow about four inches per year and then, at about age three, the child willaverage two to three inches yearly.”

That said, keep in mind, “some growth slowing within the first couple of years is normal and does not reflect a growth hormone deficiency,” says Dr. Benjamin. “Although there is no hard and fast cutoff, by age three your child should then be on their growth curve.” If not, it can mean your child’s body is not stimulating the production of enough human growth hormone. Simply put, when the pituitary gland fails to release enough growth hormone in those short bursts, the liver likewise does not get the signal to ramp up the release the IGF hormones that can act as Miracle Gro for bones and cartilage.

But why the pituitary short circuit? Many cases of GHD are deemed idiopathic, meaning the cause of the pituitary gland’s disfunction cannot be determined. In other instances, GHD can be the result of a genetic birth defect affecting the pituitary gland; this is congenital hormone deficiency. “Those babies usually have other problems that we see that help us diagnose GHD,” says Dr. Ukarapong. “For instance, the pituitary gland is also responsible for blood sugar control, so if we see irregularities there right after birth, we do tests to confirm GHD.”

In certain cases where GHD is determined to be an acquired condition, there has been discernible damage to the pituitary gland; this can occur through various means including a tumor, radiation therapy, and brain trauma.

Diagnosing Pediatric Growth Hormone Deficiency

Doctors use growth charts as references for normal growth in children; these guides also help them screen for GHD. “If a child is smaller than average but not significantly so, we may wait between six months to a year to see if the growth improves,” says Dr. Ukarapong. “But if a child is way below, and their arms and legs look proportionally short, we’ll test.”

The growth hormone stimulation test is done in an outpatient endocrinology clinic and takes between two to five hours. Medicine to stimulate the pituitary gland to produce growth hormone is delivered through an IV. “If the [amounts of growth hormone produced] are below the expected range, that’s confirmation of GHD,” says Dr. Ukarapong.

Another tool your doctor may use to decide whether or not to take a wait-and-see approach or begin treatment right away is a hand x-ray called a bone age study. “We are able to see the maturity of the bones and if they are behind,” says Dr. Ukarapong. “Say we have a child who is 12 years old and their bone maturity is equivalent to a 10 year old, that’s a significant delay so we would not wait on treatment.”

According to the Endocrine Society, about one in 4,000 to 10,000 children have GHD. Parents often worry that a GHD diagnosis means there is something wrong with the brain. The good news: In the vast majority of pediatric growth hormone deficiency cases, the symptoms are physical, not cognitive. “It only occurs in approximately 2% of cases,” says Dr. Ukarapong. Still, to rule neurological complications, once the blood work confirms GHD, your doctor will likely want to do an MRI of your child’s brain. While most kids fare fine with the MRI machine, “sometimes we sedate the child if they are afraid of being in a small (loud) place for a long time,” says Dr. Ukarapong.

Beginning the Treatment Journey for Pediatric GHD

As overwhelming as a diagnosis can be for parents, it’s important to know that doctors have very effective means for treating growth hormone deficiency in children. Your pediatrician will discuss the treatment options, which essentially involve administering a synthetic hormone shot that is similar to the growth hormone that the body produces.

Of course you’ll have plenty of questions. Start here: This brief guide can help you know what things to discuss with your doctor to get clarity on your child’s treatment plan. And meanwhile, take heart, says Dr. Benjamin. “Patients are usually thrilled to learn the treatment for GHD is no longer needed past their teen years,” he notes. “So it’s really not a bad diagnosis.”

Notes: This article was originally published August 1, 2023 and most recently updated August 3, 2023.