Human Growth Hormone and Growth Disorders

by Susan Terry, MS | March 18, 2026

Human Growth Hormone & Growth Disorders | Brain Builder

Case study video explaining growth disorders with a patient example!

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Overview

In July 1940, Robert Wadlow of Illinois passed away at the age of only 22. At 8 feet 11 inches tall, he was the tallest human to ever live. In this Brain Builder, we are going to learn more about human growth hormone - the secret to Robert's height.


A person standing next to a person AI-generated content may be incorrect.

Robert Wadlow, left, with his father, who was 5ft 11 inches tall.

Wadlow had a pituitary tumor, which caused him to produce excessive amounts of human growth hormone. In this Brain Builder, you will learn about human growth hormone (HGH) and the impact it has on the body. 

Background Information

Human Growth Hormone (HGH) is secreted by the anterior pituitary gland. One of the most notable functions of HGH is controlling growth in children. Specifically, HGH targets cartilage cells called chondrocytes at the epiphyseal growth plate, causing the long bones to lengthen. The cells at the growth plate divide, grow, enlarge, and secrete the extracellular bony matrix seen in bones. These areas create new bone growth in children and young teenagers. Another important function of HGH is to stimulate the liver to produce insulin-like growth factor (IGF), which mediates cell division and cell differentiation, as well as cellular death. IGF acts as a “stop signal”.  Because the amount of HGH produced decreases as a person ages, HGH also plays a role in aging, causing reduced muscle mass and lower bone density. 

Core Concepts

Human growth hormone (HGH) is a protein-based hormone (called a polypeptide) secreted by the pituitary gland, and it regulates body growth. HGH is released in short bursts. The hypothalamus is a part of the brain that acts as a relay station, signaling to the pituitary when it should release growth hormone and when it should not. It secretes different types of releasing hormones and inhibiting hormones that affect the pituitary gland, which hangs by a stalk below the hypothalamus. The hypothalamus secretes growth hormone-releasing hormone (GHRH) and somatostatin, which is an HGH inhibitor. GHRH and somatostatin signal the pituitary to start or stop releasing growth hormone to the body.

HGH’s functions include:

  • Increasing protein production causes an increase in muscle mass and decreases the amount of body fat. 

  • Targeting the epiphyseal growth plates in long bones. A person who secretes HGH in the normal range will have normal height, but height varies greatly and has genetic components. 

  • Keeping your blood glucose stable, which maintains metabolism, maintains normal body structure, and is important after an individual finishes growing.

Problems that can result from HGH secretion: 

  • In adults, human growth hormone can also affect the bones of the hands, feet, and face, causing acromegaly. The person’s height is not affected because their epiphyseal growth plates have fused. People who have acromegaly have a large protruding jaw and large hands and feet. HGH also triggers the liver to produce IGF-1, which causes abnormal growth of the bones.  People with this condition often have a heart problem called cardiomyopathy and other complications from enlarged organs. They may have sleep apnea and also have swollen hands and feet. 

  • A tumor can cause the pituitary gland to secrete an excessive amount of HGH. The person may suffer from gigantism and possibly reach a height of over eight feet. Like Robert Wadlow, many people who are over seven feet tall also have a pituitary tumor.

  • A person whose pituitary gland secretes HGH in low amounts may have pituitary dwarfism. This individual has normal body proportions but is very short and smaller than average. To meet the criteria for dwarfism, one must have a height of four feet ten inches or less.

Diagnosis

Physical examination: At well-child doctor visits, the physician records the child’s height. If they are considered very tall for their age or extremely short, the doctor may order lab tests to measure the level of HGH in the child’s blood as well as IGF. A standard blood test would be  inconclusive since HGH is produced in bursts, not at a constant level. If the doctor suspects an HGH problem, they might take blood over several hours to measure proteins that are related to HGH production as well as the level of IGF1. The doctor will also test the HGH blood level to rule out other potential problems.  

The doctor may also set up pituitary gland response testing, where the gland is stimulated with human growth hormone.

Symptoms of problems with lower-than-usual HGH levels in the blood:

In adults:

  • Higher amount of fat around the waist
  • Lack of stamina
  • Less muscle
  • Reduced bone density/higher risk of fracture
  • Reduced LDL and total cholesterol, but higher lipoprotein

In children:

  • Very slow growth – well below average
  • Less than the 3rd percentile on the growth curve
  • Prominent forehead
  • Immature appearance compared to peers
  • Less developed bridge of the nose

In both children and adults, a full medical history and family history are important for diagnosing a problem with HGH levels. Previous cancer treatment, particularly radiation involving the head, is an important piece of information.

Symptoms of problems with higher-than-usual HGH levels in the blood:

In adults:

  • Large hands, feet, and a prominent jaw
  • Headaches and vision problems due to if a pituitary tumor is present
  • Deepened voice from cartilage growth
  • Joint pain
  • Organ enlargement

In children:

  • Very rapid growth exceeding the 97th percentile on pediatric growth charts
  • Wide fingers and toes
  • Joint pain and weakness from rapid growth
  • Enlarged facial features
  • Excessive sweating and body odor

MRI of the pituitary gland

The doctor would look for damage to the pituitary gland or the presence of a tumor. The doctor would also look at the hypothalamus for damage or a tumor.

Treatments

  1. A person with a pituitary tumor would be observed with imaging studies every few months. A growing tumor would indicate the need for surgery. A child who is excessively tall - reaching a height of six feet for women and six feet eight inches for men - before their growth plates are fused with a pituitary tumor would be advised to have the tumor surgically removed.
  2. A child who has an HGH deficiency would be prescribed daily injections of synthetic human growth hormone. This treatment will probably last for several years, but results can be seen in months. The earlier a child is diagnosed, the more likely it is that they will reach full adult height
  3. A child who has a mutation that makes their cells resistant to human growth hormone would be treated with synthetic IGF injections
  4. An adult with low HGH would also be prescribed daily HGH injections. Signs of getting too much HGH include painful joints, swelling, and pain or numbness in the hands. The dosage would need to be adjusted downward to reduce the side effects.

Both adults and children who are treated with daily HGH injections should be closely monitored by their doctor. 

Unfortunately, HGH injections can be used in unethical ways. Some athletes who greatly desire to increase their muscle mass and feel they are not successful enough with usual bodybuilding methods may turn to HGH injections. These are often obtained from people who are not doctors. It is impossible to be sure that the medical compounds in these injections are safe. Additionally, it goes against many professional sports leagues' code of conduct to take performance-enhancing substances. In 2013, Major League Baseball had a major scandal involving a clinic providing HGH to players. Now, testing positive for HGH will earn a player an 80-game suspension on his first offense and a 162-game season-long suspension on his second offense. Long-term use of HGH in this fashion can cause problems with the cardiovascular, muscular, and reproductive systems.

Key Terms:

Acromegaly – typically from a pituitary tumor, it is caused by HGH affecting the bones of the hands, feet, and face at a greater rate

Gigantism – typically from a pituitary tumor, it is caused by excessive growth of long bones – the tallest ever, Robert Wadlow,   8 ft. 11 inches

Pituitary dwarfism – caused by the pituitary gland secreting excessively low amounts of HGH, resulting in normal body proportions and a height of four feet ten inches or less.

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