Somatropin (rhGH): effects, approved uses and side effects

Somatropin is genetically engineered human growth hormone. It is used for growth hormone deficiency and for certain conditions that involve short stature. Which uses are approved depends on the individual product. The approval information in this article refers to the US.

What is somatropin?

Somatropin is recombinant human growth hormone. “Recombinant” describes how it is made through genetic engineering: cells are given the human growth hormone gene and use it to produce the hormone. The resulting protein consists of 191 amino acids and is identical to the growth hormone the body makes itself. Brand names include Genotropin, Norditropin, Omnitrope and Zomacton.

According to the manufacturers, Nutropin was discontinued in the US at the end of 2024, and Humatrope is scheduled to be discontinued at the end of 2026.

Newer products such as lonapegsomatropin and somatrogon act for longer. Their molecular structure differs from that of conventional somatropin products.

The history of somatropin

Before growth hormone could be made through genetic engineering, it was extracted from the pituitary glands of people who had died. The pituitary is a hormone-producing gland in the brain. This approach yielded only small amounts.

In 1985 this program was stopped after cases of Creutzfeldt-Jakob disease were linked to growth hormone from human pituitary glands. Contaminated pituitary material had transmitted the fatal disease, in which nerve tissue is destroyed.

Shortly afterward, recombinant human growth hormone was approved for the first time. Making it requires no human pituitary material, which removed the transmission risk that came with it. Recombinant production has been the standard ever since.

How does somatropin work?

Somatropin binds to growth hormone receptors on cells throughout the body. This prompts the liver and other tissues to make insulin-like growth factor 1 (IGF-1). In children, IGF-1 and growth hormone together drive the lengthwise growth of bones at the growth plates. They also promote protein building and fat breakdown and influence carbohydrate metabolism. Somatropin therefore has the wide-ranging effects of the body’s own growth hormone.

In children with growth hormone deficiency and in certain conditions such as Turner syndrome or Prader-Willi syndrome, treatment speeds up growth and increases the height reached in adulthood. In adults with growth hormone deficiency, it improves body composition and metabolic measures.

The body breaks the hormone down quickly, so conventional somatropin has to be injected every day. Growth during treatment and IGF-1 levels are used to adjust the dose.

Is somatropin FDA-approved?

Yes. The US Food and Drug Administration (FDA) has approved somatropin products. Humatrope, approved in 1987, is one of the early products; many other brands followed.

Each approval covers specific indications. These include growth hormone deficiency in children and adults as well as certain syndromes. The uses covered by an individual product are stated in its product information, for example in the US prescribing information for Norditropin.

What is somatropin prescribed for?

Somatropin is used in children and adults with growth hormone deficiency. Depending on the product, it may also be used for short stature associated with the following conditions or findings:

• Turner syndrome
• Prader-Willi syndrome
• chronic kidney disease
• Noonan syndrome
• SHOX deficiency
• being born too small or too light for gestational age (small for gestational age)
• idiopathic short stature, meaning short stature with no identified cause

Some products are also approved to treat HIV-associated wasting syndrome, in which people lose a marked amount of body weight and body mass.

What are the side effects?

Which side effects are common varies from product to product. They include:

• injection site reactions
• joint and muscle pain
• swelling from fluid retention
• headache

There are also more serious risks and warnings:

• Somatropin can reduce insulin sensitivity and raise blood sugar levels.
• There is an explicit warning against use in people who are acutely critically ill. In studies, growth hormone increased mortality in this situation.
• Sudden deaths have been reported in people with Prader-Willi syndrome who have severe obesity or breathing problems. For this reason, breathing is assessed before and during treatment.
• Other risks include raised pressure inside the skull, slipping of the head of the thighbone at the growth plate, and worsening of scoliosis in children.
• Growth of existing tumors, inflammation of the pancreas (pancreatitis) and severe allergic reactions are also among the risks.