Learn the basics of severe primary IGF-1 deficiency.

Signs and symptoms.

Although children with SPIGFD are typically normal size at birth, they grow more slowly during infancy and childhood. They have normal body proportions, but because of their small size, they appear younger than their calendar age.

Understanding IGFD types

Children with idiopathic short stature (“idiopathic” means the cause has not been identified) are often treated with growth hormone replacement therapy, but they may not respond—because their growth hormone levels aren't actually low.

When a child is diagnosed with idiopathic short stature and does not respond to growth hormone therapy, a reevaluation might be needed. This involves the doctor checking to see if the patient is taking their medication, if the growth hormone dose needs to be adjusted, or if another diagnosis—such as severe primary IGF-1 deficiency (IGFD)—should be considered.

Understanding severe primary IGFD - a disorder defined by low IGF-1 levels

Insulin-like growth factor deficiency, or IGFD, is a big word that describes lower levels in the body of IGF-1, a naturally occurring hormone that plays a central role in human growth. Sometimes you hear IGFD classified as secondary IGFD, primary IGFD or severe primary IGFD:

  • Secondary IGFD happens in children whose IGF-1 levels are low; this may be due to their bodies' inability to produce enough growth hormone, poor nutrition, thyroid problems or other factors
  • Primary IGFD may happen when IGF-1 levels are low, even though growth hormone levels are normal or even high
  • Severe primary IGFD is a type of primary IGFD in which IGF-1 levels are exceptionally low, despite sufficient or high growth hormone levels

Taking many factors into account

Before making a diagnosis of severe primary IGFD, the doctor will likely do all of the following: perform a thorough evaluation, check height and weight, do a bone scan, and test the levels of growth hormone and IGF-1. Here are the key factors that point to the diagnosis:

  • The child is shorter than almost all other children of the same age and sex, and
  • Levels of IGF-1 in the body are much lower than normal, and
  • Levels of growth hormone in the body are normal or even high


Important Safety Information

Who should not receive INCRELEX?

Your child should not receive INCRELEX if your child: is allergic to mecasermin or any of the ingredients in INCRELEX; has finished growing; has any cancerous tumors or growths; or has a history of cancer. Your child should never receive INCRELEX through a vein.

What should I tell my child’s doctor before my child starts INCRELEX?

Tell your child's doctor about all of your child's medical conditions, including if your child has diabetes; a curved spine (scoliosis); or is pregnant or breast-feeding.

Tell your child’s doctor about all the medicines (prescription and over-the-counter), vitamins, and herbal supplements your child takes. Especially tell your child’s doctor if your child takes insulin or other anti-diabetes medicines; a change in dose may be needed.

What are the possible side effects of INCRELEX?
INCRELEX may cause serious side effects, including:

  • Low blood sugar (hypoglycemia). INCRELEX may lower blood sugar levels. It is important to only give your child INCRELEX 20 minutes before or 20 minutes after a meal or snack to reduce the chances of low blood sugar. Do not give your child INCRELEX if your child cannot eat. Signs of low blood sugar include: dizziness; tiredness; restlessness; hunger; irritability; trouble concentrating; sweating; nausea; and fast or irregular heartbeat. Severe low blood sugar may cause unconsciousness, seizures, or death. Your child should avoid participating in high risk activities (e.g. driving, exercise, etc.) within 2 to 3 hours after an INCRELEX injection, especially at the beginning of treatment. Your child should always have a source of sugar such as orange juice, glucose gel, candy, or milk available in case symptoms of low blood sugar happen. For severe low blood sugar, if your child is not responsive and cannot drink sugar-containing fluids, you should get emergency medical help for your child right away.
  • Allergic reactions are a serious but common side effect of INCRELEX. Call your child’s doctor right away if your child gets a rash or hives, which generally appear minutes to hours after the injection and may sometimes occur at many places on the skin. Stop taking INCRELEX and get medical help right away if your child has trouble breathing or goes into shock, with symptoms like dizziness, pale, clammy skin or passing out. INCRELEX can also cause reactions at the injection site including: loss of fat (lipoatrophy); increase of fat (lipohypertrophy); pain; redness; or bruising.
  • Increased pressure in the brain (intracranial hypertension). INCRELEX, like growth hormone, can sometimes cause a temporary increase in pressure within the brain. Symptoms include persistent headache and nausea with vomiting.
  • Enlarged tonsils. Signs include: snoring, difficulty breathing, sleep apnea (a condition where breathing stops briefly during sleep), or fluid in the middle ear.
  • A bone problem called slipped capital femoral epiphysis, when the top of the upper leg bone (femur) slips apart. Get medical help right away if your child develops a limp or has hip or knee pain.
  • Worsened scoliosis (caused by rapid growth).
  • Tumor Growths. Several cases of cancerous tumors have been observed in children who received INCRELEX. Tell your doctor immediately if your child develops any new growths or symptoms of cancer.
  • Benzyl alcohol toxicity. Benzyl alcohol, a preservative in INCRELEX, can cause serious side effects, including death in infants.

The most common side effects of INCRELEX include: low blood sugar (hypoglycemia), injection site reactions, allergic reactions and enlarged tonsils.

These are not all the side effects of INCRELEX. Call your child’s doctor if your child has side effects that are bothersome or that do not go away. You may report side effects to FDA at 1-800-FDA-1088.


INCRELEX® (mecasermin) is a prescription medicine used to treat children who are very short for their age because their bodies do not make enough insulin-like growth factor-1 (IGF-1). This condition is called severe primary IGF-1 deficiency. INCRELEX should not be used instead of growth hormone. It is not known if INCRELEX is safe and effective in children under 2 years of age.

Click here to view Increlex® Full Prescribing Information and Patient Information.


Who should not use INCRELEX®?

Your child should not receive INCRELEX if your child: has any tumors or growths, noncancerous or cancerous; or has a history of cancer or a condition or family history that increases the risk of cancer; is allergic to mecasermin or any of the ingredients in INCRELEX; or has finished growing. Your child should never receive INCRELEX through a vein.

June 24, 2019 Announcement:


Important new safety information about tumor growth (noncancerous and cancerous). Please see Important Safety Information and updated Prescribing Information.

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