Histrelin Implant

What is a histrelin implant used for?

A histrelin implant is used to treat early-onset puberty otherwise known as precocious puberty. This means that your child’s puberty started earlier than normal. When your child’s body is ready to begin puberty, the brain tells the pituitary gland (a pea shaped gland located at the bottom of the brain) to release hormones called gonadotropin-releasing hormone (GnRH). GnRH produces two more hormones called luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH cause ovaries and testicles to produce sex hormones called estrogen and testosterone. The production of estrogen and testosterone initiates sexual development. Your child should have already been seen by an endocrinologist to make a diagnosis of central precocious puberty. The work up usually consists of:
  1. Hormone testing (usually a GnRH stimulation test to check your child’s hormone levels this test can determine whether your child's precocious puberty is gonadotropin-dependent or gonadotropin-independent.) 
  2. Bone age: An x-ray of the non-dominant hand can help determine your child’s bone age. It is then compared to standard growth charts to establish whether the bones are growing too quickly 
  3. Head MRI: Occasional this is done, to see if there are any abnormalities that may be causing an early start of puberty
Precocious puberty results in faster than normal bone growth and development of sexual characteristics, in girls usually between 2 and 8 years of age and in boys usually between 2 and 9 years of age.  A histrelin implant is in a class of medications called gonadotropin-releasing hormone (GnRH) agonists. They work by blocking the hormones coming from the pituitary gland that trigger puberty (LH/FSH). The implant releases histrelin slowly and continuously over 12 months.The implant will be left in place for at least one year and evidence has shown that the implant may sometimes be left in longer than one year depending on symptoms. After this time, it can be replaced or removed. Usually when used in children with precocious puberty, histrelin will likely be stopped by your child's endocrinologist before 11 years of age in girls and 12 years of age in boys.

What will happen in the hospital?

Histrelin comes as an implant (a small, thin, flexible tube containing medication) that is inserted by a doctor on the inside of the upper arm. The surgeon places it into your child’s non dominant arm. Some children may need a light general anesthesia, or sleeping medicine, for the procedure. The surgeon will also use a medication to numb the arm, make a small cut in the skin, and then insert the implant subcutaneously (just under the skin). The cut will be closed with stitches or surgical strips and covered with a bandage.

When will my child be discharged?

Usually, once your child is awake, able to tolerate some food and their pain is well controlled they will likely be discharged from the PACU. The operation is usually done as a day surgery. Your child’s arm may be sore after surgery. Your child may take Tylenol or Motrin over the counter every 4-6 hours as needed. Your child should not lift heavy things for 7 days after the implant is placed.

What will be my child's recovery?

Most children do not have severe pain after a histrelin implant placement. Most often over-the-counter pain relievers such as Children's Tylenol or Children's Advil are adequate for pain control. Keep the area around the implant clean and dry for 24 hours after insertion. Do not swim or bathe during this time. The bandage should remain in place for at least 24 hours. The steri-strips should remain in place for at least ten days after the surgery. Your child may shower but should not tub bathe or swim for two weeks until incisions have healed.

What should I be looking out for after the operation?

Once the surgical incision heals, you and your child will likely be able to feel the implant, but it should not cause pain or discomfort. The histrelin implant may cause an increase in certain hormones in the first few weeks after insertion. Your child will continue to be followed by an endocrinologist post-operatively to make sure that his or her LH/FSH are appropriately suppressed by the histrelin and to track his or her growth rate and make sure puberty doesn’t progress. New or worsening symptoms of sexual development may occur during the first few weeks after the insertion of the implant. In girls receiving histrelin implant for precocious puberty, light vaginal bleeding or breast enlargement may occur during the first month of treatment. This will stop once the FSH and LSH are suppressed. When the precocious puberty has been adequately treated, you will return to have the implant removed. This involves a similar process of a light anesthetic and similar wound care postoperatively. Some children need to return for placement of one or two more implants based upon their symptoms.