Growth hormone (GH), also known as somatotropin, is a peptide hormone naturally produced by the pituitary gland that regulates growth, cell reproduction, and metabolism. When therapeutic intervention is necessary, the synthetic version, called somatropin, must be introduced externally. Since this medication is a large protein molecule, it cannot be absorbed effectively if taken orally, necessitating daily or weekly subcutaneous injections. This need for self-administered injectable therapy has driven the development of specialized delivery mechanisms designed to make the process safe, accurate, and comfortable for long-term use.
Conditions Requiring Growth Hormone Therapy
Growth hormone therapy is prescribed only by a qualified healthcare provider, such as an endocrinologist, to treat specific medical conditions involving GH deficiency or certain causes of short stature. In children, treatment is commonly indicated for Growth Hormone Deficiency (GHD), where the pituitary gland does not produce sufficient GH. It is also used to promote growth in conditions like Turner Syndrome, a genetic disorder affecting females, and Prader-Willi Syndrome.
Additional pediatric indications include chronic renal insufficiency and children born small for gestational age who do not experience catch-up growth. For adults, GH therapy is primarily used to treat Adult GHD, which can be a continuation of childhood GHD or acquired later, often due to pituitary tumors or surgery. Adults with GHD benefit from replacement therapy to help regulate body composition, bone density, and lipid profiles.
Understanding GH Delivery Devices
The hardware used to deliver somatropin has evolved significantly from traditional methods to highly advanced electronic systems. The earliest and simplest method involves the traditional syringe and vial, where the medication is drawn manually and injected with a standard needle. This method often requires the user to perform mixing or reconstitution of the powdered GH with a diluent.
The most common option today is the GH pen device, which uses pre-filled cartridges or disposable components. These pens are engineered for user-friendliness, featuring dials that allow the user to precisely select the required dose, which improves dosing accuracy. Pen devices are categorized into disposable pens (discarded after the cartridge is empty) and reusable pens (where the cartridge is replaced).
Autoinjectors represent a further simplification, as they are spring-driven mechanisms that automatically insert the needle and deliver the dose with the push of a button. This feature is helpful for patients who experience anxiety related to the sight of a needle. Electronic injectors integrate digital displays, memory functions to track injection history, and often automated mixing of the medication. Some needle-free injection systems also exist, using high pressure to push the medication through the skin, though their acceptance has been limited compared to the fine needles used in modern pens.
Proper Injection Technique and Site Rotation
Growth hormone is administered subcutaneously, delivered into the fatty layer just beneath the skin, requiring careful technique for efficacy and minimal discomfort. Before the injection, the user should wash their hands and clean the chosen injection site with an alcohol swab, allowing the skin to air-dry completely to prevent stinging. The goal is to deliver the medication into the subcutaneous fat layer without reaching the muscle.
Common injection sites include the abdomen, the outer area of the thighs, and the back of the upper arms. For most modern pen devices using short, fine needles, the needle can be inserted at a 90-degree angle without pinching the skin. If a longer needle is used or the patient is very thin, gently pinching a fold of skin before inserting the needle at a 45-degree angle helps ensure the medication is deposited correctly.
Systematic site rotation is essential for safe, long-term self-administration. Repeated injections into the exact same spot can lead to lipoatrophy (breakdown of fat tissue) or lipohypertrophy (formation of a firm lump). Both conditions interfere with the body’s ability to absorb the medication consistently, reducing its effectiveness. Patients should move the injection location at least an inch away from the previous site, rotating through all available areas before returning to a used spot.
Storage, Handling, and Disposal
Maintaining the chemical stability of somatropin requires strict adherence to specific storage and handling instructions, as it is highly sensitive to temperature and physical agitation. The majority of GH products must be stored under refrigeration, typically between 2°C and 8°C (36°F and 46°F), prior to their first use. It is important to avoid freezing the medication, as this can permanently damage the protein structure and render it ineffective.
Some formulations come as a lyophilized powder and require reconstitution, a process where the user or the pen device mixes the powder with a liquid diluent. During reconstitution and general handling, it is essential not to shake the vial or pen vigorously, as agitation can cause the protein to degrade. Once a pen is in use, its stability at room temperature (not exceeding 25°C or 77°F) is often limited, typically to 21 to 28 days, depending on the specific brand.
Used needles, syringes, and empty disposable pens are considered “sharps” and must be disposed of immediately in a puncture-resistant container to prevent accidental needle-stick injuries.
Sharps Disposal
- This container, often a manufactured sharps box, should be kept out of reach of children and pets.
- When the sharps container is approximately three-quarters full, it must be sealed.
- Disposal must follow local waste management regulations.
- This usually involves dropping it off at a designated collection site rather than placing it in household trash or recycling.