Pituitary News, Issue 2 - Autumn 1996.

Unfortunately, there is no alternative to Growth hormone administration other than by injection. GH can be administered using a simple insulin syringe, a 'pen' device or a 'jet' device.

Richard Stanhope
Great Ormond Street Hospital for Children NHS Trust

Unfortunately, there is no alternative to growth hormone (GH) administration than by injection. GH is a protein and digested in the stomach and therefore has to be given by an alternative route. There have been studies using an intranasal application of GH but this does not appear to be of practical use. However, there are now much smaller molecules that release GH from the Pituitary gland, which may be clinically useful when given by mouth and these are presently under assessment.

From the early 1980s GH was administered by intramuscular injections three times a week. Extensive studies of how best to administer GH were not done until the advent of biosynthetic GH in 1985 and it was then convincingly demonstrated that daily injections were optimal and that subcutaneous was better than Intramuscular injection. The standard method of administering GH is now by daily subcutaneous injections, in both adults and children. Of course, most of our experience from GH administration has been obtained in children and then applied to adult patients.

GH is manufactured as a powder contained in a vial and requires reconstitution with the fluid provided. Fortunately, most vials now come in a multidose formulation containining a preservative, so that the reconstituted GH will last in the refrigerator for approximately ten days, depending on the specific manufacturer's recommendations. A common method to administer GH is using a simple insulin syringe with a fine needle and certainly this method is foolproof and reliable. There are several makes of autoinjectors, which are devices which contain the needle and syringe. At the push of a button, they both insert the needle and give the injection automatically. Certainly for those who are 'needle-shy' this is of enormous advantage and, indeed, the needle is hidden within the autoinjector and not seen by the patient.

'Pen' devices make preparation for injections easier, with GH in solution contained in a 'cartridge' inside the device. The dose in then 'dialled up' before each injection. However, the needle still has to be inserted manually. The disadvantage of pens is the non-continuous dosage (each 'click' represents something like 0.25 to 1.0 units depending on which device is used) and there is a potential waste of GH at the end of the cartridge. Pen devices have enormous advantages in partially sighted patients as the dose can be dialled by listening to the number of 'clicks'. Unfortunately, no device is yet available that combines the ease of the preparation of the pen with the advantages of the needle insertion of an autoinjector.

Two different 'jets' are now available. Jets are devices which administer GH under high pressure through the skin without using a needle! However, pressure settings are difficult to adjust and this may lead to excessive bruising. Many patients find that using a needle is less traumatic in the long-term although a jet may be of potential advantage in 'needle-phobic' patients.

There is no magic-wand to use for daily injections. You need to have careful discussion with a specialist and it may be that several different methods will be tried until the optimum method for you is found. In children, the only carefully performed clinical trial suggested that an autoinjector was preferred over a pen device. All these devices are obtainable free of charge from the various pharmaceutical companies that manufacture GH.