Growth hormone (GH) therapy is provided in the form of human recombinant GH and comes in subcutaneous injection form.
The starting dose of human growth hormone (HGH) depends on the age and clinical condition of the patient.
HGH Benefits for Adults
Adults who have a growth hormone deficiency — not the expected decline in growth hormone due to aging — might be prescribed synthetic HGH by their doctors.
In most people, growth hormone deficiency is caused by a benign tumor on the pituitary gland (pituitary adenoma) or by treatment of an adenoma with surgery or radiotherapy.
For adults who have a growth hormone deficiency, injections of HGH can:
- increase exercise capacity;
- increase bone density;
- increase muscle mass;
- decrease body fat.
HGH treatment is also approved to treat adults with AIDS- or HIV-related growth hormone deficiency that causes the irregular distribution of body fat.
How does HGH treatment affect healthy older adults?
Studies of healthy adults taking human growth hormone are limited and contradictory. Although it appears that human growth hormone can increase muscle mass and reduce the amount of body fat in healthy older adults, the increase in muscle doesn’t translate into increased strength. It isn’t clear if human growth hormone provides other benefits to healthy adults.
HGH Dosing Regimen
A dosing regimen that is based on age along with dose titration has been associated with fewer adverse effects compared with a weight-based regimen. The following regimen is suggested:
- age younger than 30 years: 0.4-0.5 mg/day (may be higher for patients transitioning from pediatric treatment);
- age 30-60 years: 0.2-0.3 mg/day;
- age >60 years or those with diabetes mellitus or prediabetes: 0.1-0.2 mg/day.
For patients with adherence issues, a less frequent dose regimen such as alternate days or 3 times per week using the same total weekly dosage can be used.
Follow-up is usually planned at intervals of 1-2 months when the dose of GH can be adjusted by increments of 0.1-0.2 mg/day based on the clinical response, serum insulin-like growth factor-1 (IGF-1) levels, and side effects. Longer time intervals and smaller dose increments are suggested for older patients.
Serum IGF-1 levels are the main determinant for adjusting the dose of GH. No studies are available to guide this decision. A commonly used target is the upper half of the normal range appropriate for age and sex unless significant side effects develop.
Once maintenance doses of GH are achieved, follow-up is provided at intervals of 6 months. Monitoring includes clinical evaluation, assessment of side effects, and measurement of serum IGF-1, fasting glucose, and lipid profile.
Quality of life (QOL) is also assessed using standardized questionnaires. If the initial bone mineral density findings, measured by dual-energy x-ray absorptiometry (DXA) scanning, are abnormal, repeat testing at intervals of 2-3 years is recommended.
No studies are available regarding the optimal length of GH replacement therapy. Patients with childhood GH deficiency who attained adult height and had persistent deficiency on retesting should continue to receive GH therapy.
GH therapy can also be continued indefinitely if benefits such as significant improvement in QOL and objective improvements in biochemistry and body composition are observed. If no objective or subjective benefits are seen after 1 year of treatment, discontinuation of GH therapy should be considered.
What are the risks of HGH treatment?
HGH treatment might cause a number of side effects for healthy adults, including:
- Carpal tunnel syndrome;
- increased insulin resistance;
- type 2 diabetes;
- swelling in the arms and legs (edema);
- joint and muscle pain;
- for men, enlargement of breast tissue (gynecomastia);
- increased risk of certain cancers.
HGH treatment is approved in the United States only for the treatment of growth hormone deficiency — and related problems associated with HIV infection. HGH is only effective if administered as an injection.
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