Functions of Growth Hormone

Growth hormone is secreted by the pituitary gland during REM sleep. Its functions are

  • Maintenance of bones, joints, muscle and connective tissue;
  • In frail elderly, it will improve lean muscle mass, bone density and improve stamina
  • It has significant effects on the brain:- receptors are located in the hippocampus – which is an important site for short term and working memory: supplementation in adults suffering from growth hormone deficiency improves mood, alertness, motivation, , memory, and general cognitive function
  • It has been shown to reverse osteoporosis and speed recovery from hip fracture;
  • It is also beneficial in the treatment of refractory heart failure, and has been shown to improve arteriosclerosis and decrease LDL cholesterol, triglycerides and CRP ( an index of inflammation associated with increased of heart disease);
  • It is important for immune function –and will reverse age-related decline in the production of  T and B–cell lymphocytes
  • It acts synergistically with testosterone and DHEA in improving lean muscle mass, decreasing abdominal fat up to 50%, and increasing VO2 max (aerobic capacity)

Growth hormone production declines with age from the mid 30”s – reaching about 50% maximum by age 50, and declining by 50% every 7 years after that. Growth hormone deficiency is the major factor behind frailty syndrome (frail older people with brittle bones and mobility problems)

Diagnosis of Adult Growth Hormone deficiency

Classic diagnosis is by the insulin stress test or by IV administration of Arginine and GHRH, followed by sequential blood tests to observe for the absence of the expected normal rise in growth hormone levels; there is some movement towards favouring blood or urine IGF1 levels (IGF1 being the immediate metabolite of GH) or IGFBP-6 (a metabolite which has a longer half –life)-as an acceptable alternative.

Growth Hormone Replacement Therapy

However, Growth Hormone replacement therapy is very controversial. Besides official sanctioning of enhanced athletic performance in professional athletes who are illegally taking supplements, there are concerns about the potential for increased insulin resistance, potential to fuel the growth of pre-existent cancer, and hypothetical adverse effects on heart muscle and bones. However, multiple articles in respected medical journals eg the New England Journal of Medicine, Journal of Endocrinology and Metabolism - cite the lack of evidence that Growth Hormone replacement causes heart disease or cancer; while gigantism (abnormal growth of long bones) and cardiomyopathy have classically been associated with growth hormone producing pituitary tumours, not with supplementation under medical supervision.

Practical issues with Recombinant HGH Replacement therapy

Observed side-effects with recombinant HGH administration have been carpal tunnel syndrome, arthralgia, and insulin resistance. Due to the controversy surrounding GH supplementation for adults, we will not prescribe it without prior consultation and testing by an endocrinologist.

Alternatives to HGH Replacement Therapy

Secretagogues, Sermorelin, GHRP-6

These are amino acid complexes that stimulate secretion of Growth Hormone; oral arginine has been shown to be relatively ineffective due to inactivation by gastric acid; but Secretropin administered sublingually exhibits some promise as evidenced by elevation of IGF1 levels in an initial small study.

Other substances that may be of benefit in elevating GH secretion are Sermorelin acetate ( GH releasing factor) administered by S/C injection and GHRP-6 (growth hormone releasing peptide -6), also administered by S/C injection. These are usually used in conjunction with DHEA and /or testosterone, if indicated by demonstrable deficiency on testing.