Growth hormone (GH) is involved in controlling people's general health and an underproduction of growth hormone (growth hormone deficiency or GHD) leads to people feeling generally unwell and having a lower feeling of well-being and quality of life scores. In addition, the investigators, and others, have demonstrated people with GHD have reduced muscle and bone strength and a greater storage of fat, particularly in unfavourable sites such as in the liver and within the abdomen (visceral fat), rather than beneath the skin (subcutaneous fat).
Treatment of GHD is achieved by administration of GH replacement therapy, given as a once daily subcutaneous injection, which generally reverses these symptoms. Due to its high cost, patients are only started on GH replacement depending on the impact that the GHD is having on their quality of life. Patients must be severely affected to be eligible for replacement therapy. Patients are screened for quality of life using a well validated, disease specific questionnaire (AGHDA, Adult Growth hormone deficiency questionnaire) and there are specific criteria that govern whether a patient with GHD warrants GH replacement and also whether they continue treatment (NICE guideline: Growth hormone deficiency (adults) - human growth hormone (TA64)).
This study will specifically determine whether the mechanism of action by which GH exerts its beneficial effects on metabolism (within adipose tissue and skeletal muscle) involves changes in serum FGF21 concentrations.