2013-05-14

Hunting For Clues

Here are some excerpts from the Wikipedia article on human growth hormone. All emphases are mine; bold text is used for emphasis, while bold highlighted text is a major emphasis. I have also added comments to the excerpts.

On the function of HGH:
In addition to increasing height in children and adolescents, growth hormone has many other effects on the body:
  • Stimulates the growth of all internal organs excluding the brain
On the secretion of HGH in general:
Secretion of growth hormone (GH) in the pituitary is regulated by the neurosecretory nuclei of the hypothalamus. These cells release the peptides Growth hormone-releasing hormone (GHRH orsomatocrinin) and Growth hormone-inhibiting hormone (GHIH or somatostatin) into the hypophyseal portal venous blood surrounding the pituitary. GH release in the pituitary is primarily determined by the balance of these two peptides, which in turn is affected by many physiological stimulators (e.g., exercise, nutrition, sleep) and inhibitors (e.g., free fatty acids) of GH secretion.
Stimulators and inhibitors of HGH:
A number of factors are known to affect GH secretion, such as age, gender, diet, exercise, stress, and other hormones.[1] Young adolescents secrete GH at the rate of about 700 μg/day, while healthy adults secrete GH at the rate of about 400 μg/day.[16] Sleep deprivation generally supresses GH release, particularly after early adulthood.[17] 
Stimulators of growth hormone (GH) secretion include:
  • peptide hormones
    • GHRH (somatocrinin) through binding to the growth hormone-releasing hormone receptor (GHRHR)[18]
    • ghrelin through binding to growth hormone secretagogue receptors (GHSR)[19]
    • increased androgen secretion during puberty (in males from testis and in females from adrenal cortex)
Inhibitors of GH secretion include:
Sidenote, from the article on Insulin-like Growth Factor 1 as a therapeutic agent:
Several companies have evaluated IGF-1 in clinical trials for a variety of additional indications, including type 1 diabetestype 2 diabetesamyotrophic lateral sclerosis (ALS aka "Lou Gehrig's Disease"),[26] severe burn injury and myotonic muscular dystrophy (MMD). Results of clinical trials evaluating the efficacy of IGF-1 in type 1 diabetes and type 2 diabetes showed great promise in reducing hemoglobin A1C levels, as well as daily insulin consumption. However, the sponsor, Genentech, discontinued the program due to an exacerbation of diabetic retinopathy[27] in patients coupled with a shift in corporate focus towards oncology.
Back to the HGH article, on clinically relevant excess levels of HGH:
Prolonged GH excess thickens the bones of the jaw, fingers and toes. Resulting heaviness of the jaw and increased size of digits is referred to as acromegaly. Accompanying problems can include sweating, pressure on nerves (e.g., carpal tunnel syndrome), muscle weakness, excess sex hormone-binding globulin (SHBG), insulin resistance or even a rare form of type 2 diabetes, and reduced sexual function.
The article also notes side-effects of therapeutic HGH treatment: "More rarely, patients can experience joint swelling, joint pain, carpal tunnel syndrome, and an increased risk of diabetes.[36] In some cases, the patient can produce an immune response against GH."