Released into blood stream every morning in decreasing amounts over age. The hormon is double the size of insulin and taken orally has no effect, except that the saliva can absorb about 5% of it.
The growth hormone deficiency that is commonly associated with hypopituitarism causes pituitary dwarfism.
Growth hormone was previously taken from pigs, is now produced in the slightly different human form using genetic engineering.
hGH taken at higher age is said to cause loss of weight, improvement of memory, of sex drive, and of general motivation. Many products offer so called oral hGH, that is absorbed by saliva. Other products must be injected.
Researchers are working on the related hormone growth hormone-releasing hormone (GHRH), which triggers production of the HGH, that hopefully can be taken orally.