Growth hormone

**Biochemistry and Regulation of Growth Hormone**:
– Genes for human growth hormone are located on chromosome 17.
– GH secretion in the pituitary is regulated by the hypothalamus.
– GH release is influenced by physiological stimulators like exercise and nutrition.
– GH receptor interaction involves four helices.
– GH isoforms are released into the blood, including a variant of approximately 20 kDa.
– GH isoforms circulate partially bound to a protein called GHBP.
– GH secretion peaks occur during sleep stages and throughout the day.
– GH release is primarily determined by the balance of GHRH and GHIH.
– GH is synthesized and secreted by somatotropic cells in a pulsatile manner.
– Factors like age, sex, diet, exercise, and stress affect GH secretion.

**Structural Characteristics of Growth Hormone**:
– The major isoform of human growth hormone is a protein of 191 amino acids.
– GH isoforms exist in the pituitary gland, including a 20 kDa variant.
– GH isoforms partially bind to a protein called GHBP.
– Variants of GH exist in the pituitary gland, including a 20 kDa variant.
– GH has a molecular weight of 22,124 daltons.
– GH is evolutionarily homologous to prolactin and chorionic somatomammotropin.
– GH variants, including a 20 kDa variant, circulate in the blood.
– An additional variant of ~ 23-24 kDa has been reported in post-exercise states.

**Clinical Applications and Effects of Growth Hormone**:
– GH stimulates increased height during childhood through mechanisms involving chondrocytes and IGF-1 production.
– GH has a short biological half-life of about 10 to 20 minutes.
– GH stimulates the production of IGF-1 in the liver, promoting growth in various tissues.
– GH deficiency can result in growth failure, short stature, and weaker bones.
– GH replacement therapy is used to treat GH deficiency and can improve body composition, bone density, and psychosocial well-being.
– GH plays a crucial role in mental and emotional well-being, with potential benefits in cognitive function.
– GH has been studied for its impact on treating depression.
– GH replacement therapy in adults with GH deficiency results in reduced fat mass, increased lean mass, improved bone density, and better lipid profile.

**Medical and Performance-Related Aspects of Growth Hormone**:
– GH replacement therapy is used in adults with GH deficiency.
– Long-acting growth hormone analogues are available for weekly injections.
– GH is used to treat conditions causing short stature and muscle wasting due to AIDS.
– GH has been used by athletes in various sports to enhance athletic performance.
– GH doping is difficult to detect due to its endogenous nature.
– GH is legally available only by prescription in the US.
– Companies sell products linked to GH as HGH Releasers in dietary supplements.

**Regulatory and Agricultural Considerations**:
– GH has been incorrectly associated with anabolic sex hormones in the European beef hormone controversy.
– It is illegal for dietary supplements to contain GH in the US.
– Legal to give bovine GH to dairy cows in the US to increase milk production.
– Legal to use GH in raising cows for beef in the US.
– Illegal to use GH in poultry farming in the US.
– Attempts to approve porcine somatotropin for pigs in the US have been withdrawn.
– Genentech pioneered recombinant human growth hormone therapy approved by the FDA in 1985.