Human growth hormone (HGH), also called somatotropin, is a 191-amino acid polypeptide hormone naturally produced by the pituitary gland. HGH plays a major role in stimulating growth, cell reproduction, and tissue regeneration. While known for promoting linear growth in children, HGH also regulates metabolism by influencing how the body uses fat and sugar for energy. Therapeutic application for hormone deficiency requires a large, consistent, and safe supply of this active compound.
The Necessity of Synthetic Production
The earliest therapeutic use of HGH, beginning in the 1950s, relied on an unsustainable and hazardous sourcing method. HGH was extracted and purified directly from the pituitary glands of human cadavers post-mortem, resulting in pituitary-derived human growth hormone (p-hGH). This process had inherent limitations, including low yield and dependence on donor tissue, making large-scale production impossible.
A more serious concern arose in the mid-1980s when some batches of p-hGH were found contaminated with prions, the infectious agents responsible for Creutzfeldt-Jakob disease (CJD). CJD is a fatal neurodegenerative disorder. This severe health risk led to the immediate termination of the cadaveric HGH program in 1985, creating an urgent need for a safe, non-human-derived alternative.
Large-Scale Manufacturing Through Recombinant Technology
The solution to the safety and supply crisis was the development of a synthetic version, known as somatropin, using recombinant DNA technology. This process begins by isolating the human gene that contains the instructions for manufacturing the HGH protein. The isolated gene is then inserted into a small, circular piece of DNA called a plasmid, which transfers the genetic material.
This engineered plasmid is introduced into a host microorganism, typically Escherichia coli or certain yeast strains. The host cells, now containing the human HGH gene, are grown in massive bioreactors during fermentation. As the host cells multiply, they follow the instructions in the inserted gene, producing large quantities of the identical human growth hormone protein.
Following fermentation, the synthetic HGH must be separated from the host organisms through an extensive purification process. Techniques like affinity chromatography are employed to isolate the pure somatropin molecule. This advanced method ensures the therapeutic product is structurally nearly identical to the natural hormone and is completely free from human-derived contaminants like prions.
Approved Therapeutic Applications
Somatropin is a prescription medication approved for treating a specific range of medical conditions in both children and adults. In pediatric patients, the primary indication is for growth failure resulting from inadequate secretion of endogenous growth hormone (GHD). Somatropin is also used to promote growth in children with specific genetic syndromes or conditions that cause short stature.
The pediatric conditions treated include:
- Turner Syndrome
- Prader-Willi Syndrome
- Chronic kidney disease
- Noonan syndrome
- Short stature in children born small for gestational age who fail to show catch-up growth
For adults, the approved use is restricted to the treatment of Adult Growth Hormone Deficiency. This deficiency may be a continuation of childhood GHD or a new condition resulting from pituitary disease, surgery, or radiation. Somatropin may also be prescribed to treat wasting (cachexia) in patients with Human Immunodeficiency Virus (HIV). The medication is administered via daily subcutaneous injection, and ongoing medical monitoring is required to assess response and adjust dosing.