GROWTH HORMONE (GH)

Mauro Czepielewski, MD., Ph.D. in Endocrinology – São Paulo State University School of Medicine (UNIFESP). Vice-Director of the State University Rio Grande do Sul School of Medicine (UFRGS). Associate Professor – Internal Medicine Department/UFRGS.

What is it?

It's a hormone available in every normal people, which is produced by the hypophysis gland, located at the base of the skull. Its structure of amino-acids has been known for over 40 years, and over 10 years ago it was synthesized by means of transgenic techniques, being available for use in several situations.

What's its function in the organism?

It's important for growth from the early years until the closure of the growth cartilage of the bones (epiphysis), which takes place at the end of puberty, usually between the ages of 15 and 20.

It also plays important roles in metabolism, especially:
 

increase in protein synthesis (mainly in the bones and muscles)
decreases fat deposition in some regions of the organism such as abdomen and trunk
increases the need of insulin by the organism
retains sodium and electrolytes
increases bowel absorption and renal elimination of calcium

Normal release occurs during normal sleep, with 3 or 4 peaks every night. These peaks are higher at puberty and tend to drop off with aging in all individuals.

The control of GH secretion by the hypophysis is regulated by a brain region called hypothalamus, which produces 2 hormones. One of them is the GHRH (GH-releasing hormone), which stimulates its release, the other is the inhibitor, called somatostatin.

It acts directly on some tissues, chiefly via the production of growth factors, especially an insulin-like factor called IGF-1 (insulin growth factor 1).

What does one feel when there's deficit or excess of GH?

GH deficit causes a disorder called hypopituitarism, while the excess leads to acromegaly, both described in specific items on this site.

When is GH treatment indicated?

GH hormone replacement treatment is indicated in the following situations:
 

when its deficiency is demonstrated (hypopituitarism), that is:

Short stature or nanism from a hypophysial cause (hypopituitarism), usually associated to the replacement of other hormones also deficient. Adult hypopituitarism or adult GH deficiency, normally resulting from a hypophysial disorder or following hypophysis radiotherapy and/or surgery.

in diseases in which its replacement may cause beneficial effects on growth:

Turner's syndrome: short stature in girls associated to developmental collapse in puberty, and changes in several parts of the organism caused by the lack or anomaly of one of the x chromosomes (karyotype 46 x0). Children and adolescents having chronic renal failure, associated to the management of renal disease and several supporting treatments. Some genetic conditions in which bone formation defects occur (bone dysplasia), being indicated in these cases only for some specific disorders, and care must be taken so as to prevent greater disproportion between the different parts of the body (upper and lower limbs, thorax and abdomen).

It's important to point out that, for GH replacement, only the synthetic hormone must be used.

The human hormone, obtained from cadaver hypophysis, mustn't be employed due to the risk of contamination with several severe diseases. The use of hormones extracted off animals is also completely contraindicated, not only due to the contamination risk, but also the allergic reaction that may result in view of the different molecular structure of animal hormone.

Current and relevant questions about GH
 

In adult patients with GH deficit, its replacement enhances physical ability, trims down bodyweight, redistribute abdominal fat, increases muscle mass, improves mood and intellectual performance, among other important effects.
In view of these excellent beneficial effects, its use began to be speculated for conditions such as severe obesity, and, mainly, with the purpose to reduce the aging process and improve physical conditioning.
These applications, however, are not scientifically recommended; much to the contrary, they're even contraindicated. Therefore, in sports in general, its utilization is regarded as illegal, being included among the substances prohibited by the International Olympic Committee.
As regards its anti-aging effect, this hasn't been demonstrated yet. On the contrary, in normal elder people, there's a progressive reduction of GH production, this process being considered associated to aging. Associated chronic diseases, nutritional changes, reduction of physical activity, altered sleep and use of several medications are situations in which hormone production may worsen. The application of GH in the elder can bring about severe side effects, such as triggering diabetes mellitus, increase in arterial pressure, aggravation of joint pain and arthrosis, swellings (edemas) and worsening the cardiac and renal functions.
Depending on the dose applied, signs and symptoms similar to acromegaly may appear, as described in the article "Acromegaly" on this site.
Share →