Growth hormone, also known as somatotropic hormone (GH, growth hormone), is a protein hormone composed of a sequence of 191 amino acids, that is, molecules aggregated in long chains that serve precisely to form proteins.
Although its primary function is to promote growth, the effect of growth hormone is defined as an "anabolic" complex, that is, stimulating the construction of tissues, organs, and organisms as a whole. This action takes place both directly and through a type, I insulin-like growth factor or somatomedin C, that is, a hormone that acts as an intermediary.
In addition to the effects on statural growth, growth hormone has numerous other effects that have led to its name being changed to "somatotropic hormone" to underline it much more complex systemic action better:
- Protein metabolism.
- Carbohydrate metabolism (carbohydrates).
- Lipid (fat) metabolism.
- Bone / mineral metabolism.
- Water and kidney functions regulation.
The growth hormone is produced by the anterior lobe of the pituitary - the so-called adenohypophysis. It is an endocrine gland that produces hormones located at the base of the skull, placed under the direct control of the hypothalamus.
The hypothalamus regulates growth hormone production by the pituitary through stimulating and inhibitory mediating hormones.
The greatest peaks of growth hormone are found at night, especially with the onset of sleep. These peaks decrease with age, to the point that the growth hormone secretion in adulthood is about 15% of that of puberty.
In addition to sleep, they stimulate the secretion of growth hormone:
- Physical exercise.
- Nutritional status.
The growth hormone acts on specific cellular receptors by stimulating the synthesis of proteins, the demolition of fats (lipolysis), and hindering insulin action. It is also able to determine sodium, potassium, and water retention.
The effects on bone growth are the result of these different actions and the mediation of specific growth factors.
The lack of growth hormone, a condition moreover rare compared to the more frequent forms of short stature, is characterized by a reduced stature growth in children.
Growth hormone deficiency can occur in a highly variable form, and the clinical picture is conditioned by the severity of the hormonal deficit (isolated or associated with that of other pituitary hormones) and by the age of onset.
Most cases of growth hormone deficiency do not recognize an inherited transmission and are not associated with pathological processes of the pituitary or hypothalamus. It is an idiopathic deficit, which is, not related to a well-defined disease.
The deficiency of this hormone can be more rarely congenital, with familiar forms of alterations in the synthesis or function of the growth hormone or receptor for hormones that stimulate its release, or insensitivity of peripheral tissues due to defects in the receptor of the growth hormone or intracellular signal.
The diagnosis of growth hormone deficiency is based on criteria:
- Auxological, such as a statistic deficit associated with reduced growth rate.
- Hormonal, such as the impaired response of growth hormone to stimulus drug tests.
- Possibly neuro-radiological as anomalies of the hypothalamic-pituitary region.
However, it should be borne in mind that the insufficient response to stimulus tests, in the presence of normal auxological and clinical findings, does not prove by itself the presence of a growth hormone deficiency.
The diagnosis involves assessing the pituitary growth hormone reserve in those boys and girls with a clinical history and physical examination compatible with a deficiency of this hormone.
So - in the absence of systemic, endocrine, nutritional, or chromosomal diseases:
- Stature less than the 3rd centile using growth cards.
- Bone age delay.
- Low levels of insulin-like growth factors.
- Stature growth rate lower than the 25th centile.
A growth hormone peak below a certain threshold (8 ng / ml) at two different stimulation tests, performed on two different days, allows the diagnosis of growth hormone deficiency.
The diagnosis is made by the reference centers, identified by the individual regions, according to well-standardized criteria.
In every child diagnosed with a growth hormone deficiency, before starting treatment, magnetic resonance imaging of the brain is indicated, paying particular attention to the hypothalamic-pituitary region.
The replacement therapy with growth hormone, a "photocopy" of the natural product obtained from the pituitary through DNA, is able to significantly improve the final height of children with a deficiency of this hormone.
The dose of the drug is distributed in daily administrations, preferably in the evening, to mimic the normal production of growth hormone.
The injections are made with ready-to-use syringes, with special pens or with subcutaneous needle-free devices, which are easy to use even for the child who can, therefore, self-administer the drug, always under the supervision of an adult.
The treatment, which must be carefully monitored, produces a significant increase in the rate of growth of the state, and can allow the achievement of normal stature.
In addition to the effect on statural growth, the therapy improves body composition (increase in lean mass at the expense of fat) and lipid structure, thus reducing cardiovascular risk, improves bone mineralization, and significantly affects psychophysical well-being.
Replacement treatment is indicated only in those children with short stature in whom a growth hormone deficiency has been properly documented.
The treatment of the deficit should start as early as possible, as it allows preventing the establishment of an important statutory gap. The higher the age of the child, the shorter the time available for treatment as the opening of the growth cartilages is reduced.
The treatment is continued until an acceptable height is reached or in the face of a significant slowdown in the rate of growth (which coincides with the sealing of the growth cartilages).
In the most serious cases of deficiency, the replacement treatment must instead be prolonged for life, given the important metabolic effects controlled by the hormone beyond the growth of the state.
When the child actually has a proven growth hormone deficiency, the dosages are adequate and monitored periodically; the side effects are few, almost always transient and solvable.
Therefore, the use of the hormone under these conditions is considered safe. Undoubtedly, children undergoing growth hormone treatment must be followed periodically by the appropriate reference centers, such as Auxologico, and for a few periods, even after the suspension of therapy.
Feb 04, 2020