Growth hormone is one of the essential hormones secreted by the anterior pituitary gland of the brain.
As the name indicates, its primary role is to promote the growth of the body.
It is secreted under the influence of hormones secreted by the hypothalamus. The growth hormones releasing hormone (GHRH) stimulates the pituitary to release growth hormone.
While the growth hormone release inhibiting hormone (GHRIH) inhibits the secretion of growth hormone from the pituitary.
This growth hormone secretion is also inhibited by somatostatin, secreted by pancreatic islets.
Physiology of Human Growth Hormone
GH promotes the growth of a person during his early life. It is believed that a person’s height grows until 18 years and ceases to grow after that.
But more specifically on the bone, cartilage, and other cells responsible for body growth in height and overall body mass.
GH increases protein deposition by different mechanisms.
1. It enhances the growth of all the cells and tissues of the body.
During childhood and adolescence, the growth hormone predominantly promotes linear growth through the enhancement of cells and tissues of bone and skeletal muscles.
This includes enlargement of the cell size and increased mitosis and differentiation of bone and muscle cells.
Once adolescence is over, it maintains the mass of cells and tissues of bones and muscles for the rest of life.
It also regulates the metabolism in the organs like the intestine, liver, and pancreas.
It promotes growth and repair, the breakdown of fats, and increases blood glucose levels.
2. It increases the rate of protein synthesis by
a) Enhances the DNA transcription to form mRNA responsible for protein formation.
b) Increase the translocation of RNA for enhanced protein synthesis.
C) Enhanced uptake and transport of amino acids across the cell membrane.
d) Decreases of protein catabolism by mobilization of fatty acids required for gluconeogenesis. Thus amino acids are spared.
3. Increase fat metabolism and thereby lean body mass.
GH promotes the release of fatty acids from adipose tissue. Then it also enhances the utilization of fatty acids for energy generation. Thus, its ability to improve fat metabolism and protein deposition causes lean body mass.
However, it is effective in height growth until age 18. This height growth stops at around 18 due to the development of pubic symphysis.
During this phase, the epiphysis of the long bones unites with the shafts. Once done, no further rise in height is possible.
So growth in height is freely possible till the age of 18 to 19. After that, though the growth hormone is secreted, there is no growth in height. Instead, the body tissue mass grows.
So the best chance of height growth by this hormone is before the end of height growth.
Growth hormone pathway
Stimuli that cause the release of GH
Exercise, Fasting, stress, hypoglycemia, and infusion of arginine stimulate the release of growth hormone.
Growth hormone antagonists
Somatostatin and Octreotide are the agents that can inhibit the secretion of growth hormones by the pituitary.
Of the two, somatostatin is a natural hormone produced in the body. At the same time, Octreotide is a longer-acting synthetic substance.
Can one grow taller after puberty?
Puberty is sexual maturation that occurs around 10-15 years for both girls and boys.
And the body grows in height till the fusion of epiphysis, which is approximately around 18 years.
So one has chances of growth for 4-5years after puberty for a few more years.