ADENO-HIPÓFISE: HORMÔNIO DO CRESCIMENTO (GH) | MK Fisiologia

Summary

In this video, the host delves into the role of Growth Hormone (GH) produced by the pituitary gland. GH stimulates growth through both hypertrophy and hyperplasia, affecting nearly every cell in the body. It also stimulates the liver to release Insulin-like Growth Factor 1 (IGF-1), which is essential for bone growth. GH plays a key role in metabolism by increasing blood glucose levels, opposing insulin’s actions, and promoting fat breakdown. The secretion of GH is regulated by hypothalamic hormones and influenced by factors like sleep, exercise, and stress. The video emphasizes GH’s complex regulation and its vital role in development and metabolism.

Takeaways

• 😀 GH (Growth Hormone) is produced by somatotroph cells in the pituitary gland, and it plays a crucial role in growth and metabolism.
• 😀 The GH hormone is a protein and is stored in vesicles until a signal from the hypothalamus triggers its release into the bloodstream.
• 😀 Approximately 40% of circulating GH binds to a transport protein called GHBP, which prolongs its half-life to about 20 minutes.
• 😀 GH affects nearly all cells in the body, stimulating growth through hypertrophy (cell size increase) and hyperplasia (cell multiplication).
• 😀 GH also stimulates the liver to produce IGF-1 (Insulin-like Growth Factor 1), which is essential for bone growth and cellular growth.
• 😀 IGF-1 is primarily produced in the liver and has a longer half-life (around 20 hours) compared to GH, being bound to a specific transport protein called IGFBP.
• 😀 IGF-1, like GH, promotes growth by activating receptors on almost all cells in the body, encouraging hypertrophy and hyperplasia.
• 😀 The growth of long bones, especially during childhood and puberty, is influenced by GH, which stimulates local IGF-1 production in bone cells.
• 😀 GH has metabolic effects that oppose those of insulin, such as promoting lipolysis (fat breakdown), increasing glucose levels, and reducing glucose uptake in muscles and adipose tissue.
• 😀 GH secretion is regulated by the hypothalamus, with the release of GHRH (GH-releasing hormone) stimulating GH production, and somatostatin inhibiting it.
• 😀 Stress, physical exercise, and fasting can stimulate GH release, while psychological stress may inhibit it, leading to growth issues in individuals with early-life trauma.

Q & A

What is the role of growth hormone (GH) in the body?

Growth hormone (GH) plays a crucial role in promoting growth and development in the body. It stimulates cellular growth through hypertrophy (increase in cell size) and hyperplasia (increase in cell number). GH also contributes to protein synthesis and impacts metabolism, particularly in regulating glucose and fat metabolism.

How does growth hormone (GH) influence the metabolism of fats?

GH stimulates lipolysis, which is the breakdown of fats (triglycerides) into fatty acids and glycerol. These products are then released into the bloodstream, with fatty acids serving as an energy source in muscles and glycerol being used in gluconeogenesis (the production of glucose) in the liver.

What is the function of insulin-like growth factor 1 (IGF-1) in the body?

IGF-1 is a hormone stimulated by GH that acts as a key mediator of GH’s growth-promoting effects. It plays an essential role in bone growth, especially during childhood and puberty, by stimulating cartilage formation and conversion into bone in the growth plates of long bones.

How does GH interact with the liver and influence IGF-1 production?

GH binds to specific receptors in liver cells, stimulating the synthesis and secretion of IGF-1. This process is important because IGF-1, produced by the liver, supports GH’s indirect effects on growth in various tissues throughout the body.

What is the impact of GH on glucose metabolism?

GH increases blood glucose levels by promoting gluconeogenesis in the liver, which generates glucose from non-carbohydrate sources. Additionally, GH reduces glucose uptake by muscle and adipose tissues, further increasing glucose availability in the bloodstream.

How does GH secretion vary throughout the day?

GH secretion follows a pulsatile pattern that is regulated by the circadian rhythm. There are peaks in secretion during deep sleep, particularly during slow-wave sleep, aligning with the body's sleep-wake cycle. This rhythmic release ensures effective growth and metabolic regulation.

What are the effects of exercise on GH secretion?

Exercise stimulates the secretion of GH, particularly during intense physical activity. This response supports tissue growth and repair, as well as enhancing metabolism by promoting fat breakdown and increasing glucose availability.

What is the role of GHRH and somatostatin in the regulation of GH secretion?

GHRH (Growth Hormone Releasing Hormone) stimulates the secretion of GH from the pituitary, while somatostatin inhibits its release. These hormones are produced by the hypothalamus and work together to maintain GH levels within a balanced range.

How does GH affect bone growth during childhood and puberty?

During childhood and puberty, GH stimulates bone growth by acting on the epiphyseal plates (growth plates) of long bones. GH promotes the production of IGF-1 in these areas, which in turn stimulates the formation of cartilage and its conversion into bone, leading to the lengthening of bones.

What happens when GH levels are too high or too low?

Excessive GH can lead to conditions like gigantism or acromegaly, where excessive growth occurs, particularly in bones and tissues. Conversely, GH deficiency can lead to stunted growth in children or metabolic issues in adults. The body regulates GH levels through negative feedback mechanisms involving GH itself and IGF-1.