Insulin-like growth factor (IGF-1) - Somatomedin C - GH- Dwarfism, Gigantism, Acromegaly - Endocrine

Summary

In this video, Medicosis Perfectus explains the roles of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) in human physiology. GH, secreted by the anterior pituitary, stimulates IGF-1 production in the liver, which mediates growth by promoting protein synthesis and cell growth. The video discusses various conditions related to GH and IGF-1, including acromegaly, hypopituitarism, acondroplasia, and different types of dwarfism. It highlights the distinct mechanisms through which these hormones operate and their clinical implications, emphasizing the complexity of the endocrine system in regulating growth.

Takeaways

• 😀 Growth hormone (GH) stimulates the production of insulin-like growth factor 1 (IGF-1) in the liver, which plays a crucial role in growth and development.
• 😀 IGF-1 acts as a mediator for GH, promoting anabolic processes in muscle, bone, and cartilage growth.
• 😀 The half-life of IGF-1 is about 20 hours, significantly longer than GH's half-life of less than 20 minutes, which enhances its effects on growth.
• 😀 GH is secreted by the anterior pituitary gland and its release is regulated by the hypothalamus through growth hormone-releasing hormone (GHRH) and somatostatin.
• 😀 IGF-1 helps increase amino acid uptake and protein synthesis, facilitating muscle and tissue growth.
• 😀 The mechanisms of GH and IGF-1 differ; GH operates via the JAK-STAT pathway, while IGF-1 works through receptor tyrosine kinases, similar to insulin.
• 😀 Conditions such as acromegaly involve elevated levels of GH and IGF-1, while hypopituitarism results in low levels of both hormones.
• 😀 Diagnostic tests, such as the arginine stimulation test, can help assess GH and IGF-1 levels to identify pituitary disorders.
• 😀 Genetic disorders like achondroplasia and Levi dwarfism illustrate the impact of IGF-1 production and receptor sensitivity on growth.
• 😀 Understanding the interplay between GH and IGF-1 is essential for comprehending growth regulation and related disorders in human physiology.

Q & A

What is IGF-1, and what role does it play in the body?

IGF-1, or insulin-like growth factor 1, is a polypeptide that acts as a mediator for growth hormone. It is produced primarily in the liver and plays a crucial role in promoting growth by stimulating protein synthesis and aiding in the development of muscles, cartilage, and bones.

How does growth hormone affect IGF-1 production?

Growth hormone stimulates the liver to produce IGF-1. When growth hormone is released into the bloodstream, it prompts liver cells to secrete IGF-1, which in turn promotes growth and development in various tissues.

What happens when growth hormone is injected into cartilage outside the body?

When growth hormone is injected into cartilage outside the body, there is no significant growth. This is because the necessary middleman, IGF-1, is not produced in that setting, unlike when growth hormone is released in the body where IGF-1 is synthesized.

What are the half-lives of growth hormone and IGF-1?

The half-life of growth hormone is less than 20 minutes, while the half-life of IGF-1 is approximately 20 hours. This difference is due to IGF-1 being strongly bound to plasma proteins, allowing it to remain active in the bloodstream longer.

What conditions can result from low levels of IGF-1?

Low levels of IGF-1 can lead to conditions such as hypopituitarism, where the pituitary gland does not secrete enough growth hormone, and growth hormone insensitivity syndromes like Laron dwarfism, where the body cannot utilize growth hormone effectively.

How do growth hormone and IGF-1 differ in their mechanisms of action?

Growth hormone works via the JAK-STAT pathway, which does not involve receptor tyrosine kinases, while IGF-1 functions similarly to insulin, binding to its receptor and utilizing receptor tyrosine kinases to facilitate its effects on growth and metabolism.

What is the clinical significance of measuring IGF-1 levels?

Measuring IGF-1 levels is clinically significant for diagnosing growth hormone deficiencies or excesses, as IGF-1 reflects the integrated effects of growth hormone over time and is more stable than measuring growth hormone levels directly.

What is acromegaly, and how is it related to IGF-1?

Acromegaly is a condition characterized by excess growth hormone, usually due to a pituitary tumor. It leads to increased levels of IGF-1, which results in abnormal growth of bones and tissues, particularly in the hands, feet, and face.

What role does somatostatin play in the regulation of growth hormone?

Somatostatin is a hormone that inhibits the release of growth hormone from the anterior pituitary gland. It acts as a universal inhibitor, decreasing growth hormone secretion when levels are adequate.

How does the body respond to arginine administration in the context of growth hormone secretion?

Administering arginine typically stimulates the pituitary gland to release growth hormone, leading to an increase in IGF-1 levels. However, if the pituitary is dysfunctional, this stimulation may not occur, indicating a potential hormonal deficiency.