Physiology of Growth Hormone

What does GH stand for?

What is the primary function of growth hormone?

Growth hormone is an anabolic hormone.

What two feedback loops control the release of growth hormone?

What is the primary effect of growth hormone on bone and cartilage?

Growth hormone can promote the growth of skeletal tissue after epiphyseal closure.

What is the condition that arises when growth hormone levels are excessively high?

What is the condition that results from excessive growth hormone production in adulthood?

Excessive growth hormone production leads to decreased insulin sensitivity.

What term describes the condition where growth hormone decreases carbohydrate utilization?

How does growth hormone affect fat metabolism?

Which of the following is NOT a characteristic of growth hormone?

Growth hormone is a peptide hormone.

Where is growth hormone produced?

Growth hormone release is primarily regulated by the short loop feedback control system.

What type of cells secrete growth hormone?

Growth Hormone (Somatotropin)

Originates from somatotrophic acidophilic cells
Short-loop feedback control by pituitary hormones is always inhibitory
Ultra-short feedback control by releasing hormones on themselves is autocrine

Physiological Functions of Growth Hormone

A- Effect on Protein Metabolism

Anabolic hormone
Increases protein synthesis throughout the body
Increases cell size (hypertrophy) and number (hyperplasia)
Achieved by:
- Increasing amino acid transport through cell membranes
- Enhancing mRNA translation
- Increasing DNA to mRNA transcription
- Decreasing protein catabolism (using fatty acids for energy instead of proteins)

B- Effect of Growth Hormone on Growth

Increases protein synthesis, cell division, and proliferation
Stimulates growth of all soft tissues and erythropoiesis (blood cell production)
Produces positive nitrogen balance
Stimulates cartilaginous growth at epiphyses (ends of bones) indirectly through somatomedins (like IGF-1, also known as somatomedin C)

Somatomedin C Effect on Skeletal Growth

Increases protein deposition by chondrocytes and osteoblasts
Increases the rate of chondrocyte and osteoblast reproduction
Converts chondrocytes into osteoblasts forming bone
Stimulates osteoblasts, causing bone deposition
Thickens bone and increases total bone mass, even after epiphyseal closure

Other Effects

Carbohydrate Metabolism: Decreases carbohydrate utilization in peripheral tissues during periods of fasting, exercise, or stress. Increases glucose production in the liver.
Fat Metabolism: Lipolytic and ketogenic; enhances fat utilization and increases free fatty acid levels during periods of fasting, exercise, or stress. Excessive GH can lead to the production of ketones and acetoacetic acid, potentially causing ketosis.
Insulin Resistance: Excessive GH can decrease insulin receptor affinity, leading to hyperglycemia, hyperlipidemia, and impaired insulin action, known as insulin resistance.

Explore the essential roles of growth hormone (somatotropin) in protein metabolism and growth. This quiz covers the hormone's effects on cell size, division, and its anabolic properties. Discover how growth hormone is involved in stimulating tissue growth and maintaining a positive nitrogen balance.