Growth hormone (GH) primarily functions to influence metabolism by adjusting the body's use of fats, carbohydrates, and proteins.
Metabolic Actions of Growth Hormone
Growth hormone's metabolic actions are not immediate; they unfold over time. Here's a breakdown of key metabolic functions:
Acute Actions (2-3 hours post-release):
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Stimulates Lipolysis: GH encourages the breakdown of fats (lipolysis), releasing fatty acids into the bloodstream. This provides the body with an alternative energy source.
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Promotes Ketogenesis: As a result of increased fatty acid availability, GH enhances ketogenesis, the process of producing ketones by the liver. Ketones can be used as an energy source, particularly during fasting or low carbohydrate intake.
- Practical Insight: These actions help the body adapt to fasting and stress by providing the body with energy when glucose is less available.
Effects on Insulin Sensitivity:
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Decreases Insulin Sensitivity: GH reduces the body's response to insulin in the liver and muscle. This means that these tissues become less efficient at taking up glucose from the bloodstream.
- Example: A drop in insulin sensitivity increases blood glucose levels, ensuring sufficient glucose availability for the brain.
Summary of Metabolic Functions:
| Function | Description |
|---|---|
| Lipolysis | Breakdown of fats, releasing fatty acids for energy. |
| Ketogenesis | Production of ketones, an alternative fuel source, by the liver. |
| Insulin Sensitivity | Decreased response to insulin in the liver and muscle, leading to reduced glucose uptake by these tissues. |
In essence, growth hormone plays a crucial role in managing energy availability by mobilizing fat stores and modulating glucose utilization. This becomes particularly important in situations of stress or fasting, as indicated by the reference: "Growth hormone (GH) has acute actions to stimulate lipolysis and ketogenesis after 2 to 3 hours, effects that may be important in the adaptation to stress and fasting. This is accompanied by a decrease in insulin sensitivity in both liver and muscle."
