Insulin and Growth Hormone

Insulin and growth hormone are both important hormones involved in various physiological processes in the body. However, they differ in their mechanisms of action and the effects they have on different tissues.

Insulin:

- Insulin is a peptide hormone produced by the beta cells of the pancreas. Its primary role is to regulate blood glucose levels by promoting the uptake, utilization, and storage of glucose in various tissues.
- Insulin stimulates the uptake of glucose into cells, particularly muscle and adipose tissue, by increasing the translocation of glucose transporters (GLUT4) to the cell membrane. This allows for the entry of glucose into the cells, where it can be used for energy or stored as glycogen.
- In addition to its role in glucose metabolism, insulin also affects lipid metabolism. It inhibits the breakdown of stored fats (lipolysis) by inhibiting hormone-sensitive lipase (HSL) in adipose tissue. This means that insulin reduces the release of fatty acids from fat cells, promoting fat storage.
- Insulin also stimulates lipoprotein lipase (LPL) activity in adipose tissue. LPL is an enzyme that breaks down triglycerides in lipoproteins, such as chylomicrons and very low-density lipoproteins (VLDL), releasing fatty acids for storage in adipose tissue.

Growth Hormone:

- Growth hormone (GH), also known as somatotropin, is a peptide hormone produced by the anterior pituitary gland. Its primary role is to promote growth and development, particularly during childhood and adolescence.
- GH stimulates the release of insulin-like growth factors (IGFs) from the liver and other tissues. IGFs, particularly IGF-1, mediate the effects of GH on various tissues and play a crucial role in promoting growth and development.
- In muscle tissue, GH enhances the transport of amino acids across cell membranes, increasing protein synthesis and promoting muscle growth. It also stimulates the proliferation and differentiation of muscle cells.
- GH has indirect effects on fat metabolism. It promotes lipolysis in adipose tissue, leading to the release of fatty acids into the bloodstream for use as an energy source. GH also reduces the uptake and storage of glucose in adipose tissue, which helps to spare glucose for other tissues, such as the brain.

Conclusion:

In summary, insulin and growth hormone have distinct roles and effects on different tissues. Insulin primarily regulates glucose metabolism and promotes fat storage, while growth hormone promotes growth and development, enhances protein synthesis in muscles, and promotes fat utilization. The correct answer to the given question is option D, as insulin stimulates hormone-sensitive lipase in fat cells, promoting fat storage.