Insulin: The Lifesaving Hormone

Estimated reading time: 6 minutes

Insulin is a vital hormone produced by the pancreas, specifically by clusters of cells called the islets of Langerhans. It plays a central role in regulating blood sugar levels and maintaining energy balance in the body. Therefore, understanding insulin and its function is crucial for grasping how the body processes energy and the implications of metabolic disorders like diabetes.

I. What Is Insulin?

Inside the pancreas, the hormone insulin is made in the beta cells, which are part of the islets of Langerhans. Moreover, these islets also contain alpha cells, which produce glucagon, and delta cells. With each meal, beta cells release insulin to help the body use or store the blood glucose (blood sugar) it gets from food. (Insulin Basics for Diabetes – ADA)

Insulin is a peptide hormone composed of 51 amino acids, organized into two chains connected by disulfide bonds. Consequently, it is secreted in response to elevated blood glucose levels, typically after eating. This hormone acts as a key, allowing glucose to enter cells where it can be used as energy or stored for future use.

II. The Role of Insulin in the Body

1. Glucose Regulation: Insulin facilitates the uptake of glucose into cells, particularly in the liver, muscles, and fat tissue, thereby reducing blood sugar levels.
2. Energy Storage: In the liver and muscle cells, insulin promotes the storage of glucose as glycogen. Additionally, in fat cells, it encourages the storage of excess glucose as triglycerides.
3. Protein Synthesis: Insulin supports protein synthesis by promoting amino acid uptake into cells, aiding in muscle growth and repair.
4. Fat Metabolism: Furthermore, it inhibits the breakdown of fats (lipolysis), favoring fat storage during periods of energy surplus.

III. Insulin and Diabetes

Imbalances in insulin production or function are at the core of diabetes:

• Type 1 Diabetes: An autoimmune condition where the immune system attacks insulin-producing cells in the pancreas, leading to little or no insulin production. Consequently, people with Type 1 diabetes require lifelong insulin therapy.
• Type 2 Diabetes: A condition characterized by insulin resistance, where the body’s cells do not respond effectively to insulin. Over time, the pancreas may fail to produce enough insulin to compensate. As a result, Type 2 diabetes is often managed through lifestyle changes, oral medications, and sometimes insulin therapy.
• Gestational Diabetes: A temporary form of diabetes occurring during pregnancy, often linked to insulin resistance.

IV. Types of Insulin

1. Rapid-Acting Insulin: Starts working about 15 minutes after injection, peaks in 1-2 hours, and lasts 2-4 hours. Common types include insulin aspart (NovoLog), insulin glulisine (Apidra), and insulin lispro (Humalog).
2. Short-Acting Insulin: Takes effect within 30 minutes, peaks in 2-3 hours, and lasts about 3-6 hours. Examples include Human Regular (Humulin R, Novolin R).
3. Intermediate-Acting Insulin: Reaches the bloodstream in 2-4 hours, peaks at 4-12 hours, and remains effective for 12-18 hours. Notably, types include NPH (Novolin N).
4. Long-Acting Insulin: Enters the bloodstream several hours after injection and works steadily for up to 24 hours. Examples include degludec (Tresiba), detemir (Levemir), and glargine (Lantus).
5. Ultra Long-Acting Insulin: Begins acting in about 6 hours, has no pronounced peak, and lasts for 36 hours or more. A common type is glargine U-300 (Toujeo).
6. Inhaled Insulin: In 2015, an inhaled insulin product, Afrezza, became available in the U.S. Afrezza is a rapid-acting inhaled insulin administered at the beginning of each meal and can be used by adults with type 1 or type 2 diabetes. Example: Technosphere insulin-inhalation system (Afrezza).

V. Characteristics of Insulin:

1. Onset: The time it takes for insulin to enter the bloodstream and begin lowering blood glucose levels.
2. Peak Time: The period when insulin is most effective at lowering blood glucose levels.
3. Duration: How long insulin continues to lower blood glucose levels.

NCLEX Medications – Endocrine System – Insulin – NCLEX Test Online Review

VI. Insulin Therapy:

Insulin therapy involves the use of synthetic insulin to manage blood sugar levels. Thus, it is available in various forms:

1. Rapid-acting insulin:

Starts working within minutes and is used before meals.

Benefits:

• Quick onset: Starts working within minutes, making it ideal for controlling blood sugar spikes that occur during meals.
• Flexibility: Can be administered just before or even immediately after meals, providing convenience for users with unpredictable meal timings.
• Reduced post-meal hyperglycemia: Effectively manages the rapid rise in blood glucose that follows carbohydrate-rich meals.
• Duration aligns with meal digestion: The short duration of action (2-4 hours) reduces the risk of hypoglycemia after meals compared to longer-acting insulin.

Target patient:

• Patient who need tight post-meal glucose control.
• Situations requiring fast glucose correction.

2. Short-acting insulin:

Effective within 30 minutes, covering meals eaten soon after injection.

Benefits:

• Moderate onset and duration: Effective within 30 minutes and lasts 3-6 hours, providing a slightly longer window for meals compared to rapid-acting insulin.
• Covers meal-related glucose fluctuations: Suitable for managing blood sugar levels for meals eaten soon after injection.
• Reliable and predictable: Often used for structured meal patterns where timing and portions are consistent.

Target patient:

• Patient who have set meal schedules and can plan insulin administration accordingly.
• Use in combination with longer-acting insulin for basal-bolus regimens.

3. Intermediate-acting insulin:

Provides longer blood sugar control, used between meals or overnight.

Benefits:

• Prolonged glucose control: Covers blood sugar needs between meals or overnight, reducing the frequency of injections.
• Steady release: Provides a more consistent insulin supply compared to short-acting insulin.
• Cost-effective: Generally less expensive compared to rapid-acting or long-acting analogs.

Target patient:

• Patient seeking fewer daily injections.
• Baseline glucose management in combination with short-acting insulin for meals.

4. Long-acting insulin:

Offers steady, all-day control.

Benefits:

• Steady all-day control: Mimics the body’s basal insulin production, maintaining stable blood sugar levels for up to 24 hours or more.
• Convenience: Requires only once-daily injections, enhancing compliance and reducing treatment burden.
• Minimal risk of hypoglycemia: No pronounced peak in activity reduces the likelihood of blood sugar drops during fasting periods.
• Compatibility: Often used in combination with rapid-acting insulin for mealtime glucose management.

Target patient:

• Individuals with type 1 or type 2 diabetes requiring consistent baseline insulin.
• Patients prioritizing simplicity and reduced injection frequency.

VII. The Future of Insulin and Diabetes Management:

Advances in technology and research continue to improve insulin therapy and diabetes care. For example, innovations include insulin pumps, continuous glucose monitors (CGMs), and the development of biosynthetic insulin tailored to individual needs. Researchers are also exploring potential cures, such as beta-cell regeneration and islet transplantation.

VIII. Conclusion

Insulin is more than just a hormone; it’s a lifeline for energy balance and metabolic health. While its disruption can lead to significant health challenges like diabetes, advancements in medicine and technology offer hope for better management and, ultimately, a cure. Therefore, understanding and respecting the role of insulin is key to appreciating the intricate harmony of the human body.