Insulin is produced by the:

Insulin is a vital hormone responsible for regulating blood glucose levels. It is produced by the **pancreas**, specifically within specialized clusters of cells known as the **Islets of Langerhans**. Inside these islets, the **beta cells** synthesize and secrete insulin into the bloodstream when glucose levels rise (e.g., after a meal). Let's evaluate the other options: 1. **Thyroid**: Produces hormones like thyroxine ($T_4$) which regulate metabolism. 2. **Liver**: While it stores glucose as glycogen in response to insulin, it does not produce insulin itself. 3. **Pituitary**: Known as the 'master gland,' it produces hormones that regulate other glands (like Growth Hormone or TSH), but not insulin. Therefore, the correct answer is the Pancreas.