Final answer:
The hormone involved in diabetes mellitus, where either its secretion or response is inadequate, is insulin. Insulin is crucial for lowering blood glucose levels by facilitating cellular uptake. Type I diabetes is a result of insulin hyposecretion and requires insulin injections for management.
Step-by-step explanation:
Diabetes mellitus occurs when either the secretion or the response to the hormone insulin is inadequate. Insulin is produced by the pancreas and is crucial for regulating blood glucose levels. When blood glucose levels rise, insulin facilitates the uptake of glucose into cells and helps maintain normal blood sugar levels. Diabetes mellitus manifests as high blood glucose levels, or hyperglycemia, due to the body's inability to properly use or produce enough insulin. In contrast, glucagon is a different hormone released by the pancreas that raises blood glucose levels when they are too low.
Type I diabetes, also known as insulin-dependent diabetes, is characterized by the destruction of insulin-producing cells in the pancreas, which is often an autoimmune response, making it a hyposecretion condition where insulin is substantially deficient or absent. As a result, individuals with Type I diabetes require regular insulin injections to manage their blood glucose levels.