Insulin insufficiency leads to which of the following symptoms?

Insulin insufficiency is primarily associated with the body's inability to effectively utilize glucose, leading to higher blood sugar levels. When insulin levels are inadequate, the body seeks alternative sources of energy, which can manifest as increased appetite. As the body cannot efficiently transport glucose into the cells for energy, there's also a physiological response that leads to increased thirst. This is partly due to the osmotic diuresis caused by elevated blood glucose levels, which results in excessive urination and dehydration, further driving the feeling of thirst.

This symptom of increased appetite and thirst is particularly prominent in conditions such as diabetes mellitus, where an insufficient insulin response directly correlates with these signs. The body's attempt to compensate for low insulin by signaling hunger and thirst illustrates how insulin deficiency impacts metabolic processes and homeostasis.

In contrast, other symptoms listed in the alternative choices do not align with the typical presentation of insulin insufficiency. For instance, extreme fatigue and weight gain, decreased urination and hypoglycemia, or severe headaches and vision changes may arise from various metabolic, hormonal, or acute medical conditions, but they are not direct symptoms of insulin insufficiency itself. Hence, focusing on increased appetite and thirst provides a clear and relevant understanding of the physiological effects of insulin insufficiency.