A full list of homeostatic malfunctions would be very long, so I will address the three items in your second sentence.
The regulation of blood glucose is critical to the well being of humans. The principal control mechanism is the production of insulin, which is secreted by the pancreas gland. Elevated blood sugar is the result of low or absent insulin levels, or the inability to properly utilize insulin. That condition will result in diabetes, which will lead to several problems, including blindness, nerve damage, and heart problems, just to mention a few conditions.
Temperature control is a fundamental mechanism, and humans must maintain a narrow temperature range, about 95 - 101oF. Beyond that range, severe problems will result, often death. Having a fever (high temperature) is a well known medical problem, which, if unchecked, will result in brain damage.
Clearly, water regulation is important, but here the tolerance range is wider than in the other two items. A human can survive without water for about three days, after which time severe dehydration will occur leading to rapid pulse, elevated blood pressure, and extreme fatigue.
There are other conditions which will occur when any of these mechanisms are out of control, but I hope that this brief response to your inquiry will help you.
