Dehydration
Dehydration is a mild sign of hyperparathyroidism. This can be caused by many reasons. Firstly, the condition causes you to urinate more frequently to eliminate excess calcium, meaning quicker losses of fluids. This triggers your brain to send signals and make you feel thirsty to compensate for the loss. Another cause is that the buildup of calcium in the blood would slow down your metabolic rate. As such, your body will need more water to perform some basic functions as usual. [4]
