Hyperparathyroidism is the first disorder comes to mind. My girlfriends mom just got one enlarged (benign) gland removed 2 days ago. She was misdiagnosed (pretty common of course) as fibromyalgia.
The parathyroid glands are small endocrine glands in the neck that produce parathyroid hormone. Humans usually have four parathyroid glands, which are usually located on the rear surface of the thyroid gland, or, in rare cases, within the thyroid gland itself or in the chest. Parathyroid glands control the amount of calcium in the blood and within the bones
Also 2 vitamins are responsible to make sure calcium are in the bones. D and K. So of course with above disorder patients are D deficient as well.