According to this article:

http://www.vetcentric.com/reference/displayFAQ.cfm?ARTICLE=Is%20hypercalcemia%20
a%20disease%3F

As far as prognosis goes (but do read the whole article)  - it says:

"The prognosis for recovery depends on the underlying cause of the
hypercalcemia and how damaging the high calcium levels were to the kidneys,
heart, and other organs. Lymphosarcoma and other cancers carry a guarded to
poor prognosis, while primary hyperparathyroidism is frequently cured with
surgery or newer treatments."

Judy