1. Sources: Dairy products, nuts, beans, seeds, green leafy vegetables.
2. Hormones: PTH leads to increased levels of circulating calcium by releasing it from the bones, reducing calcium excretion by kidney, and by increasing dietary absorbtion of the calcium through activation of vitamin D.
a. Causes: Lack of dietary calcium, low PTH hormone levels, vitamin D deficiency, hypoalbuminemia, chornic renal failure, and hypomagnesemia.
b. Symptoms: Paresthesias, tingling sensations, muscle spasms. Cardiac arrythmias, increased QT intervals. Osteoporosis.
4. Excess calcium: Generally indicative of underlying disease process.
a. Causes: Excess PTH due to parathyroid tumors, various cancers, chronic renal disease, disorders of Vitamin D metabolism, granulomatous diseases, and disorders of excess bone turnover.
Symptoms: "Painful bones, renal stones, abdominal groans, and psychic moans". Some symptoms caused by dehydration as kidney tries to excrete calcium (which requires water). This causes fatigue, nausea, and vomiting. Various neuro, muscular, and cardiac abnormalities appear (bradycardia, cardiac block, shortened QT, longer T wave).