Hyperparathyroidism is a condtion where the parathyroid glands in the neck secrete excess amount of PTH (parathyroid hormone). There are two main causes - primary hyperparathyroidism, which is usually due to a benign parathyroid tumour; and secondary hyperparathyroidism - which is due to vitamin D/calcium deficiency or kidney disease. The treatment for the former is surgery, while for the latter it is medical. There are features of bone pain (sometimes fractures) and muscle weakness in both types, but other features like renal stones are unique to primary hyperparathyroidism. The main difference is in the blood calcium level - in primary it is high, while in secondary it is it usually normal or sometimes low.