Primary Hyperparathyroidism: This condition is characterized by the overproduction of parathyroid hormone (PTH), leading to elevated calcium levels. ALP can also be elevated, especially in cases where there is bone involvement.

Vitamin D toxicity: Excessive intake of vitamin D can lead to increased absorption of calcium from the gut, resulting in hypercalcemia. ALP may also be elevated due to the effect of vitamin D on bone metabolism.
Paget's disease of bone: This condition involves an abnormal breakdown and regrowth of bone tissue, leading to elevated ALP levels. Hypercalcemia can occur, especially if there is significant bone resorption.
Hyperthyroidism: Although less common, hyperthyroidism can cause an increase in bone turnover, leading to elevated ALP and, in some cases, hypercalcemia.

Malignancy-associated hypercalcemia: Various cancers, such as multiple myeloma, lung cancer, and breast cancer, can produce substances that lead to hypercalcemia. ALP may be elevated in cases where there is bone metastasis. Missing this diagnosis could be fatal due to the underlying cancer.
Sarcoidosis: This condition can cause an increase in vitamin D production, leading to hypercalcemia. ALP may also be elevated, particularly if there is liver involvement.

Familial hypocalciuric hypercalcemia (FHH): A rare genetic disorder that affects calcium sensing and leads to hypercalcemia. ALP may be elevated in some cases.
Juvenile hyperparathyroidism: A rare condition that presents with hyperparathyroidism in children, leading to elevated calcium and potentially ALP levels.
Osteoblastic metastases: Certain cancers, like prostate cancer, can metastasize to bone and cause an osteoblastic response, leading to elevated ALP and, in some cases, hypercalcemia.