What is the role of increased 1,25-OH D3 in certain malignancies?

Increased levels of 1,25-dihydroxyvitamin D3, also known as calcitriol, play a significant role in certain malignancies, particularly in promoting hypercalcemia. In malignancies such as lymphoma and certain solid tumors, the production of excessive amounts of 1,25-OH D3 occurs, which can be a paraneoplastic syndrome. This increased level of calcitriol enhances intestinal absorption of calcium, mobilizes calcium from bones, and reduces renal excretion of calcium, all contributing to elevated serum calcium levels, or hypercalcemia.

Hypercalcemia is a common laboratory finding in patients with malignancy and can lead to a variety of clinical symptoms, including nausea, vomiting, constipation, altered mental status, and even cardiac arrhythmias if left untreated. Understanding these mechanisms is important for recognizing and managing paraneoplastic syndromes within the context of cancer care.