What is a common paraneoplastic syndrome associated with lung cancer?

The correct answer is hypercalcemia, which is a common paraneoplastic syndrome associated with lung cancer, particularly with squamous cell carcinoma of the lungs. This occurs due to the production of parathyroid hormone-related peptide (PTHrP) by tumor cells, which mimics the action of parathyroid hormone (PTH) and leads to increased mobilization of calcium from the bones into the bloodstream. As a result, patients may present with symptoms of hypercalcemia, such as fatigue, confusion, increased thirst, and frequent urination.

The context of the other options provides useful insight into why they are not associated with lung cancer in the same way. Hyperthyroidism is not typically linked with lung cancers and is more commonly related to autoimmune conditions like Graves' disease. Hypoglycemia, while it can occur in various malignancies, is not a common paraneoplastic syndrome specifically associated with lung cancer. Anemia can be observed as a systemic effect of chronic disease and may occur in various cancers, but it is not classified as a paraneoplastic syndrome in the same context as hypercalcemia is for lung cancer.