In particular, among the most common laboratory tests used are those for vitamin B12 levels (to rule out subacute combined degeneration), parathyroid hormone levels (to rule out hyperparathyroidism), and serum protein electrophoresis with immunofixation (to rule out multiple myeloma or monoclonal gammopathy of undetermined significance (MGUS)). The gene discussed is PTH; the disease is hyperparathyroidism.