Currently, the most prevalent assay for PTH is the intact PTH assay, which typically measures the whole molecule (PTH 1-84) and the larger fragments (predominantly PTH 1-74). While this assay is known as the "intact" assay, it measures large fragments that are slightly smaller than the truly intact hormone. There are less common but newer assays that detect only the whole molecule, which has the greatest bioactivity. The "intact" and "whole or bioactive" assays have different reference ranges, but typically their results yield similar interpretations. The effects of fragmentation and disease are still being studied, and there are instances when the two assays may yield a different interpretation.
This topic will review the pharmacology of sulfasalazine and 5-ASAs, mechanism of action in inflammatory bowel disease, and side effects. The role of sulfasalazine and 5-ASAs in the treatment of inflammatory bowel disease and rheumatoid arthritis are discussed in detail separately. (See "Overview of the medical management of mild to moderate Crohn disease in adults" and "Management of mild to moderate ulcerative colitis in adults" and "Management of severe ulcerative colitis in adults" and "Sulfasalazine in the treatment of rheumatoid arthritis" .)