How useful are serum ACE, IgG4, and antipituitary antibody (APA) levels for diagnosing hypophysitis?
Sarcoidosis and IgG4-related diseases generally require a tissue sample for diagnosis. A serum or CSF ACE level is a highly specific (95%), but insensitive (25%–76%) marker for neurosarcoidosis. Similarly, for IgG4 hypophysitis, elevated serum/CSF concentrations of IgG4 are found in only ≈ 70% of patients. Lastly, investigations of APAs and antihypothalamus antibodies have been studied, but these tests currently have insufficient sensitivities and specificities for diagnostic utility.
In general, the diagnosis of hypophysitis is difficult as no preoperative laboratory test currently exists. In most cases, the diagnosis is suspected/presumed, and definitive diagnosis of hypophysitis, particularly if indicated by progressive disease, is determined through histologic examination of biopsied tissue.