<qa>  What is the name of the drug used for diagnosing and evaluating patients with thyroid gland abnormalThis study will determine the safety and activity of a new formulation of thyrotropin-releasing hormone TRH, a drug used for diagnosing and evaluating patients with certain thyroid gland abnormalities. Normal thyroid gland function depends on proper chemical signaling between the thyroid gland, the hypothalamus the part of the brain where TRH is made, and the pituitary another part of the brain. The TRH test helps assess this interaction. Production of the only FDA-approved preparation of TRH was stopped in July 2002. As a result, to have a continuous source of TRH available for NIH clinical and research purposes, the NIH Clinical Center CC Pharmacy Department produced a pharmaceutical grade formulation of TRH for patient use. This study will test the CC formulation in healthy volunteers to show that its activity and side effects are similar to those of the previously available commercial test preparation. It will then be studied in CC patients for whom the diagnostic test is recommended. 