Thyrotropin Releasing Hormone Stimulation Test
TRH stimulation is helpful in identifying a minority of patients who are thought to have hyperthyroidism, or hypothyroidism, but who have insufficient laboratory evidence for a firm diagnosis. An intravenous 200-500 ug dose of synthetic TRH is given to stimulate the release of TSH. The test is performed in the morning, after an overnight fast. Samples for TSH are drawn just before, 30 minutes, and 60 minutes, following the administration. of the TRH. The minimal normal response is usually considered to be an increase over baseline of 2 uIU/L. Responses between 1 and 2 uIU/L are borderline. The response to TRH may be suppressed in men over age 40, in nonthyroid illness, in patients with depression, or adrenal cortex hyper-function.
