I’m the med tech who runs these tests and TRH is a blood test determining the amount of TSH following administration of thyrotropin releasing hormone.Patients with primary hypothyroidism have a high basal serum TSH d an exaggerated resonse to TRH when administered. I graduated from college in 1970 and we were doing the test then so it’s not new but, with all the newer tets it’s not as diagnostically significant.